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class="vector-toc-text"> <span class="vector-toc-numb">2</span> <span>Muon sources</span> </div> </a> <ul id="toc-Muon_sources-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Muon_decay" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Muon_decay"> <div class="vector-toc-text"> <span class="vector-toc-numb">3</span> <span>Muon decay</span> </div> </a> <button aria-controls="toc-Muon_decay-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Muon decay subsection</span> </button> <ul id="toc-Muon_decay-sublist" class="vector-toc-list"> <li id="toc-Prohibited_decays" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Prohibited_decays"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.1</span> <span>Prohibited decays</span> </div> </a> <ul id="toc-Prohibited_decays-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Theoretical_decay_rate" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Theoretical_decay_rate"> <div class="vector-toc-text"> <span class="vector-toc-numb">3.2</span> <span>Theoretical decay rate</span> </div> </a> <ul id="toc-Theoretical_decay_rate-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Muonic_atoms" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Muonic_atoms"> <div class="vector-toc-text"> <span class="vector-toc-numb">4</span> <span>Muonic atoms</span> </div> </a> <button aria-controls="toc-Muonic_atoms-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Muonic atoms subsection</span> </button> <ul id="toc-Muonic_atoms-sublist" class="vector-toc-list"> <li id="toc-Negative_muon_atoms" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Negative_muon_atoms"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.1</span> <span>Negative muon atoms</span> </div> </a> <ul id="toc-Negative_muon_atoms-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Positive_muon_atoms" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Positive_muon_atoms"> <div class="vector-toc-text"> <span class="vector-toc-numb">4.2</span> <span>Positive muon atoms</span> </div> </a> <ul id="toc-Positive_muon_atoms-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Anomalous_magnetic_dipole_moment" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Anomalous_magnetic_dipole_moment"> <div class="vector-toc-text"> <span class="vector-toc-numb">5</span> <span>Anomalous magnetic dipole moment</span> </div> </a> <button aria-controls="toc-Anomalous_magnetic_dipole_moment-sublist" class="cdx-button cdx-button--weight-quiet cdx-button--icon-only vector-toc-toggle"> <span class="vector-icon mw-ui-icon-wikimedia-expand"></span> <span>Toggle Anomalous magnetic dipole moment subsection</span> </button> <ul id="toc-Anomalous_magnetic_dipole_moment-sublist" class="vector-toc-list"> <li id="toc-Muon_g−2" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#Muon_g−2"> <div class="vector-toc-text"> <span class="vector-toc-numb">5.1</span> <span>Muon g−2</span> </div> </a> <ul id="toc-Muon_g−2-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-Electric_dipole_moment" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Electric_dipole_moment"> <div class="vector-toc-text"> <span class="vector-toc-numb">6</span> <span>Electric dipole moment</span> </div> </a> <ul id="toc-Electric_dipole_moment-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Muon_radiography_and_tomography" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Muon_radiography_and_tomography"> <div class="vector-toc-text"> <span class="vector-toc-numb">7</span> <span>Muon radiography and tomography</span> </div> </a> <ul id="toc-Muon_radiography_and_tomography-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-See_also" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#See_also"> <div class="vector-toc-text"> <span class="vector-toc-numb">8</span> <span>See also</span> </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-References" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#References"> <div class="vector-toc-text"> <span class="vector-toc-numb">9</span> <span>References</span> </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Further_reading" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Further_reading"> <div class="vector-toc-text"> <span class="vector-toc-numb">10</span> <span>Further reading</span> </div> </a> <ul id="toc-Further_reading-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-External_links" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#External_links"> <div class="vector-toc-text"> <span class="vector-toc-numb">11</span> <span>External links</span> </div> </a> <ul id="toc-External_links-sublist" class="vector-toc-list"> </ul> </li> </ul> </div> </div> </nav> </div> </div> <div class="mw-content-container"> <main id="content" class="mw-body"> <header class="mw-body-header vector-page-titlebar"> <nav aria-label="Contents" class="vector-toc-landmark"> <div id="vector-page-titlebar-toc" class="vector-dropdown vector-page-titlebar-toc vector-button-flush-left" title="Table of Contents" > <input type="checkbox" id="vector-page-titlebar-toc-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-vector-page-titlebar-toc" class="vector-dropdown-checkbox " aria-label="Toggle the table of contents" > <label id="vector-page-titlebar-toc-label" for="vector-page-titlebar-toc-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--icon-only " aria-hidden="true" ><span class="vector-icon mw-ui-icon-listBullet mw-ui-icon-wikimedia-listBullet"></span> <span class="vector-dropdown-label-text">Toggle the table of contents</span> </label> <div class="vector-dropdown-content"> <div id="vector-page-titlebar-toc-unpinned-container" class="vector-unpinned-container"> </div> </div> </div> </nav> <h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Muon</span></h1> <div id="p-lang-btn" class="vector-dropdown mw-portlet mw-portlet-lang" > <input type="checkbox" id="p-lang-btn-checkbox" role="button" aria-haspopup="true" data-event-name="ui.dropdown-p-lang-btn" class="vector-dropdown-checkbox mw-interlanguage-selector" aria-label="Go to an article in another language. Available in 72 languages" > <label id="p-lang-btn-label" for="p-lang-btn-checkbox" class="vector-dropdown-label cdx-button cdx-button--fake-button cdx-button--fake-button--enabled cdx-button--weight-quiet cdx-button--action-progressive mw-portlet-lang-heading-72" aria-hidden="true" ><span class="vector-icon mw-ui-icon-language-progressive mw-ui-icon-wikimedia-language-progressive"></span> <span class="vector-dropdown-label-text">72 languages</span> </label> <div class="vector-dropdown-content"> <div class="vector-menu-content"> <ul class="vector-menu-content-list"> <li class="interlanguage-link interwiki-af mw-list-item"><a href="https://af.wikipedia.org/wiki/Muon" title="Muon – Afrikaans" lang="af" hreflang="af" data-title="Muon" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target"><span>Afrikaans</span></a></li><li class="interlanguage-link interwiki-als mw-list-item"><a href="https://als.wikipedia.org/wiki/Myon" title="Myon – Alemannic" lang="gsw" hreflang="gsw" data-title="Myon" data-language-autonym="Alemannisch" data-language-local-name="Alemannic" class="interlanguage-link-target"><span>Alemannisch</span></a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%85%D9%8A%D9%88%D9%88%D9%86" title="ميوون – Arabic" lang="ar" hreflang="ar" data-title="ميوون" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target"><span>العربية</span></a></li><li class="interlanguage-link interwiki-ast mw-list-item"><a href="https://ast.wikipedia.org/wiki/Muon" title="Muon – Asturian" lang="ast" hreflang="ast" data-title="Muon" data-language-autonym="Asturianu" data-language-local-name="Asturian" class="interlanguage-link-target"><span>Asturianu</span></a></li><li class="interlanguage-link interwiki-az mw-list-item"><a href="https://az.wikipedia.org/wiki/Myuon" title="Myuon – Azerbaijani" lang="az" hreflang="az" data-title="Myuon" data-language-autonym="Azərbaycanca" data-language-local-name="Azerbaijani" class="interlanguage-link-target"><span>Azərbaycanca</span></a></li><li class="interlanguage-link interwiki-bn mw-list-item"><a href="https://bn.wikipedia.org/wiki/%E0%A6%AE%E0%A6%BF%E0%A6%89%E0%A6%AF%E0%A6%BC%E0%A6%A8" title="মিউয়ন – Bangla" lang="bn" hreflang="bn" data-title="মিউয়ন" data-language-autonym="বাংলা" data-language-local-name="Bangla" class="interlanguage-link-target"><span>বাংলা</span></a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%9C%D1%8E%D0%BE%D0%BD" title="Мюон – Belarusian" lang="be" hreflang="be" data-title="Мюон" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target"><span>Беларуская</span></a></li><li class="interlanguage-link interwiki-bg mw-list-item"><a href="https://bg.wikipedia.org/wiki/%D0%9C%D1%8E%D0%BE%D0%BD" title="Мюон – Bulgarian" lang="bg" hreflang="bg" data-title="Мюон" data-language-autonym="Български" data-language-local-name="Bulgarian" class="interlanguage-link-target"><span>Български</span></a></li><li class="interlanguage-link interwiki-bs mw-list-item"><a href="https://bs.wikipedia.org/wiki/Mion" title="Mion – Bosnian" lang="bs" hreflang="bs" data-title="Mion" data-language-autonym="Bosanski" data-language-local-name="Bosnian" class="interlanguage-link-target"><span>Bosanski</span></a></li><li class="interlanguage-link interwiki-br mw-list-item"><a href="https://br.wikipedia.org/wiki/Muon" title="Muon – Breton" lang="br" hreflang="br" data-title="Muon" data-language-autonym="Brezhoneg" data-language-local-name="Breton" class="interlanguage-link-target"><span>Brezhoneg</span></a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Mu%C3%B3" title="Muó – Catalan" lang="ca" hreflang="ca" data-title="Muó" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target"><span>Català</span></a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Mion" title="Mion – Czech" lang="cs" hreflang="cs" data-title="Mion" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target"><span>Čeština</span></a></li><li class="interlanguage-link interwiki-co mw-list-item"><a href="https://co.wikipedia.org/wiki/Muonu" title="Muonu – Corsican" lang="co" hreflang="co" data-title="Muonu" data-language-autonym="Corsu" data-language-local-name="Corsican" class="interlanguage-link-target"><span>Corsu</span></a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Myon" title="Myon – Danish" lang="da" hreflang="da" data-title="Myon" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target"><span>Dansk</span></a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Myon" title="Myon – German" lang="de" hreflang="de" data-title="Myon" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target"><span>Deutsch</span></a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/M%C3%BC%C3%BCon" title="Müüon – Estonian" lang="et" hreflang="et" data-title="Müüon" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target"><span>Eesti</span></a></li><li class="interlanguage-link interwiki-el mw-list-item"><a href="https://el.wikipedia.org/wiki/%CE%9C%CE%B9%CF%8C%CE%BD%CE%B9%CE%BF" title="Μιόνιο – Greek" lang="el" hreflang="el" data-title="Μιόνιο" data-language-autonym="Ελληνικά" data-language-local-name="Greek" class="interlanguage-link-target"><span>Ελληνικά</span></a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Muon" title="Muon – Spanish" lang="es" hreflang="es" data-title="Muon" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target"><span>Español</span></a></li><li class="interlanguage-link interwiki-eo mw-list-item"><a href="https://eo.wikipedia.org/wiki/Muono" title="Muono – Esperanto" lang="eo" hreflang="eo" data-title="Muono" data-language-autonym="Esperanto" data-language-local-name="Esperanto" class="interlanguage-link-target"><span>Esperanto</span></a></li><li class="interlanguage-link interwiki-eu mw-list-item"><a href="https://eu.wikipedia.org/wiki/Muoi" title="Muoi – Basque" lang="eu" hreflang="eu" data-title="Muoi" data-language-autonym="Euskara" data-language-local-name="Basque" class="interlanguage-link-target"><span>Euskara</span></a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%D9%85%DB%8C%D9%88%D9%86" title="میون – Persian" lang="fa" hreflang="fa" data-title="میون" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target"><span>فارسی</span></a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Muon" title="Muon – French" lang="fr" hreflang="fr" data-title="Muon" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target"><span>Français</span></a></li><li class="interlanguage-link interwiki-ga mw-list-item"><a href="https://ga.wikipedia.org/wiki/Mu%C3%B3n" title="Muón – Irish" lang="ga" hreflang="ga" data-title="Muón" data-language-autonym="Gaeilge" data-language-local-name="Irish" class="interlanguage-link-target"><span>Gaeilge</span></a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Mu%C3%B3n" title="Muón – Galician" lang="gl" hreflang="gl" data-title="Muón" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target"><span>Galego</span></a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EB%AE%A4%EC%98%A8" title="뮤온 – Korean" lang="ko" hreflang="ko" data-title="뮤온" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target"><span>한국어</span></a></li><li class="interlanguage-link interwiki-hy mw-list-item"><a href="https://hy.wikipedia.org/wiki/%D5%84%D5%B5%D5%B8%D6%82%D5%B8%D5%B6" title="Մյուոն – Armenian" lang="hy" hreflang="hy" data-title="Մյուոն" data-language-autonym="Հայերեն" data-language-local-name="Armenian" class="interlanguage-link-target"><span>Հայերեն</span></a></li><li class="interlanguage-link interwiki-hi mw-list-item"><a href="https://hi.wikipedia.org/wiki/%E0%A4%AE%E0%A5%8D%E0%A4%AF%E0%A5%82%E0%A4%91%E0%A4%A8" title="म्यूऑन – Hindi" lang="hi" hreflang="hi" data-title="म्यूऑन" data-language-autonym="हिन्दी" data-language-local-name="Hindi" class="interlanguage-link-target"><span>हिन्दी</span></a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Mion" title="Mion – Croatian" lang="hr" hreflang="hr" data-title="Mion" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target"><span>Hrvatski</span></a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Muon" title="Muon – Indonesian" lang="id" hreflang="id" data-title="Muon" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target"><span>Bahasa Indonesia</span></a></li><li class="interlanguage-link interwiki-ia mw-list-item"><a href="https://ia.wikipedia.org/wiki/Muon" title="Muon – Interlingua" lang="ia" hreflang="ia" data-title="Muon" data-language-autonym="Interlingua" data-language-local-name="Interlingua" class="interlanguage-link-target"><span>Interlingua</span></a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Muone" title="Muone – Italian" lang="it" hreflang="it" data-title="Muone" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target"><span>Italiano</span></a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%9E%D7%99%D7%95%D7%90%D7%95%D7%9F" title="מיואון – Hebrew" lang="he" hreflang="he" data-title="מיואון" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target"><span>עברית</span></a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%9B%E1%83%98%E1%83%A3%E1%83%9D%E1%83%9C%E1%83%98" title="მიუონი – Georgian" lang="ka" hreflang="ka" data-title="მიუონი" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target"><span>ქართული</span></a></li><li class="interlanguage-link interwiki-kk mw-list-item"><a href="https://kk.wikipedia.org/wiki/%D0%9C%D1%8E%D0%BE%D0%BD" title="Мюон – Kazakh" lang="kk" hreflang="kk" data-title="Мюон" data-language-autonym="Қазақша" data-language-local-name="Kazakh" class="interlanguage-link-target"><span>Қазақша</span></a></li><li class="interlanguage-link interwiki-la mw-list-item"><a href="https://la.wikipedia.org/wiki/Myon" title="Myon – Latin" lang="la" hreflang="la" data-title="Myon" data-language-autonym="Latina" data-language-local-name="Latin" class="interlanguage-link-target"><span>Latina</span></a></li><li class="interlanguage-link interwiki-lv mw-list-item"><a href="https://lv.wikipedia.org/wiki/Mions" title="Mions – Latvian" lang="lv" hreflang="lv" data-title="Mions" data-language-autonym="Latviešu" data-language-local-name="Latvian" class="interlanguage-link-target"><span>Latviešu</span></a></li><li class="interlanguage-link interwiki-lt mw-list-item"><a href="https://lt.wikipedia.org/wiki/Miuonas" title="Miuonas – Lithuanian" lang="lt" hreflang="lt" data-title="Miuonas" data-language-autonym="Lietuvių" data-language-local-name="Lithuanian" class="interlanguage-link-target"><span>Lietuvių</span></a></li><li class="interlanguage-link interwiki-li mw-list-item"><a href="https://li.wikipedia.org/wiki/Muon" title="Muon – Limburgish" lang="li" hreflang="li" data-title="Muon" data-language-autonym="Limburgs" data-language-local-name="Limburgish" class="interlanguage-link-target"><span>Limburgs</span></a></li><li class="interlanguage-link interwiki-lmo mw-list-item"><a href="https://lmo.wikipedia.org/wiki/Mu%C3%BAn" title="Muún – Lombard" lang="lmo" hreflang="lmo" data-title="Muún" data-language-autonym="Lombard" data-language-local-name="Lombard" class="interlanguage-link-target"><span>Lombard</span></a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/M%C3%BCon" title="Müon – Hungarian" lang="hu" hreflang="hu" data-title="Müon" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target"><span>Magyar</span></a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%9C%D0%B8%D0%BE%D0%BD" title="Мион – Macedonian" lang="mk" hreflang="mk" data-title="Мион" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target"><span>Македонски</span></a></li><li class="interlanguage-link interwiki-ml mw-list-item"><a href="https://ml.wikipedia.org/wiki/%E0%B4%AE%E0%B5%8D%E0%B4%AF%E0%B5%82%E0%B4%93%E0%B5%BA" title="മ്യൂഓൺ – Malayalam" lang="ml" hreflang="ml" data-title="മ്യൂഓൺ" data-language-autonym="മലയാളം" data-language-local-name="Malayalam" class="interlanguage-link-target"><span>മലയാളം</span></a></li><li class="interlanguage-link interwiki-mr mw-list-item"><a href="https://mr.wikipedia.org/wiki/%E0%A4%AE%E0%A5%8D%E0%A4%AF%E0%A5%82%E0%A4%91%E0%A4%A8" title="म्यूऑन – Marathi" lang="mr" hreflang="mr" data-title="म्यूऑन" data-language-autonym="मराठी" data-language-local-name="Marathi" class="interlanguage-link-target"><span>मराठी</span></a></li><li class="interlanguage-link interwiki-ms mw-list-item"><a href="https://ms.wikipedia.org/wiki/Muon" title="Muon – Malay" lang="ms" hreflang="ms" data-title="Muon" data-language-autonym="Bahasa Melayu" data-language-local-name="Malay" class="interlanguage-link-target"><span>Bahasa Melayu</span></a></li><li class="interlanguage-link interwiki-my mw-list-item"><a href="https://my.wikipedia.org/wiki/%E1%80%99%E1%80%BB%E1%80%B0%E1%80%9A%E1%80%BD%E1%80%94%E1%80%BA" title="မျူယွန် – Burmese" lang="my" hreflang="my" data-title="မျူယွန်" data-language-autonym="မြန်မာဘာသာ" data-language-local-name="Burmese" class="interlanguage-link-target"><span>မြန်မာဘာသာ</span></a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Muon" title="Muon – Dutch" lang="nl" hreflang="nl" data-title="Muon" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target"><span>Nederlands</span></a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/%E3%83%9F%E3%83%A5%E3%83%BC%E7%B2%92%E5%AD%90" title="ミュー粒子 – Japanese" lang="ja" hreflang="ja" data-title="ミュー粒子" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target"><span>日本語</span></a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Myon" title="Myon – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Myon" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target"><span>Norsk bokmål</span></a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Myon" title="Myon – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Myon" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target"><span>Norsk nynorsk</span></a></li><li class="interlanguage-link interwiki-oc mw-list-item"><a href="https://oc.wikipedia.org/wiki/Muon" title="Muon – Occitan" lang="oc" hreflang="oc" data-title="Muon" data-language-autonym="Occitan" data-language-local-name="Occitan" class="interlanguage-link-target"><span>Occitan</span></a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%D9%85%DB%8C%D9%88%D9%86" title="میون – Western Punjabi" lang="pnb" hreflang="pnb" data-title="میون" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target"><span>پنجابی</span></a></li><li class="interlanguage-link interwiki-nds mw-list-item"><a href="https://nds.wikipedia.org/wiki/Myon" title="Myon – Low German" lang="nds" hreflang="nds" data-title="Myon" data-language-autonym="Plattdüütsch" data-language-local-name="Low German" class="interlanguage-link-target"><span>Plattdüütsch</span></a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Mion" title="Mion – Polish" lang="pl" hreflang="pl" data-title="Mion" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target"><span>Polski</span></a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/Mu%C3%A3o" title="Muão – Portuguese" lang="pt" hreflang="pt" data-title="Muão" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target"><span>Português</span></a></li><li class="interlanguage-link interwiki-ro mw-list-item"><a href="https://ro.wikipedia.org/wiki/Miuon" title="Miuon – Romanian" lang="ro" hreflang="ro" data-title="Miuon" data-language-autonym="Română" data-language-local-name="Romanian" class="interlanguage-link-target"><span>Română</span></a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9C%D1%8E%D0%BE%D0%BD" title="Мюон – Russian" lang="ru" hreflang="ru" data-title="Мюон" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target"><span>Русский</span></a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Muon" title="Muon – Simple English" lang="en-simple" hreflang="en-simple" data-title="Muon" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target"><span>Simple English</span></a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Mi%C3%B3n" title="Mión – Slovak" lang="sk" hreflang="sk" data-title="Mión" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target"><span>Slovenčina</span></a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Mion" title="Mion – Slovenian" lang="sl" hreflang="sl" data-title="Mion" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target"><span>Slovenščina</span></a></li><li class="interlanguage-link interwiki-sr mw-list-item"><a href="https://sr.wikipedia.org/wiki/%D0%9C%D0%B8%D0%BE%D0%BD" title="Мион – Serbian" lang="sr" hreflang="sr" data-title="Мион" data-language-autonym="Српски / srpski" data-language-local-name="Serbian" class="interlanguage-link-target"><span>Српски / srpski</span></a></li><li class="interlanguage-link interwiki-sh mw-list-item"><a href="https://sh.wikipedia.org/wiki/Mion" title="Mion – Serbo-Croatian" lang="sh" hreflang="sh" data-title="Mion" data-language-autonym="Srpskohrvatski / српскохрватски" data-language-local-name="Serbo-Croatian" class="interlanguage-link-target"><span>Srpskohrvatski / српскохрватски</span></a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Myoni" title="Myoni – Finnish" lang="fi" hreflang="fi" data-title="Myoni" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target"><span>Suomi</span></a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Myon" title="Myon – Swedish" lang="sv" hreflang="sv" data-title="Myon" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target"><span>Svenska</span></a></li><li class="interlanguage-link interwiki-tl mw-list-item"><a href="https://tl.wikipedia.org/wiki/Muon" title="Muon – Tagalog" lang="tl" hreflang="tl" data-title="Muon" data-language-autonym="Tagalog" data-language-local-name="Tagalog" class="interlanguage-link-target"><span>Tagalog</span></a></li><li class="interlanguage-link interwiki-ta mw-list-item"><a href="https://ta.wikipedia.org/wiki/%E0%AE%AE%E0%AE%BF%E0%AE%AF%E0%AF%82%E0%AE%B5%E0%AF%8B%E0%AE%A9%E0%AF%8D" title="மியூவோன் – Tamil" lang="ta" hreflang="ta" data-title="மியூவோன்" data-language-autonym="தமிழ்" data-language-local-name="Tamil" class="interlanguage-link-target"><span>தமிழ்</span></a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/M%C3%BCon" title="Müon – Turkish" lang="tr" hreflang="tr" data-title="Müon" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target"><span>Türkçe</span></a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%9C%D1%8E%D0%BE%D0%BD" title="Мюон – Ukrainian" lang="uk" hreflang="uk" data-title="Мюон" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target"><span>Українська</span></a></li><li class="interlanguage-link interwiki-vi mw-list-item"><a href="https://vi.wikipedia.org/wiki/Muon" title="Muon – Vietnamese" lang="vi" hreflang="vi" data-title="Muon" data-language-autonym="Tiếng Việt" data-language-local-name="Vietnamese" class="interlanguage-link-target"><span>Tiếng Việt</span></a></li><li class="interlanguage-link interwiki-war mw-list-item"><a href="https://war.wikipedia.org/wiki/Muon" title="Muon – Waray" lang="war" hreflang="war" data-title="Muon" data-language-autonym="Winaray" data-language-local-name="Waray" class="interlanguage-link-target"><span>Winaray</span></a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/%CE%9C%E5%AD%90" title="Μ子 – Wu" lang="wuu" hreflang="wuu" data-title="Μ子" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target"><span>吴语</span></a></li><li class="interlanguage-link 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class="vector-body" aria-labelledby="firstHeading" data-mw-ve-target-container> <div class="vector-body-before-content"> <div class="mw-indicators"> </div> <div id="siteSub" class="noprint">From Wikipedia, the free encyclopedia</div> </div> <div id="contentSub"><div id="mw-content-subtitle"></div></div> <div id="mw-content-text" class="mw-body-content"><div class="mw-content-ltr mw-parser-output" lang="en" dir="ltr"><div class="shortdescription nomobile noexcerpt noprint searchaux" style="display:none">Subatomic particle</div> <p class="mw-empty-elt"> </p> <style data-mw-deduplicate="TemplateStyles:r1257001546">.mw-parser-output .infobox-subbox{padding:0;border:none;margin:-3px;width:auto;min-width:100%;font-size:100%;clear:none;float:none;background-color:transparent}.mw-parser-output .infobox-3cols-child{margin:auto}.mw-parser-output .infobox .navbar{font-size:100%}@media screen{html.skin-theme-clientpref-night .mw-parser-output .infobox-full-data:not(.notheme)>div:not(.notheme)[style]{background:#1f1f23!important;color:#f8f9fa}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .infobox-full-data:not(.notheme) div:not(.notheme){background:#1f1f23!important;color:#f8f9fa}}@media(min-width:640px){body.skin--responsive .mw-parser-output .infobox-table{display:table!important}body.skin--responsive .mw-parser-output .infobox-table>caption{display:table-caption!important}body.skin--responsive .mw-parser-output .infobox-table>tbody{display:table-row-group}body.skin--responsive .mw-parser-output .infobox-table tr{display:table-row!important}body.skin--responsive .mw-parser-output .infobox-table th,body.skin--responsive .mw-parser-output .infobox-table td{padding-left:inherit;padding-right:inherit}}</style><table class="infobox"><caption class="infobox-title">Muon</caption><tbody><tr><td colspan="2" class="infobox-image"><span class="mw-default-size" typeof="mw:File/Frameless"><a href="/wiki/File:Moon%27s_shadow_in_muons.gif" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/en/thumb/6/6f/Moon%27s_shadow_in_muons.gif/220px-Moon%27s_shadow_in_muons.gif" decoding="async" width="220" height="164" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/6/6f/Moon%27s_shadow_in_muons.gif/330px-Moon%27s_shadow_in_muons.gif 1.5x, //upload.wikimedia.org/wikipedia/en/6/6f/Moon%27s_shadow_in_muons.gif 2x" data-file-width="367" data-file-height="273" /></a></span><div class="infobox-caption">The Moon's <a href="/wiki/Cosmic_ray" title="Cosmic ray">cosmic ray</a> shadow, as seen in secondary muons generated by cosmic rays in the atmosphere, and detected 700 meters below ground, at the <a href="/wiki/Soudan_2" title="Soudan 2">Soudan 2</a> detector</div></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Particle#Composition" title="Particle">Composition</a></th><td class="infobox-data"><a href="/wiki/Elementary_particle" title="Elementary particle">Elementary particle</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Particle_statistics" title="Particle statistics">Statistics</a></th><td class="infobox-data"><a href="/wiki/Fermionic" class="mw-redirect" title="Fermionic">Fermionic</a></td></tr><tr><th scope="row" class="infobox-label">Family</th><td class="infobox-data"><a href="/wiki/Lepton" title="Lepton">Lepton</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Generation_(particle_physics)" title="Generation (particle physics)">Generation</a></th><td class="infobox-data">Second</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Fundamental_interaction" title="Fundamental interaction">Interactions</a></th><td class="infobox-data"><a href="/wiki/Gravity" title="Gravity">Gravity</a>, <a href="/wiki/Electromagnetic_interaction" class="mw-redirect" title="Electromagnetic interaction">electromagnetic</a>, <br /><a href="/wiki/Weak_interaction" title="Weak interaction">weak</a></td></tr><tr><th scope="row" class="infobox-label">Symbol</th><td class="infobox-data"><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Antiparticle" title="Antiparticle">Antiparticle</a></th><td class="infobox-data">Antimuon (<span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">+</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span>)</td></tr><tr><th scope="row" class="infobox-label">Discovered</th><td class="infobox-data"><a href="/wiki/Carl_D._Anderson" class="mw-redirect" title="Carl D. Anderson">Carl D. Anderson</a>, <a href="/wiki/Seth_Neddermeyer" title="Seth Neddermeyer">Seth Neddermeyer</a> (1936)</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Invariant_mass" title="Invariant mass">Mass</a></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="6972188353162700000♠"></span>1.883<span style="margin-left:.25em;">531</span><span style="margin-left:.25em;">627</span>(42)<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−28</sup> kg</span><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span><sup id="cite_ref-physconst-mmu_1-0" class="reference"><a href="#cite_note-physconst-mmu-1"><span class="cite-bracket">[</span>1<span class="cite-bracket">]</span></a></sup><br /><span class="nowrap"><span data-sort-value="6999113428925700000♠"></span>0.113<span style="margin-left:.25em;">428</span><span style="margin-left:.25em;">9257</span>(22) Da</span><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span><sup id="cite_ref-physconst-mmuDa_2-0" class="reference"><a href="#cite_note-physconst-mmuDa-2"><span class="cite-bracket">[</span>2<span class="cite-bracket">]</span></a></sup><br /><span class="nowrap"><span data-sort-value="7002105658375500000♠"></span>105.658<span style="margin-left:.25em;">3755</span>(23) <span class="nowrap"><a href="/wiki/Electronvolt#Mass" title="Electronvolt">MeV/<i>c</i><sup>2</sup></a></span></span><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span><sup id="cite_ref-physconst-mmuc2MeV_3-0" class="reference"><a href="#cite_note-physconst-mmuc2MeV-3"><span class="cite-bracket">[</span>3<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Mean_lifetime" class="mw-redirect" title="Mean lifetime">Mean lifetime</a></th><td class="infobox-data"><span class="nowrap"><span data-sort-value="6994219698110000000♠"></span>2.196<span style="margin-left:.25em;">9811</span>(22)<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−6</sup> <a href="/wiki/Second" title="Second">s</a></span><sup id="cite_ref-PDG2012_4-0" class="reference"><a href="#cite_note-PDG2012-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-PDG2016_5-0" class="reference"><a href="#cite_note-PDG2016-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Particle_decay" title="Particle decay">Decays into</a></th><td class="infobox-data"><a href="/wiki/Electron" title="Electron"><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span></a>, <a href="/wiki/Electron_antineutrino" class="mw-redirect" title="Electron antineutrino"><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span><span style="text-decoration:overline;">ν</span><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">e</sub></span></span></span></a>, <a href="/wiki/Muon_neutrino" title="Muon neutrino"><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>ν<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">μ</sub></span></span></span></a><sup id="cite_ref-PDG2016_5-1" class="reference"><a href="#cite_note-PDG2016-5"><span class="cite-bracket">[</span>5<span class="cite-bracket">]</span></a></sup> (most common)</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Electric_charge" title="Electric charge">Electric charge</a></th><td class="infobox-data">−1 <a href="/wiki/Elementary_charge" title="Elementary charge"><i>e</i></a></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Color_charge" title="Color charge">Color charge</a></th><td class="infobox-data">None</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Spin_(physics)" title="Spin (physics)">Spin</a></th><td class="infobox-data"><style data-mw-deduplicate="TemplateStyles:r1214402035">.mw-parser-output .sfrac{white-space:nowrap}.mw-parser-output .sfrac.tion,.mw-parser-output .sfrac .tion{display:inline-block;vertical-align:-0.5em;font-size:85%;text-align:center}.mw-parser-output .sfrac .num{display:block;line-height:1em;margin:0.0em 0.1em;border-bottom:1px solid}.mw-parser-output .sfrac .den{display:block;line-height:1em;margin:0.1em 0.1em}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}</style><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span> <a href="/wiki/Reduced_Planck_constant" class="mw-redirect" title="Reduced Planck constant"><i>ħ</i></a></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Weak_isospin" title="Weak isospin">Weak isospin</a></th><td class="infobox-data"><span class="nowrap"><a href="/wiki/Chirality_(physics)" title="Chirality (physics)">LH</a>: −<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035" /><span class="sfrac">⁠<span class="tion"><span class="num">1</span><span class="sr-only">/</span><span class="den">2</span></span>⁠</span>, <a href="/wiki/Chirality_(physics)" title="Chirality (physics)">RH</a>: 0</span></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Weak_hypercharge" title="Weak hypercharge">Weak hypercharge</a></th><td class="infobox-data"><span class="nowrap"><a href="/wiki/Chirality_(physics)" title="Chirality (physics)">LH</a>: −1, <a href="/wiki/Chirality_(physics)" title="Chirality (physics)">RH</a>: −2</span></td></tr></tbody></table> <p>A <b>muon</b> (<span class="rt-commentedText nowrap"><span class="IPA nopopups noexcerpt" lang="en-fonipa"><a href="/wiki/Help:IPA/English" title="Help:IPA/English">/<span style="border-bottom:1px dotted"><span title="/ˈ/: primary stress follows">ˈ</span><span title="'m' in 'my'">m</span></span>(<span style="border-bottom:1px dotted"><span title="/j/: 'y' in 'yes'">j</span></span>)<span style="border-bottom:1px dotted"><span title="/uː/: 'oo' in 'goose'">uː</span><span title="/./: syllable break">.</span><span title="/ɒ/: 'o' in 'body'">ɒ</span><span title="'n' in 'nigh'">n</span></span>/</a></span></span> <a href="/wiki/Help:Pronunciation_respelling_key" title="Help:Pronunciation respelling key"><i title="English pronunciation respelling"><span style="font-size:90%">M(Y)OO</span>-on</i></a>; from the <a href="/wiki/Greek_alphabet" title="Greek alphabet">Greek</a> letter <a href="/wiki/Mu_(letter)" title="Mu (letter)">mu</a> (μ) used to represent it) is an <a href="/wiki/Elementary_particle" title="Elementary particle">elementary particle</a> similar to the <a href="/wiki/Electron" title="Electron">electron</a>, with an <a href="/wiki/Electric_charge" title="Electric charge">electric charge</a> of −1 <i><a href="/wiki/Elementary_charge" title="Elementary charge">e</a></i> and <a href="/wiki/Spin-1/2" title="Spin-1/2">spin-1/2</a>, but with a much greater mass. It is classified as a <a href="/wiki/Lepton" title="Lepton">lepton</a>. As with other leptons, the muon is not thought to be composed of any simpler particles. </p><p>The muon is an unstable <a href="/wiki/Subatomic_particle" title="Subatomic particle">subatomic particle</a> with a <a href="/wiki/Mean_lifetime" class="mw-redirect" title="Mean lifetime">mean lifetime</a> of <span class="nowrap"><span data-sort-value="6994220000000000000♠"></span>2.2 <a href="/wiki/Microsecond" title="Microsecond">μs</a></span>, much longer than many other subatomic particles. As with the decay of the free <a href="/wiki/Neutron" title="Neutron">neutron</a> (with a lifetime around 15 minutes), muon decay is slow (by subatomic standards) because the decay is mediated only by the <a href="/wiki/Weak_interaction" title="Weak interaction">weak interaction</a> (rather than the more powerful <a href="/wiki/Strong_interaction" title="Strong interaction">strong interaction</a> or <a href="/wiki/Electromagnetic_interaction" class="mw-redirect" title="Electromagnetic interaction">electromagnetic interaction</a>), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic <a href="/wiki/Degrees_of_freedom" title="Degrees of freedom">degrees of freedom</a> for decay. Muon decay almost always produces at least three particles, which must include an electron of the same charge as the muon and two types of <a href="/wiki/Neutrino" title="Neutrino">neutrinos</a>. </p><p>Like all elementary particles, the muon has a corresponding <a href="/wiki/Antiparticle" title="Antiparticle">antiparticle</a> of opposite charge (+1 <i>e</i>) but equal <a href="/wiki/Mass" title="Mass">mass</a> and spin: the <b>antimuon</b> (also called a <i>positive muon</i>). Muons are denoted by <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> and antimuons by <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">+</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span>. Formerly, muons were called <i>mu mesons</i>, but are not classified as <a href="/wiki/Meson" title="Meson">mesons</a> by modern particle physicists <style data-mw-deduplicate="TemplateStyles:r1033199720">.mw-parser-output div.crossreference{padding-left:0}</style><style data-mw-deduplicate="TemplateStyles:r1236090951">.mw-parser-output .hatnote{font-style:italic}.mw-parser-output div.hatnote{padding-left:1.6em;margin-bottom:0.5em}.mw-parser-output .hatnote i{font-style:normal}.mw-parser-output .hatnote+link+.hatnote{margin-top:-0.5em}@media print{body.ns-0 .mw-parser-output .hatnote{display:none!important}}</style><span role="note" class="hatnote navigation-not-searchable crossreference selfref">(see <a href="#History">§ History</a>)</span>, and that name is no longer used by the physics community. </p><p>Muons have a <a href="/wiki/Mass" title="Mass">mass</a> of <span class="nowrap"><span data-sort-value="7002105660000000000♠"></span>105.66 <span class="nowrap"><a href="/wiki/Electronvolt#Mass" title="Electronvolt">MeV/<i>c</i><sup>2</sup></a></span></span>, which is approximately <span class="nowrap"><span data-sort-value="7002206768282700000♠"></span>206.768<span style="margin-left:.25em;">2827</span>(46)</span><span style="visibility:hidden; color:transparent; padding-left:2px">‍</span><sup id="cite_ref-physconst-mmuome_6-0" class="reference"><a href="#cite_note-physconst-mmuome-6"><span class="cite-bracket">[</span>6<span class="cite-bracket">]</span></a></sup> times that of the electron, <i>m</i><sub>e</sub>. There is also a third lepton, the <a href="/wiki/Tau_(particle)" title="Tau (particle)">tau</a>, approximately 17 times heavier than the muon. </p><p>Due to their greater mass, muons accelerate more slowly than electrons in electromagnetic fields, and emit less <a href="/wiki/Bremsstrahlung" title="Bremsstrahlung">bremsstrahlung</a> (deceleration radiation). This allows muons of a given energy to <a href="/wiki/Stopping_power_(particle_radiation)" title="Stopping power (particle radiation)">penetrate far deeper</a> into matter because the deceleration of electrons and muons is primarily due to energy loss by the bremsstrahlung mechanism. For example, so-called secondary muons, created by <a href="/wiki/Cosmic_rays" class="mw-redirect" title="Cosmic rays">cosmic rays</a> hitting the atmosphere, can penetrate the atmosphere and reach Earth's land surface and even into deep mines. </p><p>Because muons have a greater mass and energy than the <a href="/wiki/Decay_energy" title="Decay energy">decay energy</a> of radioactivity, they are not produced by <a href="/wiki/Radioactive_decay" title="Radioactive decay">radioactive decay</a>. Nonetheless, they are produced in great amounts in high-energy interactions in normal matter, in certain <a href="/wiki/Particle_accelerator" title="Particle accelerator">particle accelerator</a> experiments with <a href="/wiki/Hadron" title="Hadron">hadrons</a>, and in cosmic ray interactions with matter. These interactions usually produce <a href="/wiki/Pi_meson" class="mw-redirect" title="Pi meson">pi mesons</a> initially, which almost always decay to muons. </p><p>As with the other charged leptons, the muon has an associated <a href="/wiki/Muon_neutrino" title="Muon neutrino">muon neutrino</a>, denoted by <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>ν<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">μ</sub></span></span></span>, which differs from the <a href="/wiki/Electron_neutrino" title="Electron neutrino">electron neutrino</a> and participates in different nuclear reactions. </p> <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="History_of_Discovery">History of Discovery</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=1" title="Edit section: History of Discovery"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Muons were discovered by <a href="/wiki/Carl_D._Anderson" class="mw-redirect" title="Carl D. Anderson">Carl D. Anderson</a> and <a href="/wiki/Seth_Neddermeyer" title="Seth Neddermeyer">Seth Neddermeyer</a> at <a href="/wiki/California_Institute_of_Technology" title="California Institute of Technology">Caltech</a> in 1936 while studying <a href="/wiki/Cosmic_radiation" class="mw-redirect" title="Cosmic radiation">cosmic radiation</a>. Anderson noticed particles that curved differently from electrons and other known particles when passed through a <a href="/wiki/Magnetic_field" title="Magnetic field">magnetic field</a>. They were negatively charged but curved less sharply than electrons, but more sharply than <a href="/wiki/Proton" title="Proton">protons</a>, for particles of the same velocity. It was assumed that the magnitude of their negative electric charge was equal to that of the electron, and so to account for the difference in curvature, it was supposed that their mass was greater than an electron's but smaller than a proton's. Thus Anderson initially called the new particle a <i>mesotron</i>, adopting the prefix <i>meso-</i> from the Greek word for "mid-". The existence of the muon was confirmed in 1937 by <a href="/wiki/J._Curry_Street" title="J. Curry Street">J. C. Street</a> and E. C. Stevenson's <a href="/wiki/Cloud_chamber" title="Cloud chamber">cloud chamber</a> experiment.<sup id="cite_ref-7" class="reference"><a href="#cite_note-7"><span class="cite-bracket">[</span>7<span class="cite-bracket">]</span></a></sup> </p><p>A particle with a mass in the <a href="/wiki/Meson" title="Meson">meson</a> range had been predicted before the discovery of any mesons, by theorist <a href="/wiki/Hideki_Yukawa" title="Hideki Yukawa">Hideki Yukawa</a>:<sup id="cite_ref-8" class="reference"><a href="#cite_note-8"><span class="cite-bracket">[</span>8<span class="cite-bracket">]</span></a></sup> </p> <blockquote> <p>It seems natural to modify the theory of Heisenberg and Fermi in the following way. The transition of a heavy particle from neutron state to proton state is not always accompanied by the emission of light particles. The transition is sometimes taken up by another heavy particle. </p> </blockquote> <p>Because of its mass, the mu meson was initially thought to be Yukawa's particle and some scientists, including <a href="/wiki/Niels_Bohr" title="Niels Bohr">Niels Bohr</a>, originally named it the <i>yukon</i>. The fact that the mesotron (i.e. the muon) was not Yukawa's particle was established in 1946 by an experiment conducted by <a href="/wiki/Marcello_Conversi" title="Marcello Conversi">Marcello Conversi</a>, <a href="/wiki/Oreste_Piccioni" title="Oreste Piccioni">Oreste Piccioni</a>, and Ettore Pancini in Rome. In this experiment, which <a href="/wiki/Luis_Walter_Alvarez" title="Luis Walter Alvarez">Luis Walter Alvarez</a> called the "start of modern particle physics" in his 1968 Nobel lecture,<sup id="cite_ref-Nobel_9-0" class="reference"><a href="#cite_note-Nobel-9"><span class="cite-bracket">[</span>9<span class="cite-bracket">]</span></a></sup> they showed that the muons from cosmic rays were decaying without being captured by atomic nuclei, contrary to what was expected of the mediator of the <a href="/wiki/Nuclear_force" title="Nuclear force">nuclear force</a> postulated by Yukawa. Yukawa's predicted particle, the <a href="/wiki/Pi_meson" class="mw-redirect" title="Pi meson">pi meson</a>, was finally identified in 1947 (again from cosmic ray interactions). </p><p>With two particles now known with the intermediate mass, the more general term <i>meson</i> was adopted to refer to any such particle within the correct mass range between electrons and nucleons. Further, in order to differentiate between the two different types of mesons after the second meson was discovered, the initial mesotron particle was renamed the <i>mu meson</i> (the Greek letter <i>μ</i> [<i>mu</i>] corresponds to <i>m</i>), and the new 1947 meson (Yukawa's particle) was named the <i>pi meson</i>. </p><p>As more types of mesons were discovered in accelerator experiments later, it was eventually found that the mu meson significantly differed not only from the pi meson (of about the same mass), but also from all other types of mesons. The difference, in part, was that mu mesons did not interact with the nuclear force, as pi mesons did (and were required to do, in Yukawa's theory). Newer mesons also showed evidence of behaving like the pi meson in nuclear interactions, but not like the mu meson. Also, the mu meson's decay products included both a <a href="/wiki/Neutrino" title="Neutrino">neutrino</a> and an <a href="/wiki/Antineutrino" class="mw-redirect" title="Antineutrino">antineutrino</a>, rather than just one or the other, as was observed in the decay of other charged mesons. </p><p>In the eventual <a href="/wiki/Standard_Model" title="Standard Model">Standard Model</a> of <a href="/wiki/Particle_physics" title="Particle physics">particle physics</a> codified in the 1970s, all mesons other than the mu meson were understood to be <a href="/wiki/Hadrons" class="mw-redirect" title="Hadrons">hadrons</a> – that is, particles made of <a href="/wiki/Quarks" class="mw-redirect" title="Quarks">quarks</a> – and thus subject to the nuclear force. In the quark model, a <i>meson</i> was no longer defined by mass (for some had been discovered that were very massive – more than <a href="/wiki/Nucleon" title="Nucleon">nucleons</a>), but instead were particles composed of exactly two quarks (a quark and antiquark), unlike the <a href="/wiki/Baryon" title="Baryon">baryons</a>, which are defined as particles composed of three quarks (protons and neutrons were the lightest baryons). Mu mesons, however, had shown themselves to be fundamental particles (leptons) like electrons, with no quark structure. Thus, mu "mesons" were not mesons at all, in the new sense and use of the term <i>meson</i> used with the quark model of particle structure. </p><p>With this change in definition, the term <i>mu meson</i> was abandoned, and replaced whenever possible with the modern term <i>muon</i>, making the term "mu meson" only a historical footnote. In the new quark model, other types of mesons sometimes continued to be referred to in shorter terminology (e.g., <i>pion</i> for pi meson), but in the case of the muon, it retained the shorter name and was never again properly referred to by older "mu meson" terminology. </p><p>The eventual recognition of the muon as a simple "heavy electron", with no role at all in the nuclear interaction, seemed so incongruous and surprising at the time, that Nobel laureate <a href="/wiki/Isidor_Isaac_Rabi" title="Isidor Isaac Rabi">I. I. Rabi</a> famously quipped, "Who ordered that?"<sup id="cite_ref-Bartusiak_10-0" class="reference"><a href="#cite_note-Bartusiak-10"><span class="cite-bracket">[</span>10<span class="cite-bracket">]</span></a></sup> </p><p>In the <a href="/wiki/Experimental_testing_of_time_dilation#Rossi–Hall_experiment" title="Experimental testing of time dilation">Rossi–Hall experiment</a> (1941), muons were used to observe the <a href="/wiki/Time_dilation" title="Time dilation">time dilation</a> (or, alternatively, <a href="/wiki/Length_contraction" title="Length contraction">length contraction</a>) predicted by <a href="/wiki/Special_relativity" title="Special relativity">special relativity</a>, for the first time.<sup id="cite_ref-11" class="reference"><a href="#cite_note-11"><span class="cite-bracket">[</span>11<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Muon_sources">Muon sources</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=2" title="Edit section: Muon sources"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Hard-component-muon-868x1024.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Hard-component-muon-868x1024.png/220px-Hard-component-muon-868x1024.png" decoding="async" width="220" height="260" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Hard-component-muon-868x1024.png/330px-Hard-component-muon-868x1024.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Hard-component-muon-868x1024.png/440px-Hard-component-muon-868x1024.png 2x" data-file-width="868" data-file-height="1024" /></a><figcaption>Cosmic ray muon passing through lead in cloud chamber</figcaption></figure> <p>Muons arriving on the Earth's surface are created indirectly as decay products of collisions of cosmic rays with particles of the Earth's atmosphere.<sup id="cite_ref-12" class="reference"><a href="#cite_note-12"><span class="cite-bracket">[</span>12<span class="cite-bracket">]</span></a></sup> </p> <style data-mw-deduplicate="TemplateStyles:r1244412712">.mw-parser-output .templatequote{overflow:hidden;margin:1em 0;padding:0 32px}.mw-parser-output .templatequotecite{line-height:1.5em;text-align:left;margin-top:0}@media(min-width:500px){.mw-parser-output .templatequotecite{padding-left:1.6em}}</style><blockquote class="templatequote"><p>About 10,000 muons reach every square meter of the earth's surface a minute; these charged particles form as by-products of cosmic rays colliding with molecules in the upper atmosphere. Traveling at relativistic speeds, muons can penetrate tens of meters into rocks and other matter before attenuating as a result of absorption or deflection by other atoms.<sup id="cite_ref-13" class="reference"><a href="#cite_note-13"><span class="cite-bracket">[</span>13<span class="cite-bracket">]</span></a></sup></p></blockquote> <p>When a cosmic ray proton impacts atomic nuclei in the upper atmosphere, <a href="/wiki/Pion" title="Pion">pions</a> are created. These decay within a relatively short distance (meters) into muons (their preferred decay product), and <a href="/wiki/Muon_neutrino" title="Muon neutrino">muon neutrinos</a>. The muons from these high-energy cosmic rays generally continue in about the same direction as the original proton, at a velocity near the <a href="/wiki/Speed_of_light" title="Speed of light">speed of light</a>. Although their lifetime <i>without</i> relativistic effects would allow a half-survival distance of only about 456 meters <span class="nowrap">( 2.197 μs × ln(2) × 0.9997 × <span class="texhtml mvar" style="font-style:italic;">c</span> )</span> at most (as seen from Earth), the <a href="/wiki/Time_dilation" title="Time dilation">time dilation</a> effect of <a href="/wiki/Special_relativity" title="Special relativity">special relativity</a> (from the viewpoint of the Earth) allows cosmic ray secondary muons to survive the flight to the Earth's surface, since in the Earth frame the muons have a longer <a href="/wiki/Half-life" title="Half-life">half-life</a> due to their velocity. From the viewpoint (<a href="/wiki/Inertial_frame" class="mw-redirect" title="Inertial frame">inertial frame</a>) of the muon, on the other hand, it is the <a href="/wiki/Length_contraction" title="Length contraction">length contraction</a> effect of special relativity that allows this penetration, since in the muon frame its lifetime is unaffected, but the length contraction causes distances through the atmosphere and Earth to be far shorter than these distances in the Earth rest-frame. Both effects are equally valid ways of explaining the fast muon's unusual survival over distances. </p><p>Since muons are unusually penetrative of ordinary matter, like neutrinos, they are also detectable deep underground (700 meters at the <a href="/wiki/Soudan_2" title="Soudan 2">Soudan 2</a> detector) and underwater, where they form a major part of the natural background ionizing radiation. Like cosmic rays, as noted, this secondary muon radiation is also directional. </p><p>The same nuclear reaction described above (i.e. hadron–hadron impacts to produce pion beams, which then quickly decay to muon beams over short distances) is used by particle physicists to produce muon beams, such as the beam used for the muon <a href="/wiki/Muon_g-2" title="Muon g-2"><i>g</i>−2 experiment</a>.<sup id="cite_ref-14" class="reference"><a href="#cite_note-14"><span class="cite-bracket">[</span>14<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Muon_decay">Muon decay</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=3" title="Edit section: Muon decay"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <figure class="mw-default-size mw-halign-right" typeof="mw:File/Thumb"><a href="/wiki/File:Muon_Decay.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/1/13/Muon_Decay.svg/220px-Muon_Decay.svg.png" decoding="async" width="220" height="193" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/1/13/Muon_Decay.svg/330px-Muon_Decay.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/1/13/Muon_Decay.svg/440px-Muon_Decay.svg.png 2x" data-file-width="400" data-file-height="350" /></a><figcaption>The most common decay of the muon</figcaption></figure> <p>Muons are unstable elementary particles and are heavier than electrons and neutrinos but lighter than all other matter particles. They decay via the <a href="/wiki/Weak_interaction" title="Weak interaction">weak interaction</a>. Because <a href="/wiki/Lepton_number" title="Lepton number">leptonic family numbers</a> are conserved in the absence of an extremely unlikely immediate <a href="/wiki/Neutrino_oscillation" title="Neutrino oscillation">neutrino oscillation</a>, one of the product neutrinos of muon decay must be a muon-type neutrino and the other an electron-type antineutrino (antimuon decay produces the corresponding antiparticles, as detailed below). </p><p>Because charge must be conserved, one of the products of muon decay is always an electron of the same charge as the muon (a positron if it is a positive muon). Thus all muons decay to at least an electron, and two neutrinos. Sometimes, besides these necessary products, additional other particles that have no net charge and spin of zero (e.g., a pair of photons, or an electron-positron pair), are produced. </p><p>The dominant muon decay mode (sometimes called the Michel decay after <a href="/wiki/Louis_Michel_(physicist)" title="Louis Michel (physicist)">Louis Michel</a>) is the simplest possible: the muon decays to an electron, an electron antineutrino, and a muon neutrino. Antimuons, in mirror fashion, most often decay to the corresponding antiparticles: a <a href="/wiki/Positron" title="Positron">positron</a>, an electron neutrino, and a muon antineutrino. In formulaic terms, these two decays are: </p> <dl><dd><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> → <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + <span class="texhtml"><span style="white-space:nowrap;"><a href="/wiki/Electron_antineutrino" class="mw-redirect" title="Electron antineutrino"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span><span style="text-decoration:overline;">ν</span><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">e</sub></span></span></a></span> + <span style="white-space:nowrap;"><a href="/wiki/Muon_neutrino" title="Muon neutrino"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>ν<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">μ</sub></span></span></a></span></span></dd> <dd><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">+</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> → <span style="white-space:nowrap;"><a href="/wiki/Positron" title="Positron"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">+</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></a></span> + <span class="texhtml"><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>ν<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">e</sub></span></span></span> + <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span><span style="text-decoration:overline;">ν</span><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:-0.4em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline">μ</sub></span></span></span></span></dd></dl> <p>The mean lifetime, <span class="texhtml"><var style="padding-right: 1px;">τ</var> = <var style="padding-right: 1px;">ħ</var>/<var style="padding-right: 1px;">Γ</var></span>, of the (positive) muon is <span class="nowrap"><span data-sort-value="6994219698110000000♠"></span>2.196<span style="margin-left:.25em;">9811</span><span style="margin-left:0.3em;margin-right:0.15em;">±</span>0.000<span style="margin-left:.25em;">0022</span> <a href="/wiki/Microsecond" title="Microsecond">μs</a></span>.<sup id="cite_ref-PDG2012_4-1" class="reference"><a href="#cite_note-PDG2012-4"><span class="cite-bracket">[</span>4<span class="cite-bracket">]</span></a></sup> The equality of the muon and antimuon lifetimes has been established to better than one part in 10<sup>4</sup>.<sup id="cite_ref-ChargeRatio_15-0" class="reference"><a href="#cite_note-ChargeRatio-15"><span class="cite-bracket">[</span>15<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Prohibited_decays">Prohibited decays</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=4" title="Edit section: Prohibited decays"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>Certain neutrino-less decay modes are kinematically allowed but are, for all practical purposes, forbidden in the <a href="/wiki/Standard_Model" title="Standard Model">Standard Model</a>, even given that neutrinos have mass and oscillate. Examples forbidden by lepton flavour conservation are: </p> <dl><dd><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> → <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>γ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span></dd></dl> <p>and </p> <dl><dd><span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> → <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">+</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> .</dd></dl> <p>Taking into account neutrino mass, a decay like <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> → <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">−</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>γ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> is technically possible in the Standard Model (for example by <a href="/wiki/Neutrino_oscillation" title="Neutrino oscillation">neutrino oscillation</a> of a virtual muon neutrino into an electron neutrino), but such a decay is extremely unlikely and therefore should be experimentally unobservable. Fewer than one in 10<sup>50</sup> muon decays should produce such a decay. </p><p>Observation of such decay modes would constitute clear evidence for theories <a href="/wiki/Beyond_the_Standard_Model" class="mw-redirect" title="Beyond the Standard Model">beyond the Standard Model</a>. Upper limits for the branching fractions of such decay modes were measured in many experiments starting more than 60 years ago. The current upper limit for the <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>μ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">+</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> → <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>e<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline">+</sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> + <span style="white-space:nowrap;"><span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:right"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span>γ<span class="nowrap"><span style="display:inline-block;margin-bottom:-0.3em;vertical-align:0.8em;line-height:1.0em;font-size:80%;text-align:left"><sup style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sup><br /><sub style="font-size:inherit;line-height:inherit;vertical-align:baseline"></sub></span></span></span> branching fraction was measured 2009–2013 in the <a href="/wiki/Mu_to_E_Gamma" title="Mu to E Gamma">MEG</a> experiment and is <span class="nowrap"><span data-sort-value="6987420000000000000♠"></span>4.2<span style="margin-left:0.25em;margin-right:0.15em;">×</span>10<sup>−13</sup></span>.<sup id="cite_ref-Baldini_16-0" class="reference"><a href="#cite_note-Baldini-16"><span class="cite-bracket">[</span>16<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Theoretical_decay_rate">Theoretical decay rate</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=5" title="Edit section: Theoretical decay rate"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">See also: <a href="/wiki/Michel_parameters" title="Michel parameters">Michel parameters</a></div> <style data-mw-deduplicate="TemplateStyles:r1251242444">.mw-parser-output .ambox{border:1px solid #a2a9b1;border-left:10px solid #36c;background-color:#fbfbfb;box-sizing:border-box}.mw-parser-output .ambox+link+.ambox,.mw-parser-output .ambox+link+style+.ambox,.mw-parser-output .ambox+link+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+style+.ambox,.mw-parser-output .ambox+.mw-empty-elt+link+link+.ambox{margin-top:-1px}html body.mediawiki .mw-parser-output .ambox.mbox-small-left{margin:4px 1em 4px 0;overflow:hidden;width:238px;border-collapse:collapse;font-size:88%;line-height:1.25em}.mw-parser-output .ambox-speedy{border-left:10px solid #b32424;background-color:#fee7e6}.mw-parser-output .ambox-delete{border-left:10px solid #b32424}.mw-parser-output .ambox-content{border-left:10px solid #f28500}.mw-parser-output .ambox-style{border-left:10px solid #fc3}.mw-parser-output .ambox-move{border-left:10px solid #9932cc}.mw-parser-output .ambox-protection{border-left:10px solid #a2a9b1}.mw-parser-output .ambox .mbox-text{border:none;padding:0.25em 0.5em;width:100%}.mw-parser-output .ambox .mbox-image{border:none;padding:2px 0 2px 0.5em;text-align:center}.mw-parser-output .ambox .mbox-imageright{border:none;padding:2px 0.5em 2px 0;text-align:center}.mw-parser-output .ambox .mbox-empty-cell{border:none;padding:0;width:1px}.mw-parser-output .ambox .mbox-image-div{width:52px}@media(min-width:720px){.mw-parser-output .ambox{margin:0 10%}}@media print{body.ns-0 .mw-parser-output .ambox{display:none!important}}</style><table class="box-More_citations_needed_section plainlinks metadata ambox ambox-content ambox-Refimprove" role="presentation"><tbody><tr><td class="mbox-image"><div class="mbox-image-div"><span typeof="mw:File"><a href="/wiki/File:Question_book-new.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/50px-Question_book-new.svg.png" decoding="async" width="50" height="39" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/75px-Question_book-new.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/9/99/Question_book-new.svg/100px-Question_book-new.svg.png 2x" data-file-width="512" data-file-height="399" /></a></span></div></td><td class="mbox-text"><div class="mbox-text-span">This section <b>needs additional citations for <a href="/wiki/Wikipedia:Verifiability" title="Wikipedia:Verifiability">verification</a></b>.<span class="hide-when-compact"> Please help <a href="/wiki/Special:EditPage/Muon" title="Special:EditPage/Muon">improve this article</a> by <a href="/wiki/Help:Referencing_for_beginners" title="Help:Referencing for beginners">adding citations to reliable sources</a> in this section. Unsourced material may be challenged and removed.</span> <span class="date-container"><i>(<span class="date">June 2021</span>)</i></span><span class="hide-when-compact"><i> (<small><a href="/wiki/Help:Maintenance_template_removal" title="Help:Maintenance template removal">Learn how and when to remove this message</a></small>)</i></span></div></td></tr></tbody></table> <p>The muon <a href="/wiki/Decay_width" class="mw-redirect" title="Decay width">decay width</a> that follows from <a href="/wiki/Fermi%27s_golden_rule" title="Fermi's golden rule">Fermi's golden rule</a> has dimension of energy, and must be proportional to the square of the amplitude, and thus the square of <a href="/wiki/Fermi_constant" class="mw-redirect" title="Fermi constant">Fermi's coupling constant</a> (<span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle G_{\text{F}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>G</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>F</mtext> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle G_{\text{F}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/463ea1548afad99674dbb1436b7d611525bb1cb2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.132ex; height:2.509ex;" alt="{\displaystyle G_{\text{F}}}" /></span>), with over-all dimension of inverse fourth power of energy. By dimensional analysis, this leads to <a href="/wiki/Q_value_(nuclear_science)#Applications" title="Q value (nuclear science)">Sargent's rule</a> of fifth-power dependence on <span class="texhtml"><i>m</i><sub><i>μ</i></sub></span>,<sup id="cite_ref-17" class="reference"><a href="#cite_note-17"><span class="cite-bracket">[</span>17<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-DecayFormula_18-0" class="reference"><a href="#cite_note-DecayFormula-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \Gamma ={\frac {G_{\text{F}}^{2}m_{\mu }^{5}}{192\pi ^{3}}}~I\left({\frac {m_{\text{e}}^{2}}{m_{\mu }^{2}}}\right),}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi mathvariant="normal">Γ</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msubsup> <mi>G</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>F</mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msubsup> <msubsup> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>5</mn> </mrow> </msubsup> </mrow> <mrow> <mn>192</mn> <msup> <mi>π</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> </msup> </mrow> </mfrac> </mrow> <mtext> </mtext> <mi>I</mi> <mrow> <mo>(</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <msubsup> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>e</mtext> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msubsup> <msubsup> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msubsup> </mfrac> </mrow> <mo>)</mo> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \Gamma ={\frac {G_{\text{F}}^{2}m_{\mu }^{5}}{192\pi ^{3}}}~I\left({\frac {m_{\text{e}}^{2}}{m_{\mu }^{2}}}\right),}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/d60229addd5d4ee1780522bf20b250a76f94e446" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -3.171ex; width:22.738ex; height:7.509ex;" alt="{\displaystyle \Gamma ={\frac {G_{\text{F}}^{2}m_{\mu }^{5}}{192\pi ^{3}}}~I\left({\frac {m_{\text{e}}^{2}}{m_{\mu }^{2}}}\right),}" /></span></dd></dl> <p>where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle I(x)=1-8x-12x^{2}\ln x+8x^{3}-x^{4}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>I</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mn>1</mn> <mo>−</mo> <mn>8</mn> <mi>x</mi> <mo>−</mo> <mn>12</mn> <msup> <mi>x</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mi>ln</mi> <mo>⁡</mo> <mi>x</mi> <mo>+</mo> <mn>8</mn> <msup> <mi>x</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> </msup> <mo>−</mo> <msup> <mi>x</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>4</mn> </mrow> </msup> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle I(x)=1-8x-12x^{2}\ln x+8x^{3}-x^{4}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/0201dfae4373866c2beecebc059f636cbba14754" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:37.108ex; height:3.176ex;" alt="{\displaystyle I(x)=1-8x-12x^{2}\ln x+8x^{3}-x^{4}}" /></span>,<sup id="cite_ref-DecayFormula_18-1" class="reference"><a href="#cite_note-DecayFormula-18"><span class="cite-bracket">[</span>18<span class="cite-bracket">]</span></a></sup> and: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle x={\frac {2\,E_{\text{e}}}{m_{\mu }\,c^{2}}}}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>x</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mn>2</mn> <mspace width="thinmathspace"></mspace> <msub> <mi>E</mi> <mrow class="MJX-TeXAtom-ORD"> <mtext>e</mtext> </mrow> </msub> </mrow> <mrow> <msub> <mi>m</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> </msub> <mspace width="thinmathspace"></mspace> <msup> <mi>c</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> </mrow> </mfrac> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle x={\frac {2\,E_{\text{e}}}{m_{\mu }\,c^{2}}}}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2ee597b5b80540bd95b573e4486db58c22464706" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.838ex; width:10.976ex; height:6.176ex;" alt="{\displaystyle x={\frac {2\,E_{\text{e}}}{m_{\mu }\,c^{2}}}}" /></span> is the fraction of the maximum energy transmitted to the electron.</dd></dl> <p>The decay distributions of the electron in muon decays have been parameterised using the so-called Michel parameters. The values of these four parameters are predicted unambiguously in the Standard Model of particle physics, thus muon decays represent a good test of the spacetime structure of the <a href="/wiki/Weak_interaction" title="Weak interaction">weak interaction</a>. No deviation from the Standard Model predictions has yet been found. </p><p>For the decay of the muon, the expected decay distribution for the Standard Model values of Michel parameters is </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {\partial ^{2}\Gamma }{\partial x\,\partial {\cos \theta }}}\sim x^{2}[(3-2x)+P_{\mu }\cos \theta \,(1-2x)]}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <msup> <mi mathvariant="normal">∂</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mi mathvariant="normal">Γ</mi> </mrow> <mrow> <mi mathvariant="normal">∂</mi> <mi>x</mi> <mspace width="thinmathspace"></mspace> <mi mathvariant="normal">∂</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>cos</mi> <mo>⁡</mo> <mi>θ</mi> </mrow> </mrow> </mfrac> </mrow> <mo>∼</mo> <msup> <mi>x</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo stretchy="false">[</mo> <mo stretchy="false">(</mo> <mn>3</mn> <mo>−</mo> <mn>2</mn> <mi>x</mi> <mo stretchy="false">)</mo> <mo>+</mo> <msub> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> </msub> <mi>cos</mi> <mo>⁡</mo> <mi>θ</mi> <mspace width="thinmathspace"></mspace> <mo stretchy="false">(</mo> <mn>1</mn> <mo>−</mo> <mn>2</mn> <mi>x</mi> <mo stretchy="false">)</mo> <mo stretchy="false">]</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {\partial ^{2}\Gamma }{\partial x\,\partial {\cos \theta }}}\sim x^{2}[(3-2x)+P_{\mu }\cos \theta \,(1-2x)]}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/69b10f695c3f6544a77d70c1b2850199737cee75" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:44.081ex; height:5.843ex;" alt="{\displaystyle {\frac {\partial ^{2}\Gamma }{\partial x\,\partial {\cos \theta }}}\sim x^{2}[(3-2x)+P_{\mu }\cos \theta \,(1-2x)]}" /></span></dd></dl> <p>where <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \theta }"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>θ</mi> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \theta }</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/6e5ab2664b422d53eb0c7df3b87e1360d75ad9af" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.09ex; height:2.176ex;" alt="{\displaystyle \theta }" /></span> is the angle between the muon's polarization vector <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathbf {P} _{\mu }}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">P</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> </msub> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathbf {P} _{\mu }}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/8baa983e9d32872ef652975af8f7e98f11db015b" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:3.05ex; height:2.843ex;" alt="{\displaystyle \mathbf {P} _{\mu }}" /></span> and the decay-electron momentum vector, and <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P_{\mu }=|\mathbf {P} _{\mu }|}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <msub> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> </msub> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> <msub> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="bold">P</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> </msub> <mrow class="MJX-TeXAtom-ORD"> <mo stretchy="false">|</mo> </mrow> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle P_{\mu }=|\mathbf {P} _{\mu }|}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3bbb8e57eaea71402147fb359f2cbdbe0f310ca5" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.005ex; width:10.158ex; height:3.009ex;" alt="{\displaystyle P_{\mu }=|\mathbf {P} _{\mu }|}" /></span> is the fraction of muons that are forward-polarized. Integrating this expression over electron energy gives the angular distribution of the daughter electrons: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {\mathrm {d} \Gamma }{\mathrm {d} {\cos \theta }}}\sim 1-{\frac {1}{3}}P_{\mu }\cos \theta .}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">d</mi> </mrow> <mi mathvariant="normal">Γ</mi> </mrow> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">d</mi> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>cos</mi> <mo>⁡</mo> <mi>θ</mi> </mrow> </mrow> </mfrac> </mrow> <mo>∼</mo> <mn>1</mn> <mo>−</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mn>1</mn> <mn>3</mn> </mfrac> </mrow> <msub> <mi>P</mi> <mrow class="MJX-TeXAtom-ORD"> <mi>μ</mi> </mrow> </msub> <mi>cos</mi> <mo>⁡</mo> <mi>θ</mi> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {\mathrm {d} \Gamma }{\mathrm {d} {\cos \theta }}}\sim 1-{\frac {1}{3}}P_{\mu }\cos \theta .}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/28744639ad2c23a8ba253beb69f525af46887242" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:24.155ex; height:5.509ex;" alt="{\displaystyle {\frac {\mathrm {d} \Gamma }{\mathrm {d} {\cos \theta }}}\sim 1-{\frac {1}{3}}P_{\mu }\cos \theta .}" /></span></dd></dl> <p>The electron energy distribution integrated over the polar angle (valid for <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle x<1}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>x</mi> <mo><</mo> <mn>1</mn> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle x<1}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3f6c78a35f9b16dabbc40b39d4d1f2571ea5d3db" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:5.591ex; height:2.176ex;" alt="{\displaystyle x<1}" /></span>) is </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\frac {\mathrm {d} \Gamma }{\mathrm {d} x}}\sim (3x^{2}-2x^{3}).}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">d</mi> </mrow> <mi mathvariant="normal">Γ</mi> </mrow> <mrow> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">d</mi> </mrow> <mi>x</mi> </mrow> </mfrac> </mrow> <mo>∼</mo> <mo stretchy="false">(</mo> <mn>3</mn> <msup> <mi>x</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>2</mn> </mrow> </msup> <mo>−</mo> <mn>2</mn> <msup> <mi>x</mi> <mrow class="MJX-TeXAtom-ORD"> <mn>3</mn> </mrow> </msup> <mo stretchy="false">)</mo> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle {\frac {\mathrm {d} \Gamma }{\mathrm {d} x}}\sim (3x^{2}-2x^{3}).}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/ca9a3d34fff4d47a9d1014ea3fd068212b26634c" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.005ex; width:19.069ex; height:5.509ex;" alt="{\displaystyle {\frac {\mathrm {d} \Gamma }{\mathrm {d} x}}\sim (3x^{2}-2x^{3}).}" /></span></dd></dl> <p>Because the direction the electron is emitted in (a polar vector) is preferentially aligned opposite the muon spin (an <a href="/wiki/Pseudovector" title="Pseudovector">axial vector</a>), the decay is an example of non-conservation of <a href="/wiki/Parity_(physics)" title="Parity (physics)">parity</a> by the weak interaction. This is essentially the same experimental signature as used by the <a href="/wiki/Wu_experiment" title="Wu experiment">original demonstration</a>. More generally in the Standard Model, all charged <a href="/wiki/Lepton" title="Lepton">leptons</a> decay via the weak interaction and likewise violate parity symmetry. </p> <div class="mw-heading mw-heading2"><h2 id="Muonic_atoms">Muonic atoms</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=6" title="Edit section: Muonic atoms"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The muon was the first <a href="/wiki/Elementary_particle" title="Elementary particle">elementary particle</a> discovered that does not appear in ordinary <a href="/wiki/Atom" title="Atom">atoms</a>. </p> <div class="mw-heading mw-heading3"><h3 id="Negative_muon_atoms">Negative muon atoms</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=7" title="Edit section: Negative muon atoms"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><i>Negative</i> muons can form <a href="/wiki/Exotic_atom" title="Exotic atom">muonic atoms</a> (previously called mu-mesic atoms), by replacing an electron in ordinary atoms. Muonic hydrogen atoms are much smaller than typical hydrogen atoms because the much larger mass of the muon gives it a much more localized <a href="/wiki/Ground_state" title="Ground state">ground-state</a> <a href="/wiki/Wavefunction" class="mw-redirect" title="Wavefunction">wavefunction</a> than is observed for the electron. In multi-electron atoms, when only one of the electrons is replaced by a muon, the size of the atom continues to be determined by the other electrons, and the atomic size is nearly unchanged. Nonetheless, in such cases, the orbital of the muon continues to be smaller and far closer to the nucleus than the <a href="/wiki/Atomic_orbital" title="Atomic orbital">atomic orbitals</a> of the electrons. </p><p>Spectroscopic measurements in <a href="/wiki/Muonic_hydrogen" class="mw-redirect" title="Muonic hydrogen">muonic hydrogen</a> have been used to produce a precise estimate of the <a href="/wiki/Proton_radius" class="mw-redirect" title="Proton radius">proton radius</a>.<sup id="cite_ref-Chargeradius_19-0" class="reference"><a href="#cite_note-Chargeradius-19"><span class="cite-bracket">[</span>19<span class="cite-bracket">]</span></a></sup> The results of these measurements diverged from the then accepted value giving rise to the so called <a href="/wiki/Proton_radius_puzzle" title="Proton radius puzzle">proton radius puzzle</a>. Later this puzzle found its resolution when new improved measurements of the proton radius in the electronic hydrogen became available.<sup id="cite_ref-KarrMarchand2019_20-0" class="reference"><a href="#cite_note-KarrMarchand2019-20"><span class="cite-bracket">[</span>20<span class="cite-bracket">]</span></a></sup> </p><p>Muonic <a href="/wiki/Helium" title="Helium">helium</a> is created by substituting a muon for one of the electrons in helium-4. The muon orbits much closer to the nucleus, so muonic helium can therefore be regarded like an isotope of helium whose nucleus consists of two neutrons, two protons and a muon, with a single electron outside. Chemically, muonic helium, possessing an unpaired <a href="/wiki/Valence_electron" title="Valence electron">valence electron</a>, can <a href="/wiki/Chemical_bond" title="Chemical bond">bond</a> with other atoms, and behaves more like a hydrogen atom than an inert helium atom.<sup id="cite_ref-21" class="reference"><a href="#cite_note-21"><span class="cite-bracket">[</span>21<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-22" class="reference"><a href="#cite_note-22"><span class="cite-bracket">[</span>22<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-23" class="reference"><a href="#cite_note-23"><span class="cite-bracket">[</span>23<span class="cite-bracket">]</span></a></sup> </p><p>Muonic heavy hydrogen atoms with a negative muon may undergo nuclear fusion in the process of <a href="/wiki/Muon-catalyzed_fusion" title="Muon-catalyzed fusion">muon-catalyzed fusion</a>, after the muon may leave the new atom to induce fusion in another hydrogen molecule. This process continues until the negative muon is captured by a helium nucleus, where it remains until it decays. </p><p>Negative muons bound to conventional atoms can be captured (<a href="/wiki/Muon_capture" title="Muon capture">muon capture</a>) through the <a href="/wiki/Weak_interaction" title="Weak interaction">weak force</a> by protons in nuclei, in a sort of electron-capture-like process. When this happens, <a href="/wiki/Nuclear_transmutation" title="Nuclear transmutation">nuclear transmutation</a> results: The proton becomes a neutron and a muon neutrino is emitted. </p> <div class="mw-heading mw-heading3"><h3 id="Positive_muon_atoms">Positive muon atoms</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=8" title="Edit section: Positive muon atoms"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>A <i>positive</i> muon, when stopped in ordinary matter, cannot be captured by a proton since the two positive charges can only repel. The positive muon is also not attracted to the nucleus of atoms. Instead, it binds a random electron and with this electron forms an exotic atom known as <a href="/wiki/Muonium" title="Muonium">muonium</a> (mu) atom. In this atom, the muon acts as the nucleus. The positive muon, in this context, can be considered a pseudo-isotope of hydrogen with one ninth of the mass of the proton. Because the mass of the electron is much smaller than the mass of both the proton and the muon, the <a href="/wiki/Reduced_mass" title="Reduced mass">reduced mass</a> of muonium, and hence its <a href="/wiki/Bohr_radius" title="Bohr radius">Bohr radius</a>, is very close to that of <a href="/wiki/Hydrogen" title="Hydrogen">hydrogen</a>. Therefore this bound muon-electron pair can be treated to a first approximation as a short-lived "atom" that behaves chemically like the isotopes of hydrogen (<a href="/wiki/Hydrogen-1" class="mw-redirect" title="Hydrogen-1">protium</a>, <a href="/wiki/Deuterium" title="Deuterium">deuterium</a> and <a href="/wiki/Tritium" title="Tritium">tritium</a>). </p><p>Both positive and negative muons can be part of a short-lived pi-mu atom consisting of a muon and an oppositely charged pion. These atoms were observed in the 1970s in experiments at <a href="/wiki/Brookhaven_National_Laboratory" title="Brookhaven National Laboratory">Brookhaven National Laboratory</a> and <a href="/wiki/Fermilab" title="Fermilab">Fermilab</a>.<sup id="cite_ref-24" class="reference"><a href="#cite_note-24"><span class="cite-bracket">[</span>24<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-25" class="reference"><a href="#cite_note-25"><span class="cite-bracket">[</span>25<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Anomalous_magnetic_dipole_moment">Anomalous magnetic dipole moment</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=9" title="Edit section: Anomalous magnetic dipole moment"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The <a href="/wiki/Anomalous_magnetic_dipole_moment" title="Anomalous magnetic dipole moment">anomalous magnetic dipole moment</a> is the difference between the experimentally observed value of the magnetic dipole moment and the theoretical value predicted by the <a href="/wiki/Dirac_equation" title="Dirac equation">Dirac equation</a>. The measurement and prediction of this value is very important in the <a href="/wiki/Precision_tests_of_QED" title="Precision tests of QED">precision tests of QED</a>. The E821 experiment<sup id="cite_ref-26" class="reference"><a href="#cite_note-26"><span class="cite-bracket">[</span>26<span class="cite-bracket">]</span></a></sup> at Brookhaven and the <a href="/wiki/Muon_g-2" title="Muon g-2">Muon g-2</a> experiment at Fermilab studied the precession of the muon spin in a constant external magnetic field as the muons circulated in a confining storage ring. The Muon g-2 collaboration reported <sup id="cite_ref-27" class="reference"><a href="#cite_note-27"><span class="cite-bracket">[</span>27<span class="cite-bracket">]</span></a></sup> in 2021: </p> <dl><dd><span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle a={\frac {g-2}{2}}=0.00116592061(41).}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>a</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mfrac> <mrow> <mi>g</mi> <mo>−</mo> <mn>2</mn> </mrow> <mn>2</mn> </mfrac> </mrow> <mo>=</mo> <mn>0.00116592061</mn> <mo stretchy="false">(</mo> <mn>41</mn> <mo stretchy="false">)</mo> <mo>.</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle a={\frac {g-2}{2}}=0.00116592061(41).}</annotation> </semantics> </math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/3cf30d386f34efcd05246dba381ad1131e8dc8e2" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:32.759ex; height:5.343ex;" alt="{\displaystyle a={\frac {g-2}{2}}=0.00116592061(41).}" /></span></dd></dl> <p>The prediction for the value of the muon anomalous magnetic moment includes three parts: </p> <dl><dd><span class="texhtml mvar" style="font-style:italic;">a</span><sub><i>μ</i></sub><sup>SM</sup> = <span class="texhtml mvar" style="font-style:italic;">a</span><sub><i>μ</i></sub><sup>QED</sup> + <span class="texhtml mvar" style="font-style:italic;">a</span><sub><i>μ</i></sub><sup>EW</sup> + <span class="texhtml mvar" style="font-style:italic;">a</span><sub><i>μ</i></sub><sup>had</sup>.</dd></dl> <p>The difference between the <a href="/wiki/G-factor_(physics)" title="G-factor (physics)"><i>g</i>-factors</a> of the muon and the electron is due to their difference in mass. Because of the muon's larger mass, contributions to the theoretical calculation of its anomalous magnetic dipole moment from <a href="/wiki/Standard_Model" title="Standard Model">Standard Model</a> <a href="/wiki/Weak_interaction" title="Weak interaction">weak interactions</a> and from contributions involving <a href="/wiki/Hadron" title="Hadron">hadrons</a> are important at the current level of precision, whereas these effects are not important for the electron. The muon's anomalous magnetic dipole moment is also sensitive to contributions from new physics <a href="/wiki/Beyond_the_Standard_Model" class="mw-redirect" title="Beyond the Standard Model">beyond the Standard Model</a>, such as <a href="/wiki/Supersymmetry" title="Supersymmetry">supersymmetry</a>. For this reason, the muon's anomalous magnetic moment is normally used as a probe for new physics beyond the Standard Model rather than as a test of <a href="/wiki/Quantum_electrodynamics" title="Quantum electrodynamics">QED</a>.<sup id="cite_ref-28" class="reference"><a href="#cite_note-28"><span class="cite-bracket">[</span>28<span class="cite-bracket">]</span></a></sup> <a href="/wiki/Muon_g%E2%88%922" class="mw-redirect" title="Muon g−2">Muon <i>g</i>−2</a>, a new experiment at Fermilab using the E821 magnet improved the precision of this measurement.<sup id="cite_ref-29" class="reference"><a href="#cite_note-29"><span class="cite-bracket">[</span>29<span class="cite-bracket">]</span></a></sup> </p><p>In 2020 an international team of 170 physicists calculated the most accurate prediction for the theoretical value of the muon's anomalous magnetic moment.<sup id="cite_ref-30" class="reference"><a href="#cite_note-30"><span class="cite-bracket">[</span>30<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-31" class="reference"><a href="#cite_note-31"><span class="cite-bracket">[</span>31<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading3"><h3 id="Muon_g−2"><span id="Muon_g.E2.88.922"></span>Muon g−2</h3><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=10" title="Edit section: Muon g−2"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p><a href="/wiki/Muon_g-2" title="Muon g-2">Muon g-2</a> is a particle physics experiment at Fermilab to measure the anomalous magnetic dipole moment of a muon to a precision of 0.14 ppm,<sup id="cite_ref-32" class="reference"><a href="#cite_note-32"><span class="cite-bracket">[</span>32<span class="cite-bracket">]</span></a></sup><sup id="cite_ref-NYT-20230810_33-0" class="reference"><a href="#cite_note-NYT-20230810-33"><span class="cite-bracket">[</span>33<span class="cite-bracket">]</span></a></sup> which is a sensitive test of the Standard Model.<sup id="cite_ref-34" class="reference"><a href="#cite_note-34"><span class="cite-bracket">[</span>34<span class="cite-bracket">]</span></a></sup> It might also provide evidence of the existence of entirely new particles.<sup id="cite_ref-35" class="reference"><a href="#cite_note-35"><span class="cite-bracket">[</span>35<span class="cite-bracket">]</span></a></sup> </p><p>In 2021, the Muon g−2 Experiment presented their first results of a new experimental average that increased the difference between experiment and theory to 4.2 standard deviations.<sup id="cite_ref-36" class="reference"><a href="#cite_note-36"><span class="cite-bracket">[</span>36<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="Electric_dipole_moment">Electric dipole moment</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=11" title="Edit section: Electric dipole moment"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <p>The current experimental limit on the muon <a href="/wiki/Electric_dipole_moment" title="Electric dipole moment">electric dipole moment</a>, |<i>d</i><sub><i>μ</i></sub>| < 1.9 × 10<sup>−19</sup> e·cm set by the E821 experiment at the Brookhaven, is orders of magnitude above the Standard Model prediction. The observation of a non-zero muon electric dipole moment would provide an additional source of <a href="/wiki/CP_violation" title="CP violation">CP violation</a>. An improvement in sensitivity by two orders of magnitude over the Brookhaven limit is expected from the experiments at Fermilab. </p> <div class="mw-heading mw-heading2"><h2 id="Muon_radiography_and_tomography">Muon radiography and tomography</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=12" title="Edit section: Muon radiography and tomography"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951" /><div role="note" class="hatnote navigation-not-searchable">Main article: <a href="/wiki/Muon_tomography" title="Muon tomography">Muon tomography</a></div> <p>Since muons are much more deeply penetrating than <a href="/wiki/X-ray" title="X-ray">X-rays</a> or <a href="/wiki/Gamma_ray" title="Gamma ray">gamma rays</a>, muon imaging can be used with much thicker material or, with cosmic ray sources, larger objects. One example is commercial muon tomography used to image entire cargo containers to detect shielded <a href="/wiki/Nuclear_material" title="Nuclear material">nuclear material</a>, as well as explosives or other contraband.<sup id="cite_ref-37" class="reference"><a href="#cite_note-37"><span class="cite-bracket">[</span>37<span class="cite-bracket">]</span></a></sup> </p><p>The technique of muon transmission radiography based on cosmic ray sources was first used in the 1950s to measure the depth of the <a href="/wiki/Overburden" title="Overburden">overburden</a> of a tunnel in Australia<sup id="cite_ref-38" class="reference"><a href="#cite_note-38"><span class="cite-bracket">[</span>38<span class="cite-bracket">]</span></a></sup> and in the 1960s to search for possible hidden chambers in the <a href="/wiki/Pyramid_of_Khafre" title="Pyramid of Khafre">Pyramid of Chephren</a> in <a href="/wiki/Giza" title="Giza">Giza</a>.<sup id="cite_ref-39" class="reference"><a href="#cite_note-39"><span class="cite-bracket">[</span>39<span class="cite-bracket">]</span></a></sup> In 2017, the discovery of a large void (with a length of 30 metres minimum) by observation of cosmic-ray muons was reported.<sup id="cite_ref-Discovery_of_a_big_void_in_Khufu's_Pyramid_by_observation_of_cosmic-ray_muons_40-0" class="reference"><a href="#cite_note-Discovery_of_a_big_void_in_Khufu's_Pyramid_by_observation_of_cosmic-ray_muons-40"><span class="cite-bracket">[</span>40<span class="cite-bracket">]</span></a></sup> </p><p>In 2003, the scientists at <a href="/wiki/Los_Alamos_National_Laboratory" title="Los Alamos National Laboratory">Los Alamos National Laboratory</a> developed a new imaging technique: <i>muon scattering tomography</i>. With muon scattering tomography, both incoming and outgoing trajectories for each particle are reconstructed, such as with sealed aluminum <a href="/wiki/Wire_chamber" title="Wire chamber">drift tubes</a>.<sup id="cite_ref-Radiographic_imaging_with_cosmic-ray_muons_41-0" class="reference"><a href="#cite_note-Radiographic_imaging_with_cosmic-ray_muons-41"><span class="cite-bracket">[</span>41<span class="cite-bracket">]</span></a></sup> Since the development of this technique, several companies have started to use it. </p><p>In August 2014, Decision Sciences International Corporation announced it had been awarded a contract by <a href="/wiki/Toshiba" title="Toshiba">Toshiba</a> for use of its muon tracking detectors in reclaiming the <a href="/wiki/Fukushima_Daiichi_Nuclear_Power_Plant" title="Fukushima Daiichi Nuclear Power Plant">Fukushima nuclear complex</a>.<sup id="cite_ref-42" class="reference"><a href="#cite_note-42"><span class="cite-bracket">[</span>42<span class="cite-bracket">]</span></a></sup> The Fukushima Daiichi Tracker was proposed to make a few months of muon measurements to show the distribution of the reactor cores. In December 2014, <a href="/wiki/Tokyo_Electric_Power_Company" title="Tokyo Electric Power Company">Tepco</a> reported that they would be using two different muon imaging techniques at Fukushima, "muon scanning method" on Unit 1 (the most badly damaged, where the fuel may have left the reactor vessel) and "muon scattering method" on Unit 2.<sup id="cite_ref-43" class="reference"><a href="#cite_note-43"><span class="cite-bracket">[</span>43<span class="cite-bracket">]</span></a></sup> The International Research Institute for Nuclear Decommissioning <a href="/w/index.php?title=IRID&action=edit&redlink=1" class="new" title="IRID (page does not exist)">IRID</a> in Japan and the High Energy Accelerator Research Organization <a href="/wiki/KEK" title="KEK">KEK</a> call the method they developed for Unit 1 the "muon permeation method"; 1,200 optical fibers for wavelength conversion light up when muons come into contact with them.<sup id="cite_ref-44" class="reference"><a href="#cite_note-44"><span class="cite-bracket">[</span>44<span class="cite-bracket">]</span></a></sup> After a month of data collection, it is hoped to reveal the location and amount of fuel debris still inside the reactor. The measurements began in February 2015.<sup id="cite_ref-45" class="reference"><a href="#cite_note-45"><span class="cite-bracket">[</span>45<span class="cite-bracket">]</span></a></sup> </p> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=13" title="Edit section: See also"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><a href="/wiki/Comet_(experiment)" title="Comet (experiment)">Comet (experiment)</a>, searching for the elusive coherent neutrino-less conversion of a muon to an electron in J-PARC</li> <li><a href="/wiki/List_of_particles" title="List of particles">List of particles</a></li> <li><a href="/wiki/Mu2e" title="Mu2e">Mu2e</a>, an experiment to detect neutrinoless conversion of muons to electrons</li> <li><a href="/wiki/Muometric_navigation" title="Muometric navigation">Muometric navigation</a></li> <li><a href="/wiki/Muon_spin_spectroscopy" title="Muon spin spectroscopy">Muon spin spectroscopy</a></li> <li><a href="/wiki/Muon_tomography" title="Muon tomography">Muon tomography</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="References">References</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=14" title="Edit section: References"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <style data-mw-deduplicate="TemplateStyles:r1239543626">.mw-parser-output .reflist{margin-bottom:0.5em;list-style-type:decimal}@media screen{.mw-parser-output .reflist{font-size:90%}}.mw-parser-output .reflist .references{font-size:100%;margin-bottom:0;list-style-type:inherit}.mw-parser-output .reflist-columns-2{column-width:30em}.mw-parser-output .reflist-columns-3{column-width:25em}.mw-parser-output .reflist-columns{margin-top:0.3em}.mw-parser-output .reflist-columns ol{margin-top:0}.mw-parser-output .reflist-columns li{page-break-inside:avoid;break-inside:avoid-column}.mw-parser-output .reflist-upper-alpha{list-style-type:upper-alpha}.mw-parser-output .reflist-upper-roman{list-style-type:upper-roman}.mw-parser-output .reflist-lower-alpha{list-style-type:lower-alpha}.mw-parser-output .reflist-lower-greek{list-style-type:lower-greek}.mw-parser-output .reflist-lower-roman{list-style-type:lower-roman}</style><div class="reflist reflist-columns references-column-width" style="column-width: 25em;"> <ol class="references"> <li id="cite_note-physconst-mmu-1"><span class="mw-cite-backlink"><b><a href="#cite_ref-physconst-mmu_1-0">^</a></b></span> <span class="reference-text"><style data-mw-deduplicate="TemplateStyles:r1238218222">.mw-parser-output cite.citation{font-style:inherit;word-wrap:break-word}.mw-parser-output .citation q{quotes:"\"""\"""'""'"}.mw-parser-output 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.id-lock-registration a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-subscription a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .cs1-ws-icon a{background-size:contain;padding:0 1em 0 0}.mw-parser-output .cs1-code{color:inherit;background:inherit;border:none;padding:inherit}.mw-parser-output .cs1-hidden-error{display:none;color:var(--color-error,#d33)}.mw-parser-output .cs1-visible-error{color:var(--color-error,#d33)}.mw-parser-output .cs1-maint{display:none;color:#085;margin-left:0.3em}.mw-parser-output .cs1-kern-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right{padding-right:0.2em}.mw-parser-output .citation .mw-selflink{font-weight:inherit}@media screen{.mw-parser-output .cs1-format{font-size:95%}html.skin-theme-clientpref-night .mw-parser-output .cs1-maint{color:#18911f}}@media screen and (prefers-color-scheme:dark){html.skin-theme-clientpref-os .mw-parser-output .cs1-maint{color:#18911f}}</style><cite class="citation web cs1"><a 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(1937). <a rel="nofollow" class="external text" href="https://authors.library.caltech.edu/8618/1/NEDpr37.pdf">"Note on the Nature of Cosmic-Ray Particles"</a> <span class="cs1-format">(PDF)</span>. <i><a href="/wiki/Physical_Review" title="Physical Review">Physical Review</a></i>. <b>51</b> (10): <span class="nowrap">884–</span>886. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1937PhRv...51..884N">1937PhRv...51..884N</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1103%2FPhysRev.51.884">10.1103/PhysRev.51.884</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Physical+Review&rft.atitle=Note+on+the+Nature+of+Cosmic-Ray+Particles&rft.volume=51&rft.issue=10&rft.pages=%3Cspan+class%3D%22nowrap%22%3E884-%3C%2Fspan%3E886&rft.date=1937&rft_id=info%3Adoi%2F10.1103%2FPhysRev.51.884&rft_id=info%3Abibcode%2F1937PhRv...51..884N&rft.au=Neddermeyer%2C+S.H.&rft.au=Anderson%2C+C.D.&rft_id=https%3A%2F%2Fauthors.library.caltech.edu%2F8618%2F1%2FNEDpr37.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFStreet,_J.C.Stevenson,_E.C.1937" class="citation journal cs1">Street, J.C.; Stevenson, E.C. 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"Law of Conservation of Muons". <i><a href="/wiki/Physical_Review_Letters" title="Physical Review Letters">Physical Review Letters</a></i>. <b>6</b> (7): <span class="nowrap">381–</span>383. <a href="/wiki/Bibcode_(identifier)" class="mw-redirect" title="Bibcode (identifier)">Bibcode</a>:<a rel="nofollow" class="external text" href="https://ui.adsabs.harvard.edu/abs/1961PhRvL...6..381F">1961PhRvL...6..381F</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1103%2FPhysRevLett.6.381">10.1103/PhysRevLett.6.381</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Physical+Review+Letters&rft.atitle=Law+of+Conservation+of+Muons&rft.volume=6&rft.issue=7&rft.pages=%3Cspan+class%3D%22nowrap%22%3E381-%3C%2Fspan%3E383&rft.date=1961&rft_id=info%3Adoi%2F10.1103%2FPhysRevLett.6.381&rft_id=info%3Abibcode%2F1961PhRvL...6..381F&rft.au=Feinberg%2C+G.&rft.au=Weinberg%2C+S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFSerwayFaughn1995" class="citation book cs1">Serway; Faughn (1995). <i>College Physics</i> (4th ed.). <a href="/wiki/Saunders_(imprint)" title="Saunders (imprint)">Saunders</a>. p. 841.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=College+Physics&rft.pages=841&rft.edition=4th&rft.pub=Saunders&rft.date=1995&rft.au=Serway&rft.au=Faughn&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKnecht,_M.2003" class="citation book cs1">Knecht, M. (2003). <a rel="nofollow" class="external text" href="https://books.google.com/books?id=me6ftonVM_EC&q=%22The%20Anomalous%20Magnetic%20Moments%20of%20the%20Electron%20and%20the%20Muon%22&pg=PA265">"The Anomalous Magnetic Moments of the Electron and the Muon"</a>. In Duplantier, B.; Rivasseau, V. (eds.). <a href="/wiki/Poincar%C3%A9_Seminar" class="mw-redirect" title="Poincaré Seminar"><i>Poincaré Seminar 2002: Vacuum Energy – Renormalization</i></a>. Progress in Mathematical Physics. Vol. 30. <a href="/wiki/Birkh%C3%A4user_Verlag" class="mw-redirect" title="Birkhäuser Verlag">Birkhäuser Verlag</a>. p. 265. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-3-7643-0579-6" title="Special:BookSources/978-3-7643-0579-6"><bdi>978-3-7643-0579-6</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=bookitem&rft.atitle=The+Anomalous+Magnetic+Moments+of+the+Electron+and+the+Muon&rft.btitle=Poincar%C3%A9+Seminar+2002%3A+Vacuum+Energy+%E2%80%93+Renormalization&rft.series=Progress+in+Mathematical+Physics&rft.pages=265&rft.pub=Birkh%C3%A4user+Verlag&rft.date=2003&rft.isbn=978-3-7643-0579-6&rft.au=Knecht%2C+M.&rft_id=https%3A%2F%2Fbooks.google.com%2Fbooks%3Fid%3Dme6ftonVM_EC%26q%3D%2522The%2520Anomalous%2520Magnetic%2520Moments%2520of%2520the%2520Electron%2520and%2520the%2520Muon%2522%26pg%3DPA265&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFDerman,_E.2004" class="citation book cs1">Derman, E. (2004). <i>My Life as a Quant</i>. <a href="/wiki/John_Wiley_%26_Sons" class="mw-redirect" title="John Wiley & Sons">Wiley</a>. pp. <span class="nowrap">58–</span>62.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=My+Life+as+a+Quant&rft.pages=%3Cspan+class%3D%22nowrap%22%3E58-%3C%2Fspan%3E62&rft.pub=Wiley&rft.date=2004&rft.au=Derman%2C+E.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li></ul> </div> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2><span class="mw-editsection"><span class="mw-editsection-bracket">[</span><a href="/w/index.php?title=Muon&action=edit&section=16" title="Edit section: External links"><span>edit</span></a><span class="mw-editsection-bracket">]</span></span></div> <ul><li><span class="noviewer" typeof="mw:File"><a href="/wiki/File:Commons-logo.svg" class="mw-file-description"><img alt="" src="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/12px-Commons-logo.svg.png" decoding="async" width="12" height="16" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/18px-Commons-logo.svg.png 1.5x, //upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/24px-Commons-logo.svg.png 2x" data-file-width="1024" data-file-height="1376" /></a></span> Media related to <a href="https://commons.wikimedia.org/wiki/Category:Muons" class="extiw" title="commons:Category:Muons">Muons</a> at Wikimedia Commons</li> <li><a rel="nofollow" class="external text" href="https://apod.nasa.gov/apod/ap050828.html">NASA Astronomy Picture of the Day: Muon anomalous magnetic moment and supersymmetry (28 August 2005)</a></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://www.g-2.bnl.gov/">"g-2 experiment"</a>. <q>muon anomalous magnetic moment</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=g-2+experiment&rft_id=http%3A%2F%2Fwww.g-2.bnl.gov%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20060902054947/http://www.npl.uiuc.edu/exp/mulan/">"muLan experiment"</a>. Archived from <a rel="nofollow" class="external text" href="http://www.npl.uiuc.edu/exp/mulan/">the original</a> on 2 September 2006. <q>Measurement of the Positive Muon Lifetime</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=muLan+experiment&rft_id=http%3A%2F%2Fwww.npl.uiuc.edu%2Fexp%2Fmulan%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://pdg.lbl.gov/">"The Review of Particle Physics"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+Review+of+Particle+Physics&rft_id=http%3A%2F%2Fpdg.lbl.gov%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="http://twist.triumf.ca/">"The TRIUMF Weak Interaction Symmetry Test"</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+TRIUMF+Weak+Interaction+Symmetry+Test&rft_id=http%3A%2F%2Ftwist.triumf.ca%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite class="citation web cs1"><a rel="nofollow" class="external text" href="https://web.archive.org/web/20020325192213/http://meg.psi.ch/">"The MEG Experiment"</a>. Archived from <a rel="nofollow" class="external text" href="http://meg.psi.ch/">the original</a> on 25 March 2002. <q>Search for the decay Muon → Positron + Gamma</q></cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=The+MEG+Experiment&rft_id=http%3A%2F%2Fmeg.psi.ch%2F&rfr_id=info%3Asid%2Fen.wikipedia.org%3AMuon" class="Z3988"></span></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222" /><cite id="CITEREFKing" class="citation web cs1">King, Philip. <a rel="nofollow" class="external text" href="http://www.backstagescience.com/videos/ISIS_muons.html">"Making Muons"</a>. <i>Backstage Science</i>. <a href="/wiki/Brady_Haran" title="Brady Haran">Brady Haran</a>.</cite><span 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style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;"><a href="/wiki/Gaugino" title="Gaugino">Gauginos</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Gluino" title="Gluino">Gluino</a></li> <li><a href="/wiki/Gravitino" title="Gravitino">Gravitino</a></li> <li><a href="/wiki/Photino" title="Photino">Photino</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;">Others</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Axino" title="Axino">Axino</a></li> <li><a href="/wiki/Chargino" title="Chargino">Chargino</a></li> <li><a href="/wiki/Higgsino" title="Higgsino">Higgsino</a></li> <li><a href="/wiki/Neutralino" title="Neutralino">Neutralino</a></li> <li><a href="/wiki/Sfermion" title="Sfermion">Sfermion</a> (<a href="/wiki/Stop_squark" title="Stop squark">Stop squark</a>)</li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;">Others</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Axion" title="Axion">Axion</a></li> <li><a href="/wiki/Curvaton" title="Curvaton">Curvaton</a></li> <li><a href="/wiki/Dilaton" title="Dilaton">Dilaton</a></li> <li><a href="/wiki/Dual_graviton" title="Dual graviton">Dual graviton</a></li> <li><a href="/wiki/Graviphoton" title="Graviphoton">Graviphoton</a></li> <li><a href="/wiki/Graviton" title="Graviton">Graviton</a></li> <li><a href="/wiki/Inflaton" title="Inflaton">Inflaton</a></li> <li><a href="/wiki/Leptoquark" title="Leptoquark">Leptoquark</a></li> <li><a href="/wiki/Magnetic_monopole" title="Magnetic monopole">Magnetic monopole</a></li> <li><a href="/wiki/Majoron" title="Majoron">Majoron</a></li> <li><a href="/wiki/Majorana_fermion" title="Majorana fermion">Majorana fermion</a></li> <li><a href="/wiki/Dark_photon" title="Dark photon">Dark photon</a></li> <li><a href="/wiki/Preon" title="Preon">Preon</a></li> <li><a href="/wiki/Sterile_neutrino" title="Sterile neutrino">Sterile neutrino</a></li> <li><a href="/wiki/Tachyon" title="Tachyon">Tachyon</a></li> <li><a href="/wiki/W%E2%80%B2_and_Z%E2%80%B2_bosons" title="W′ and Z′ bosons">W′ and Z′ bosons</a></li> <li><a href="/wiki/X_and_Y_bosons" title="X and Y bosons">X and Y bosons</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Bound_state" title="Bound state">Composite</a></th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th id="Hadrons64" scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Hadron" title="Hadron">Hadrons</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;"><a href="/wiki/Baryon" title="Baryon">Baryons</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Nucleon" title="Nucleon">Nucleon</a> <ul><li><a href="/wiki/Proton" title="Proton">Proton</a></li> <li><a href="/wiki/Antiproton" title="Antiproton">Antiproton</a></li> <li><a href="/wiki/Neutron" title="Neutron">Neutron</a></li> <li><a href="/wiki/Antineutron" title="Antineutron">Antineutron</a></li></ul></li> <li><a href="/wiki/Delta_baryon" title="Delta baryon">Delta baryon</a></li> <li><a href="/wiki/Lambda_baryon" title="Lambda baryon">Lambda baryon</a></li> <li><a href="/wiki/Sigma_baryon" title="Sigma baryon">Sigma baryon</a></li> <li><a href="/wiki/Xi_baryon" title="Xi baryon">Xi baryon</a></li> <li><a href="/wiki/Omega_baryon" title="Omega baryon">Omega baryon</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;"><a href="/wiki/Meson" title="Meson">Mesons</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Pion" title="Pion">Pion</a></li> <li><a href="/wiki/Rho_meson" title="Rho meson">Rho meson</a></li> <li><a href="/wiki/Eta_meson" class="mw-redirect" title="Eta meson">Eta and eta prime mesons</a></li> <li><a href="/wiki/Bottom_eta_meson" title="Bottom eta meson">Bottom eta meson</a></li> <li><a href="/wiki/Phi_meson" title="Phi meson">Phi meson</a></li> <li><a href="/wiki/J/psi_meson" title="J/psi meson">J/psi meson</a></li> <li><a href="/wiki/Omega_meson" title="Omega meson">Omega meson</a></li> <li><a href="/wiki/Upsilon_meson" title="Upsilon meson">Upsilon meson</a></li> <li><a href="/wiki/Kaon" title="Kaon">Kaon</a></li> <li><a href="/wiki/B_meson" title="B meson">B meson</a></li> <li><a href="/wiki/D_meson" title="D meson">D meson</a></li> <li><a href="/wiki/Quarkonium" title="Quarkonium">Quarkonium</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;"><a href="/wiki/Exotic_hadron" title="Exotic hadron">Exotic hadrons</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Tetraquark" title="Tetraquark">Tetraquark</a> (<a href="/wiki/Double-charm_tetraquark" title="Double-charm tetraquark">Double-charm tetraquark</a>)</li> <li><a href="/wiki/Pentaquark" title="Pentaquark">Pentaquark</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;;font-weight:normal; text-align: center;">Others</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Atomic_nucleus" title="Atomic nucleus">Atomic nuclei</a></li> <li><a href="/wiki/Atom" title="Atom">Atoms</a></li> <li><a href="/wiki/Exotic_atom" title="Exotic atom">Exotic atoms</a> <ul><li><a href="/wiki/Positronium" title="Positronium">Positronium</a></li> <li><a href="/wiki/Muonium" title="Muonium">Muonium</a></li> <li><a href="/wiki/Tauonium" class="mw-redirect" title="Tauonium">Tauonium</a></li> <li><a href="/wiki/Onium" title="Onium">Onia</a></li> <li><a href="/wiki/Pionium" title="Pionium">Pionium</a></li> <li><a href="/wiki/Protonium" title="Protonium">Protonium</a></li></ul></li> <li><a href="/wiki/Superatom" title="Superatom">Superatoms</a></li> <li><a href="/wiki/Molecule" title="Molecule">Molecules</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/List_of_hypothetical_particles" title="List of hypothetical particles">Hypothetical</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><td colspan="2" class="navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"></div><table class="nowraplinks navbox-subgroup" style="border-spacing:0"><tbody><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;">Baryons</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Hexaquark" title="Hexaquark">Hexaquark</a></li> <li><a href="/wiki/Heptaquark" title="Heptaquark">Heptaquark</a></li> <li><a href="/wiki/Skyrmion" title="Skyrmion">Skyrmion</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;">Mesons</th><td class="navbox-list-with-group navbox-list navbox-even" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Glueball" title="Glueball">Glueball</a></li> <li><a href="/wiki/Theta_meson" title="Theta meson">Theta meson</a></li> <li><a href="/wiki/T_meson" title="T meson">T meson</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;;font-weight:normal; text-align: center;">Others</th><td class="navbox-list-with-group navbox-list navbox-odd" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Mesonic_molecule" title="Mesonic molecule">Mesonic molecule</a></li> <li><a href="/wiki/Pomeron" title="Pomeron">Pomeron</a></li> <li><a href="/wiki/Diquark" title="Diquark">Diquark</a></li> <li><a href="/wiki/R-hadron" title="R-hadron">R-hadron</a></li></ul> </div></td></tr></tbody></table><div></div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%"><a href="/wiki/Quasiparticle" title="Quasiparticle">Quasiparticles</a></th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Anyon" title="Anyon">Anyon</a></li> <li><a href="/wiki/Davydov_soliton" title="Davydov soliton">Davydov soliton</a></li> <li><a href="/wiki/Dropleton" title="Dropleton">Dropleton</a></li> <li><a href="/wiki/Exciton" title="Exciton">Exciton</a></li> <li><a href="/wiki/Fracton_(subdimensional_particle)" title="Fracton (subdimensional particle)">Fracton</a></li> <li><a href="/wiki/Electron_hole" title="Electron hole">Hole</a></li> <li><a href="/wiki/Magnon" title="Magnon">Magnon</a></li> <li><a href="/wiki/Phonon" title="Phonon">Phonon</a></li> <li><a href="/wiki/Plasmaron" title="Plasmaron">Plasmaron</a></li> <li><a href="/wiki/Plasmon" title="Plasmon">Plasmon</a></li> <li><a href="/wiki/Polariton" title="Polariton">Polariton</a></li> <li><a href="/wiki/Polaron" title="Polaron">Polaron</a></li> <li><a href="/wiki/Roton" title="Roton">Roton</a></li> <li><a href="/wiki/Trion_(physics)" title="Trion (physics)">Trion</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Lists</th><td class="navbox-list-with-group navbox-list navbox-odd hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/List_of_baryons" title="List of baryons">Baryons</a></li> <li><a href="/wiki/List_of_mesons" title="List of mesons">Mesons</a></li> <li><a href="/wiki/List_of_particles" title="List of particles">Particles</a></li> <li><a href="/wiki/List_of_quasiparticles" title="List of quasiparticles">Quasiparticles</a></li> <li><a href="/wiki/Timeline_of_particle_discoveries" title="Timeline of particle discoveries">Timeline of particle discoveries</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="text-align: center;;width:1%">Related</th><td class="navbox-list-with-group navbox-list navbox-even hlist" style="width:100%;padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/History_of_subatomic_physics" title="History of subatomic physics">History of subatomic physics</a> <ul><li><a href="/wiki/Timeline_of_atomic_and_subatomic_physics" title="Timeline of atomic and subatomic physics">timeline</a></li></ul></li> <li><a href="/wiki/Standard_Model" title="Standard Model">Standard Model</a> <ul><li><a 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