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kaon mixing </div> </a> <ul id="toc-Neutral_kaon_mixing-sublist" class="vector-toc-list"> <li id="toc-Mixing" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Mixing"> <div class="vector-toc-text"> 4.1.1 Mixing </div> </a> <ul id="toc-Mixing-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Oscillation" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Oscillation"> <div class="vector-toc-text"> 4.1.2 Oscillation </div> </a> <ul id="toc-Oscillation-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Regeneration" class="vector-toc-list-item vector-toc-level-3"> <a class="vector-toc-link" href="#Regeneration"> <div class="vector-toc-text"> 4.1.3 Regeneration </div> </a> <ul id="toc-Regeneration-sublist" class="vector-toc-list"> </ul> </li> </ul> </li> <li id="toc-CP_violation" class="vector-toc-list-item vector-toc-level-2"> <a class="vector-toc-link" href="#CP_violation"> <div class="vector-toc-text"> 4.2 CP violation </div> </a> <ul id="toc-CP_violation-sublist" class="vector-toc-list"> </ul> </li> </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"> 5 See also </div> </a> <ul id="toc-See_also-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Footnotes" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Footnotes"> <div class="vector-toc-text"> 6 Footnotes </div> </a> <ul id="toc-Footnotes-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"> 7 References </div> </a> <ul id="toc-References-sublist" class="vector-toc-list"> </ul> </li> <li id="toc-Bibliography" class="vector-toc-list-item vector-toc-level-1 vector-toc-list-item-expanded"> <a class="vector-toc-link" href="#Bibliography"> <div class="vector-toc-text"> 8 Bibliography </div> </a> <ul id="toc-Bibliography-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"> 9 External links </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" > Toggle the table of contents </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">Kaon</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 38 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-38" aria-hidden="true" > 38 languages </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/Kaon" title="Kaon – Afrikaans" lang="af" hreflang="af" data-title="Kaon" data-language-autonym="Afrikaans" data-language-local-name="Afrikaans" class="interlanguage-link-target">Afrikaans</a></li><li class="interlanguage-link interwiki-ar mw-list-item"><a href="https://ar.wikipedia.org/wiki/%D9%83%D8%A7%D9%88%D9%86" title="كاون – Arabic" lang="ar" hreflang="ar" data-title="كاون" data-language-autonym="العربية" data-language-local-name="Arabic" class="interlanguage-link-target">العربية</a></li><li class="interlanguage-link interwiki-be mw-list-item"><a href="https://be.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BE%D0%BD%D1%8B" title="Каоны – Belarusian" lang="be" hreflang="be" data-title="Каоны" data-language-autonym="Беларуская" data-language-local-name="Belarusian" class="interlanguage-link-target">Беларуская</a></li><li class="interlanguage-link interwiki-ca mw-list-item"><a href="https://ca.wikipedia.org/wiki/Ka%C3%B3_(f%C3%ADsica)" title="Kaó (física) – Catalan" lang="ca" hreflang="ca" data-title="Kaó (física)" data-language-autonym="Català" data-language-local-name="Catalan" class="interlanguage-link-target">Català</a></li><li class="interlanguage-link interwiki-cs mw-list-item"><a href="https://cs.wikipedia.org/wiki/Kaon" title="Kaon – Czech" lang="cs" hreflang="cs" data-title="Kaon" data-language-autonym="Čeština" data-language-local-name="Czech" class="interlanguage-link-target">Čeština</a></li><li class="interlanguage-link interwiki-da mw-list-item"><a href="https://da.wikipedia.org/wiki/Kaon" title="Kaon – Danish" lang="da" hreflang="da" data-title="Kaon" data-language-autonym="Dansk" data-language-local-name="Danish" class="interlanguage-link-target">Dansk</a></li><li class="interlanguage-link interwiki-de mw-list-item"><a href="https://de.wikipedia.org/wiki/Kaon" title="Kaon – German" lang="de" hreflang="de" data-title="Kaon" data-language-autonym="Deutsch" data-language-local-name="German" class="interlanguage-link-target">Deutsch</a></li><li class="interlanguage-link interwiki-et mw-list-item"><a href="https://et.wikipedia.org/wiki/Kaaon" title="Kaaon – Estonian" lang="et" hreflang="et" data-title="Kaaon" data-language-autonym="Eesti" data-language-local-name="Estonian" class="interlanguage-link-target">Eesti</a></li><li class="interlanguage-link interwiki-es mw-list-item"><a href="https://es.wikipedia.org/wiki/Ka%C3%B3n" title="Kaón – Spanish" lang="es" hreflang="es" data-title="Kaón" data-language-autonym="Español" data-language-local-name="Spanish" class="interlanguage-link-target">Español</a></li><li class="interlanguage-link interwiki-fa mw-list-item"><a href="https://fa.wikipedia.org/wiki/%DA%A9%D8%A7%D8%A6%D9%88%D9%86" title="کائون – Persian" lang="fa" hreflang="fa" data-title="کائون" data-language-autonym="فارسی" data-language-local-name="Persian" class="interlanguage-link-target">فارسی</a></li><li class="interlanguage-link interwiki-fr mw-list-item"><a href="https://fr.wikipedia.org/wiki/Kaon" title="Kaon – French" lang="fr" hreflang="fr" data-title="Kaon" data-language-autonym="Français" data-language-local-name="French" class="interlanguage-link-target">Français</a></li><li class="interlanguage-link interwiki-gl mw-list-item"><a href="https://gl.wikipedia.org/wiki/Ka%C3%B3n" title="Kaón – Galician" lang="gl" hreflang="gl" data-title="Kaón" data-language-autonym="Galego" data-language-local-name="Galician" class="interlanguage-link-target">Galego</a></li><li class="interlanguage-link interwiki-ko mw-list-item"><a href="https://ko.wikipedia.org/wiki/%EC%BC%80%EC%9D%B4_%EC%A4%91%EA%B0%84%EC%9E%90" title="케이 중간자 – Korean" lang="ko" hreflang="ko" data-title="케이 중간자" data-language-autonym="한국어" data-language-local-name="Korean" class="interlanguage-link-target">한국어</a></li><li class="interlanguage-link interwiki-hr mw-list-item"><a href="https://hr.wikipedia.org/wiki/Kaon" title="Kaon – Croatian" lang="hr" hreflang="hr" data-title="Kaon" data-language-autonym="Hrvatski" data-language-local-name="Croatian" class="interlanguage-link-target">Hrvatski</a></li><li class="interlanguage-link interwiki-id mw-list-item"><a href="https://id.wikipedia.org/wiki/Kaon" title="Kaon – Indonesian" lang="id" hreflang="id" data-title="Kaon" data-language-autonym="Bahasa Indonesia" data-language-local-name="Indonesian" class="interlanguage-link-target">Bahasa Indonesia</a></li><li class="interlanguage-link interwiki-it mw-list-item"><a href="https://it.wikipedia.org/wiki/Kaone" title="Kaone – Italian" lang="it" hreflang="it" data-title="Kaone" data-language-autonym="Italiano" data-language-local-name="Italian" class="interlanguage-link-target">Italiano</a></li><li class="interlanguage-link interwiki-he mw-list-item"><a href="https://he.wikipedia.org/wiki/%D7%A7%D7%90%D7%95%D7%9F" title="קאון – Hebrew" lang="he" hreflang="he" data-title="קאון" data-language-autonym="עברית" data-language-local-name="Hebrew" class="interlanguage-link-target">עברית</a></li><li class="interlanguage-link interwiki-ka mw-list-item"><a href="https://ka.wikipedia.org/wiki/%E1%83%99%E1%83%90%E1%83%9D%E1%83%9C%E1%83%98" title="კაონი – Georgian" lang="ka" hreflang="ka" data-title="კაონი" data-language-autonym="ქართული" data-language-local-name="Georgian" class="interlanguage-link-target">ქართული</a></li><li class="interlanguage-link interwiki-hu mw-list-item"><a href="https://hu.wikipedia.org/wiki/Kaon_(r%C3%A9szecske)" title="Kaon (részecske) – Hungarian" lang="hu" hreflang="hu" data-title="Kaon (részecske)" data-language-autonym="Magyar" data-language-local-name="Hungarian" class="interlanguage-link-target">Magyar</a></li><li class="interlanguage-link interwiki-mk mw-list-item"><a href="https://mk.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BE%D0%BD" title="Каон – Macedonian" lang="mk" hreflang="mk" data-title="Каон" data-language-autonym="Македонски" data-language-local-name="Macedonian" class="interlanguage-link-target">Македонски</a></li><li class="interlanguage-link interwiki-nl mw-list-item"><a href="https://nl.wikipedia.org/wiki/Kaon" title="Kaon – Dutch" lang="nl" hreflang="nl" data-title="Kaon" data-language-autonym="Nederlands" data-language-local-name="Dutch" class="interlanguage-link-target">Nederlands</a></li><li class="interlanguage-link interwiki-ja mw-list-item"><a href="https://ja.wikipedia.org/wiki/K%E4%B8%AD%E9%96%93%E5%AD%90" title="K中間子 – Japanese" lang="ja" hreflang="ja" data-title="K中間子" data-language-autonym="日本語" data-language-local-name="Japanese" class="interlanguage-link-target">日本語</a></li><li class="interlanguage-link interwiki-no mw-list-item"><a href="https://no.wikipedia.org/wiki/Kaon" title="Kaon – Norwegian Bokmål" lang="nb" hreflang="nb" data-title="Kaon" data-language-autonym="Norsk bokmål" data-language-local-name="Norwegian Bokmål" class="interlanguage-link-target">Norsk bokmål</a></li><li class="interlanguage-link interwiki-nn mw-list-item"><a href="https://nn.wikipedia.org/wiki/Kaon" title="Kaon – Norwegian Nynorsk" lang="nn" hreflang="nn" data-title="Kaon" data-language-autonym="Norsk nynorsk" data-language-local-name="Norwegian Nynorsk" class="interlanguage-link-target">Norsk nynorsk</a></li><li class="interlanguage-link interwiki-pnb mw-list-item"><a href="https://pnb.wikipedia.org/wiki/%DA%A9%D8%A7%D8%A4%D9%86" title="کاؤن – Western Punjabi" lang="pnb" hreflang="pnb" data-title="کاؤن" data-language-autonym="پنجابی" data-language-local-name="Western Punjabi" class="interlanguage-link-target">پنجابی</a></li><li class="interlanguage-link interwiki-pl mw-list-item"><a href="https://pl.wikipedia.org/wiki/Kaon" title="Kaon – Polish" lang="pl" hreflang="pl" data-title="Kaon" data-language-autonym="Polski" data-language-local-name="Polish" class="interlanguage-link-target">Polski</a></li><li class="interlanguage-link interwiki-pt mw-list-item"><a href="https://pt.wikipedia.org/wiki/K%C3%A1on" title="Káon – Portuguese" lang="pt" hreflang="pt" data-title="Káon" data-language-autonym="Português" data-language-local-name="Portuguese" class="interlanguage-link-target">Português</a></li><li class="interlanguage-link interwiki-ru mw-list-item"><a href="https://ru.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BE%D0%BD" title="Каон – Russian" lang="ru" hreflang="ru" data-title="Каон" data-language-autonym="Русский" data-language-local-name="Russian" class="interlanguage-link-target">Русский</a></li><li class="interlanguage-link interwiki-simple mw-list-item"><a href="https://simple.wikipedia.org/wiki/Kaon" title="Kaon – Simple English" lang="en-simple" hreflang="en-simple" data-title="Kaon" data-language-autonym="Simple English" data-language-local-name="Simple English" class="interlanguage-link-target">Simple English</a></li><li class="interlanguage-link interwiki-sk mw-list-item"><a href="https://sk.wikipedia.org/wiki/Ka%C3%B3n" title="Kaón – Slovak" lang="sk" hreflang="sk" data-title="Kaón" data-language-autonym="Slovenčina" data-language-local-name="Slovak" class="interlanguage-link-target">Slovenčina</a></li><li class="interlanguage-link interwiki-sl mw-list-item"><a href="https://sl.wikipedia.org/wiki/Kaon" title="Kaon – Slovenian" lang="sl" hreflang="sl" data-title="Kaon" data-language-autonym="Slovenščina" data-language-local-name="Slovenian" class="interlanguage-link-target">Slovenščina</a></li><li class="interlanguage-link interwiki-fi mw-list-item"><a href="https://fi.wikipedia.org/wiki/Kaoni" title="Kaoni – Finnish" lang="fi" hreflang="fi" data-title="Kaoni" data-language-autonym="Suomi" data-language-local-name="Finnish" class="interlanguage-link-target">Suomi</a></li><li class="interlanguage-link interwiki-sv mw-list-item"><a href="https://sv.wikipedia.org/wiki/Kaon" title="Kaon – Swedish" lang="sv" hreflang="sv" data-title="Kaon" data-language-autonym="Svenska" data-language-local-name="Swedish" class="interlanguage-link-target">Svenska</a></li><li class="interlanguage-link interwiki-tr mw-list-item"><a href="https://tr.wikipedia.org/wiki/Kaon" title="Kaon – Turkish" lang="tr" hreflang="tr" data-title="Kaon" data-language-autonym="Türkçe" data-language-local-name="Turkish" class="interlanguage-link-target">Türkçe</a></li><li class="interlanguage-link interwiki-uk mw-list-item"><a href="https://uk.wikipedia.org/wiki/%D0%9A%D0%B0%D0%BE%D0%BD%D0%B8" title="Каони – Ukrainian" lang="uk" hreflang="uk" data-title="Каони" data-language-autonym="Українська" data-language-local-name="Ukrainian" class="interlanguage-link-target">Українська</a></li><li class="interlanguage-link interwiki-wuu mw-list-item"><a href="https://wuu.wikipedia.org/wiki/K%E4%BB%8B%E5%AD%90" title="K介子 – Wu" lang="wuu" hreflang="wuu" data-title="K介子" data-language-autonym="吴语" data-language-local-name="Wu" class="interlanguage-link-target">吴语</a></li><li class="interlanguage-link interwiki-zh-yue mw-list-item"><a href="https://zh-yue.wikipedia.org/wiki/K%E4%BB%8B%E5%AD%90" title="K介子 – Cantonese" lang="yue" hreflang="yue" data-title="K介子" data-language-autonym="粵語" data-language-local-name="Cantonese" class="interlanguage-link-target">粵語</a></li><li class="interlanguage-link interwiki-zh mw-list-item"><a href="https://zh.wikipedia.org/wiki/K%E4%BB%8B%E5%AD%90" title="K介子 – Chinese" lang="zh" hreflang="zh" data-title="K介子" data-language-autonym="中文" data-language-local-name="Chinese" 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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">Quantum particle</div> <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><div role="note" class="hatnote navigation-not-searchable">For other uses, see <a href="/wiki/Kaon_(disambiguation)" class="mw-disambig" title="Kaon (disambiguation)">Kaon (disambiguation)</a>.</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1236090951"><div role="note" class="hatnote navigation-not-searchable">Not to be confused with <a href="/wiki/K%C5%8Dan" class="mw-redirect" title="Kōan">Kōan</a>.</div> <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">Kaon</caption><tbody><tr><th scope="row" class="infobox-label"><a href="/wiki/Particle#Composition" title="Particle">Composition</a></th><td class="infobox-data"> K+ : u s K0 : d s K− : s u </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/Bosonic" class="mw-redirect" title="Bosonic">Bosonic</a></td></tr><tr><th scope="row" class="infobox-label">Family</th><td class="infobox-data"><a href="/wiki/Meson" title="Meson">Mesons</a></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/Strong_interaction" title="Strong interaction">Strong</a>, <a href="/wiki/Weak_interaction" title="Weak interaction">weak</a>, <a href="/wiki/Electromagnetic_interaction" class="mw-redirect" title="Electromagnetic interaction">electromagnetic</a>, <a href="/wiki/Gravity" title="Gravity">gravitational</a></td></tr><tr><th scope="row" class="infobox-label">Symbol</th><td class="infobox-data"> K+ , K0 , K− </td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Antiparticle" title="Antiparticle">Antiparticle</a></th><td class="infobox-data"> K+ : K− K0 : K0 K− : K+ </td></tr><tr><th scope="row" class="infobox-label">Discovered</th><td class="infobox-data">1947 (<a href="/wiki/Clifford_Butler" class="mw-redirect" title="Clifford Butler">Clifford Butler</a> and <a href="/wiki/George_Rochester" title="George Rochester">George Rochester</a> at <a href="/wiki/Department_of_Physics_and_Astronomy,_University_of_Manchester" title="Department of Physics and Astronomy, University of Manchester">Department of Physics and Astronomy, University of Manchester</a>)</td></tr><tr><th scope="row" class="infobox-label">Types</th><td class="infobox-data">4</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Invariant_mass" title="Invariant mass">Mass</a></th><td class="infobox-data"> K± : 493.677±0.016 <a href="/wiki/Electronvolt#Mass" title="Electronvolt">MeV/c2</a> K0 : 497.611±0.013 MeV/c2</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"> K± : (1.2380±0.0020)×10−8 <a href="/wiki/Second" title="Second">s</a> K S: (8.954±0.004)×10−11 s K L: (5.116±0.021)×10−8 s</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"> K± : ±1 <a href="/wiki/Elementary_charge" title="Elementary charge">e</a> K0 : 0 e</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Spin_(physics)" title="Spin (physics)">Spin</a></th><td class="infobox-data">0 <a href="/wiki/Reduced_Planck_constant" class="mw-redirect" title="Reduced Planck constant">ħ</a></td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Strangeness" title="Strangeness">Strangeness</a></th><td class="infobox-data"> K+ , K0 : +1 K− , K0 : −1</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Isospin" title="Isospin">Isospin</a></th><td class="infobox-data"> K+ , K0 : +<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>⁠1/2⁠ K0 , K− : −<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1214402035">⁠1/2⁠</td></tr><tr><th scope="row" class="infobox-label"><a href="/wiki/Parity_(physics)" title="Parity (physics)">Parity</a></th><td class="infobox-data">−1</td></tr></tbody></table><figure typeof="mw:File/Thumb"><a href="/wiki/File:Kaon-Decay.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Kaon-Decay.svg/300px-Kaon-Decay.svg.png" decoding="async" width="300" height="135" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/7/70/Kaon-Decay.svg/450px-Kaon-Decay.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/7/70/Kaon-Decay.svg/600px-Kaon-Decay.svg.png 2x" data-file-width="540" data-file-height="243" /></a><figcaption> The decay of a kaon ( K+ ) into three <a href="/wiki/Pion" title="Pion">pions</a> (2  π+ , 1  π− ) is a process that involves both <a href="/wiki/Weak_interaction" title="Weak interaction">weak</a> and <a href="/wiki/Strong_interaction" title="Strong interaction">strong interactions</a>. Weak interactions : The <a href="/wiki/Strange_antiquark" class="mw-redirect" title="Strange antiquark">strange antiquark</a> ( s ) of the kaon transmutes into an <a href="/wiki/Up_antiquark" class="mw-redirect" title="Up antiquark">up antiquark</a> ( u ) by the emission of a <a href="/wiki/W_and_Z_bosons" title="W and Z bosons"> W+ boson</a>; the W+ boson subsequently decays into a <a href="/wiki/Down_antiquark" class="mw-redirect" title="Down antiquark">down antiquark</a>  ( d ) and an <a href="/wiki/Up_quark" title="Up quark">up quark</a> ( u ). Strong interactions: An up quark ( u ) emits a <a href="/wiki/Gluon" title="Gluon">gluon</a> ( g ) which decays into a down quark ( d ) and a down antiquark ( d ).</figcaption></figure> In <a href="/wiki/Particle_physics" title="Particle physics">particle physics</a>, a kaon, also called a K meson and denoted K ,<a href="#cite_note-1">[a]</a> is any of a group of four <a href="/wiki/Meson" title="Meson">mesons</a> distinguished by a <a href="/wiki/Quantum_number" title="Quantum number">quantum number</a> called <a href="/wiki/Strangeness_(particle_physics)" class="mw-redirect" title="Strangeness (particle physics)">strangeness</a>. In the <a href="/wiki/Quark_model" title="Quark model">quark model</a> they are understood to be <a href="/wiki/Bound_states" class="mw-redirect" title="Bound states">bound states</a> of a <a href="/wiki/Strange_quark" title="Strange quark">strange quark</a> (or antiquark) and an <a href="/wiki/Up_quark" title="Up quark">up</a> or <a href="/wiki/Down_quark" title="Down quark">down</a> antiquark (or quark). Kaons have proved to be a copious source of information on the nature of <a href="/wiki/Fundamental_interactions" class="mw-redirect" title="Fundamental interactions">fundamental interactions</a> since their discovery by <a href="/wiki/George_Rochester" title="George Rochester">George Rochester</a> and <a href="/wiki/Clifford_Butler" class="mw-redirect" title="Clifford Butler">Clifford Butler</a> at the <a href="/wiki/Department_of_Physics_and_Astronomy,_University_of_Manchester" title="Department of Physics and Astronomy, University of Manchester">Department of Physics and Astronomy, University of Manchester</a> in <a href="/wiki/Cosmic_ray" title="Cosmic ray">cosmic rays</a> in 1947. They were essential in establishing the foundations of the <a href="/wiki/Standard_Model" title="Standard Model">Standard Model</a> of particle physics, such as the <a href="/wiki/Quark_model" title="Quark model">quark model</a> of <a href="/wiki/Hadron" title="Hadron">hadrons</a> and the theory of <a href="/wiki/Cabibbo%E2%80%93Kobayashi%E2%80%93Maskawa_matrix" title="Cabibbo–Kobayashi–Maskawa matrix">quark mixing</a> (the latter was acknowledged by a <a href="/wiki/Nobel_Prize_in_Physics" title="Nobel Prize in Physics">Nobel Prize in Physics</a> in 2008). Kaons have played a distinguished role in our understanding of fundamental <a href="/wiki/Conservation_law_(physics)" class="mw-redirect" title="Conservation law (physics)">conservation laws</a>: <a href="/wiki/CP_violation" title="CP violation">CP violation</a>, a phenomenon generating the observed matter–antimatter asymmetry of the universe, was discovered in the kaon system in 1964 (which was acknowledged by a Nobel Prize in 1980). Moreover, direct CP violation was discovered in the kaon decays in the early 2000s by the <a href="/wiki/NA48_experiment" title="NA48 experiment">NA48 experiment</a> at <a href="/wiki/CERN" title="CERN">CERN</a> and the KTeV experiment at <a href="/wiki/Fermilab" title="Fermilab">Fermilab</a>. <meta property="mw:PageProp/toc" /> <div class="mw-heading mw-heading2"><h2 id="Basic_properties">Basic properties</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=1" title="Edit section: Basic properties">edit</a>]</div> The four kaons are: <ol><li> K− , negatively charged (containing a <a href="/wiki/Strange_quark" title="Strange quark">strange quark</a> and an <a href="/wiki/Up_quark" title="Up quark">up antiquark</a>) has mass 493.677±0.013 MeV and <a href="/wiki/Mean_lifetime" class="mw-redirect" title="Mean lifetime">mean lifetime</a> (1.2380±0.0020)×10−8 s.</li> <li> K+ (<a href="/wiki/Antiparticle" title="Antiparticle">antiparticle</a> of above) positively charged (containing an <a href="/wiki/Up_quark" title="Up quark">up quark</a> and a <a href="/wiki/Strange_quark" title="Strange quark">strange antiquark</a>) must (by <a href="/wiki/CPT_invariance" class="mw-redirect" title="CPT invariance">CPT invariance</a>) have mass and lifetime equal to that of K− . Experimentally, the mass difference is 0.032±0.090 MeV, consistent with zero; the difference in lifetimes is (0.11±0.09)×10−8 s, also consistent with zero.</li> <li> K0 , neutrally charged (containing a <a href="/wiki/Down_quark" title="Down quark">down quark</a> and a <a href="/wiki/Strange_quark" title="Strange quark">strange antiquark</a>) has mass 497.648±0.022 MeV. It has mean squared <a href="/wiki/Charge_radius" title="Charge radius">charge radius</a> of −0.076±0.01 <a href="/wiki/Square_metre" title="Square metre">fm2</a>.</li> <li> K0 , neutrally charged (antiparticle of above) (containing a <a href="/wiki/Strange_quark" title="Strange quark">strange quark</a> and a <a href="/wiki/Down_quark" title="Down quark">down antiquark</a>) has the same mass.</li></ol> As the <a href="/wiki/Quark_model" title="Quark model">quark model</a> shows, assignments that the kaons form two <a href="/wiki/Doublet_state" title="Doublet state">doublets</a> of <a href="/wiki/Isospin" title="Isospin">isospin</a>; that is, they belong to the <a href="/wiki/Fundamental_representation" title="Fundamental representation">fundamental representation</a> of <a href="/wiki/SU(2)" class="mw-redirect" title="SU(2)">SU(2)</a> called the 2. One doublet of strangeness +1 contains the K+ and the K0 . The antiparticles form the other doublet (of strangeness −1). <table class="wikitable sortable" style="text-align: center;"> <caption>Properties of kaons </caption> <tbody><tr> <th class="unsortable">Particle name </th> <th>Particle symbol </th> <th>Antiparticle symbol </th> <th class="unsortable">Quark content </th> <th><a href="/wiki/Rest_mass" class="mw-redirect" title="Rest mass">Rest mass</a> (<a href="/wiki/Electron_volt" class="mw-redirect" title="Electron volt">MeV</a>/<a href="/wiki/Speed_of_light" title="Speed of light">c</a>2) </th> <th><a href="/wiki/Isospin" title="Isospin">I</a><a href="/wiki/G_parity" class="mw-redirect" title="G parity">G</a> </th> <th><a href="/wiki/Total_angular_momentum" class="mw-redirect" title="Total angular momentum">J</a><a href="/wiki/Parity_(physics)" title="Parity (physics)">P</a><a href="/wiki/C_parity" title="C parity">C</a> </th> <th><a href="/wiki/Strangeness" title="Strangeness">S</a> </th> <th><a href="/wiki/Charm_(quantum_number)" title="Charm (quantum number)">C</a> </th> <th><a href="/wiki/Bottomness" title="Bottomness">B'</a> </th> <th><a href="/wiki/Mean_lifetime" class="mw-redirect" title="Mean lifetime">Mean lifetime</a> (<a href="/wiki/Second" title="Second">s</a>) </th> <th class="unsortable">Commonly decays to (>5% of decays) </th></tr> <tr> <td>Kaon<a href="#cite_note-PDGKaon-2">[1]</a> </td> <td style="text-align:center;"><a class="mw-selflink selflink"> K+ </a> </td> <td style="text-align:center;"><a class="mw-selflink selflink"> K− </a> </td> <td style="text-align:center;"><a href="/wiki/Up_quark" title="Up quark"> u </a><a href="/wiki/Strange_antiquark" class="mw-redirect" title="Strange antiquark"> s </a> </td> <td style="text-align:left;">493.677±0.016 </td> <td style="text-align:center;"><style data-mw-deduplicate="TemplateStyles:r1154941027">.mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.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>1⁄2 </td> <td style="text-align:center;">0− </td> <td style="text-align:center;">1 </td> <td style="text-align:center;">0 </td> <td style="text-align:center;">0 </td> <td style="text-align:right;">(1.2380±0.0020)×10−8 </td> <td style="text-align:left;"><a href="/wiki/Antimuon" class="mw-redirect" title="Antimuon"> μ+ </a> + <a href="/wiki/Muon_neutrino" title="Muon neutrino"> ν μ</a> or <a href="/wiki/Pion" title="Pion"> π+ </a> + <a href="/wiki/Pion" title="Pion"> π0 </a> or <a href="/wiki/Pion" title="Pion"> π+ </a> + <a href="/wiki/Pion" title="Pion"> π+ </a> + <a href="/wiki/Pion" title="Pion"> π− </a> or <a href="/wiki/Pion" title="Pion"> π0 </a> + <a href="/wiki/Positron" title="Positron"> e+ </a> + <a href="/wiki/Electron_neutrino" title="Electron neutrino"> ν e</a> </td></tr> <tr> <td>Kaon<a href="#cite_note-PDGKaon0-3">[2]</a> </td> <td style="text-align:center;"><a class="mw-selflink selflink"> K0 </a> </td> <td style="text-align:center;"><a class="mw-selflink selflink"> K0 </a> </td> <td style="text-align:center;"><a href="/wiki/Down_quark" title="Down quark"> d </a><a href="/wiki/Strange_antiquark" class="mw-redirect" title="Strange antiquark"> s </a> </td> <td style="text-align:left;">497.611±0.013 </td> <td style="text-align:center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1154941027">1⁄2 </td> <td style="text-align:center;">0− </td> <td style="text-align:center;">1 </td> <td style="text-align:center;">0 </td> <td style="text-align:center;">0 </td> <td style="text-align:center;"><a href="#endnote_strongforce">[§]</a> </td> <td style="text-align:center;"><a href="#endnote_strongforce">[§]</a> </td></tr> <tr> <td>K-Short<a href="#cite_note-PDGK-short-4">[3]</a> </td> <td style="text-align:center;"><a class="mw-selflink selflink"> K0 S</a> </td> <td style="text-align:center;">Self </td> <td style="text-align:center;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathrm {\tfrac {d{\bar {s}}-s{\bar {d}}}{\sqrt {2}}} \,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mfrac> <mrow> <mi mathvariant="normal">d</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi mathvariant="normal">s</mi> <mo stretchy="false">¯</mo> </mover> </mrow> </mrow> <mo>−</mo> <mi mathvariant="normal">s</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi mathvariant="normal">d</mi> <mo stretchy="false">¯</mo> </mover> </mrow> </mrow> </mrow> <msqrt> <mn>2</mn> </msqrt> </mfrac> </mstyle> </mrow> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathrm {\tfrac {d{\bar {s}}-s{\bar {d}}}{\sqrt {2}}} \,}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/2783c2ea3ab6536304513941f802c8ea9d2ebdce" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:5.8ex; height:4.676ex;" alt="{\displaystyle \mathrm {\tfrac {d{\bar {s}}-s{\bar {d}}}{\sqrt {2}}} \,}"><a href="#endnote_Kaon">[†]</a><a href="#cite_note-cambridge-5">[4]</a><a href="#cite_note-southampton-6">[5]</a> </td> <td style="text-align:center;">497.611±0.013<a href="#endnote_Kaonmass">[‡]</a> </td> <td style="text-align:center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1154941027">1⁄2 </td> <td style="text-align:center;">0− </td> <td style="text-align:center;"><a href="/wiki/List_of_mesons#Notes_on_neutral_kaons" title="List of mesons">[*]</a> </td> <td style="text-align:center;">0 </td> <td style="text-align:center;">0 </td> <td style="text-align:right;">(8.954±0.004)×10−11 </td> <td style="text-align:left;"><a href="/wiki/Pion" title="Pion"> π+ </a> + <a href="/wiki/Pion" title="Pion"> π− </a> or <a href="/wiki/Pion" title="Pion"> π0 </a> + <a href="/wiki/Pion" title="Pion"> π0 </a> </td></tr> <tr> <td>K-Long<a href="#cite_note-PDGK-long-7">[6]</a> </td> <td style="text-align:center;"><a class="mw-selflink selflink"> K0 L</a> </td> <td style="text-align:center;">Self </td> <td style="text-align:center;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathrm {\tfrac {d{\bar {s}}+s{\bar {d}}}{\sqrt {2}}} \,}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="false" scriptlevel="0"> <mfrac> <mrow> <mi mathvariant="normal">d</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi mathvariant="normal">s</mi> <mo stretchy="false">¯</mo> </mover> </mrow> </mrow> <mo>+</mo> <mi mathvariant="normal">s</mi> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mover> <mi mathvariant="normal">d</mi> <mo stretchy="false">¯</mo> </mover> </mrow> </mrow> </mrow> <msqrt> <mn>2</mn> </msqrt> </mfrac> </mstyle> </mrow> <mspace width="thinmathspace" /> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \mathrm {\tfrac {d{\bar {s}}+s{\bar {d}}}{\sqrt {2}}} \,}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/552d976a4a77e20e35ef26bdb3112400d78efea9" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -1.838ex; width:5.8ex; height:4.676ex;" alt="{\displaystyle \mathrm {\tfrac {d{\bar {s}}+s{\bar {d}}}{\sqrt {2}}} \,}"><a href="#endnote_Kaon">[†]</a><a href="#cite_note-cambridge-5">[4]</a><a href="#cite_note-southampton-6">[5]</a> </td> <td style="text-align:left;">497.611±0.013<a href="#endnote_Kaonmass">[‡]</a> </td> <td style="text-align:center;"><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1154941027">1⁄2 </td> <td style="text-align:center;">0− </td> <td style="text-align:center;"><a href="/wiki/List_of_mesons#Notes_on_neutral_kaons" title="List of mesons">[*]</a> </td> <td style="text-align:center;">0 </td> <td style="text-align:center;">0 </td> <td style="text-align:right;">(5.116±0.021)×10−8 </td> <td style="text-align:left;"><a href="/wiki/Pion" title="Pion"> π± </a> + <a href="/wiki/Electron" title="Electron"> e∓ </a> + <a href="/wiki/Electron_neutrino" title="Electron neutrino"> ν e</a> or <a href="/wiki/Pion" title="Pion"> π± </a> + <a href="/wiki/Muon" title="Muon"> μ∓ </a> + <a href="/wiki/Muon_neutrino" title="Muon neutrino"> ν μ</a> or <a href="/wiki/Pion" title="Pion"> π0 </a> + <a href="/wiki/Pion" title="Pion"> π0 </a> + <a href="/wiki/Pion" title="Pion"> π0 </a> or <a href="/wiki/Pion" title="Pion"> π+ </a> + <a href="/wiki/Pion" title="Pion"> π0 </a> + <a href="/wiki/Pion" title="Pion"> π− </a> </td></tr></tbody></table> <figure typeof="mw:File/Thumb"><a href="/wiki/File:Quark_structure_kaon_plus.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Quark_structure_kaon_plus.svg/150px-Quark_structure_kaon_plus.svg.png" decoding="async" width="150" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Quark_structure_kaon_plus.svg/225px-Quark_structure_kaon_plus.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/2/2b/Quark_structure_kaon_plus.svg/300px-Quark_structure_kaon_plus.svg.png 2x" data-file-width="525" data-file-height="525" /></a><figcaption>Quark structure of the kaon (K+).</figcaption></figure> [*] See <a href="/wiki/List_of_mesons#Notes_on_neutral_kaons" title="List of mesons">Notes on neutral kaons</a> in the article <a href="/wiki/List_of_mesons" title="List of mesons">List of mesons</a>, and <a href="#Neutral_kaon_mixing">neutral kaon mixing</a>, below. [§]<style data-mw-deduplicate="TemplateStyles:r1041539562">.mw-parser-output .citation{word-wrap:break-word}.mw-parser-output .citation:target{background-color:rgba(0,127,255,0.133)}</style><a href="#ref_strongforce">^</a> <a href="/wiki/Strong_force" class="mw-redirect" title="Strong force">Strong</a> <a href="/wiki/Eigenstate" class="mw-redirect" title="Eigenstate">eigenstate</a>. No definite lifetime (see <a href="#Neutral_kaon_mixing">neutral kaon mixing</a>). [†]<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1041539562"><a href="#ref_Kaon">^</a> <a href="/wiki/Weak_force" class="mw-redirect" title="Weak force">Weak</a> <a href="/wiki/Eigenstate" class="mw-redirect" title="Eigenstate">eigenstate</a>. Makeup is missing small <a href="/wiki/CP_violation" title="CP violation">CP–violating</a> term (see <a href="#Neutral_kaon_mixing">neutral kaon mixing</a>). [‡]<link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1041539562"><a href="#ref_Kaonmass">^</a> The mass of the K0 L and K0 S are given as that of the K0 . However, it is known that a relatively minute difference between the masses of the K0 L and K0 S on the order of 3.5×10−6 eV/c2 exists.<a href="#cite_note-PDGK-long-7">[6]</a> Although the K0 and its antiparticle K0 are usually produced via the <a href="/wiki/Strong_force" class="mw-redirect" title="Strong force">strong force</a>, they decay <a href="/wiki/Weak_force" class="mw-redirect" title="Weak force">weakly</a>. Thus, once created the two are better thought of as superpositions of two weak <a href="/wiki/Eigenstate" class="mw-redirect" title="Eigenstate">eigenstates</a> which have vastly different lifetimes: <ul><li>The long-lived neutral kaon is called the K L ("K-long"), decays primarily into three <a href="/wiki/Pion" title="Pion">pions</a>, and has a mean lifetime of 5.18×10−8 s.</li> <li>The short-lived neutral kaon is called the K S ("K-short"), decays primarily into two pions, and has a mean lifetime 8.958×10−11 s.<figure typeof="mw:File/Thumb"><a href="/wiki/File:Quark_structure_antikaon.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/0/02/Quark_structure_antikaon.svg/150px-Quark_structure_antikaon.svg.png" decoding="async" width="150" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/0/02/Quark_structure_antikaon.svg/225px-Quark_structure_antikaon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/0/02/Quark_structure_antikaon.svg/300px-Quark_structure_antikaon.svg.png 2x" data-file-width="625" data-file-height="625" /></a><figcaption>Quark structure of the antikaon (K−).</figcaption></figure></li></ul> (See discussion of <a href="#Neutral_kaon_mixing">neutral kaon mixing</a> below.) An experimental observation made in 1964 that K-longs rarely decay into two pions was the discovery of <a href="/wiki/CP_violation" title="CP violation">CP violation</a> (see below). Main decay modes for K+ : <dl><dd><figure typeof="mw:File/Thumb"><a href="/wiki/File:Quark_structure_neutral_kaon.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Quark_structure_neutral_kaon.svg/150px-Quark_structure_neutral_kaon.svg.png" decoding="async" width="150" height="150" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Quark_structure_neutral_kaon.svg/225px-Quark_structure_neutral_kaon.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/c/c2/Quark_structure_neutral_kaon.svg/300px-Quark_structure_neutral_kaon.svg.png 2x" data-file-width="625" data-file-height="625" /></a><figcaption>Quark structure of the neutral kaon (K0).</figcaption></figure></dd></dl> <table class="wikitable sortable"> <tbody><tr> <th>Results </th> <th>Mode </th> <th><a href="/wiki/Branching_ratio" class="mw-redirect" title="Branching ratio">Branching ratio</a> </th></tr> <tr style="height: 2em;"> <td> μ+ ν μ </td> <td>leptonic </td> <td style="text-align:right;">63.55±0.11% </td></tr> <tr style="height: 2em;"> <td> π+ π0 </td> <td>hadronic </td> <td style="text-align:right;">20.66±0.08% </td></tr> <tr style="height: 2em;"> <td> π+ π+ π− </td> <td>hadronic </td> <td style="text-align:right;">5.59±0.04% </td></tr> <tr style="height: 2em;"> <td> π+ π0 π0 </td> <td>hadronic </td> <td style="text-align:right;">1.761±0.022% </td></tr> <tr style="height: 2em;"> <td> π0 e+ ν e </td> <td>semileptonic </td> <td style="text-align:right;">5.07±0.04% </td></tr> <tr style="height: 2em;"> <td> π0 μ+ ν μ </td> <td>semileptonic </td> <td style="text-align:right;">3.353±0.034% </td></tr></tbody></table> Decay modes for the K− are charge conjugates of the ones above. <div class="mw-heading mw-heading2"><h2 id="Parity_violation">Parity violation</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=2" title="Edit section: Parity violation">edit</a>]</div> Two different decays were found for charged strange mesons into <a href="/wiki/Pion" title="Pion">pions</a>: <dl><dd><table border="0"> <tbody><tr style="height: 2em;"> <td> Θ+ </td> <td>→</td> <td> π+ + π0 </td></tr> <tr style="height: 2em;"> <td> τ+ </td> <td>→</td> <td> π+ + π+ + π− </td></tr></tbody></table></dd></dl> The intrinsic <a href="/wiki/Parity_(physics)" title="Parity (physics)">parity</a> of the pion is P = −1 (since the pion is a bound state of a quark and an antiquark, which have opposite parities, with zero angular momentum), and parity is a multiplicative quantum number. Therefore, assuming the parent particle has zero spin, the two-pion and the three-pion final states have different parities (P = +1 and P = −1, respectively). It was thought that the initial states should also have different parities, and hence be two distinct particles. However, with increasingly precise measurements, no difference was found between the masses and lifetimes of each, respectively, indicating that they are the same particle. This was known as the τ–θ puzzle. It was resolved only by the discovery of <a href="/wiki/Parity_(physics)#Parity_violation" title="Parity (physics)">parity violation</a> in <a href="/wiki/Weak_interaction" title="Weak interaction">weak interactions</a> (most importantly, by the <a href="/wiki/Wu_experiment" title="Wu experiment">Wu experiment</a>). Since the mesons decay through weak interactions, parity is not conserved, and the two decays are actually decays of the same particle,<a href="#cite_note-Lee_1956-8">[7]</a> now called the K+ . <div class="mw-heading mw-heading2"><h2 id="History">History</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=3" title="Edit section: History">edit</a>]</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/Strangeness" title="Strangeness">Strangeness</a></div> <blockquote> The discovery of hadrons with the internal quantum number "strangeness" marks the beginning of a most exciting epoch in particle physics that even now, fifty years later, has not yet found its conclusion ... by and large experiments have driven the development, and that major discoveries came unexpectedly or even against expectations expressed by theorists.  — Bigi & Sanda (2016)<a href="#cite_note-9">[8]</a></blockquote> While looking for the hypothetical <a href="/wiki/Meson#History" title="Meson">nuclear meson</a>, <a href="/wiki/Louis_Leprince-Ringuet" title="Louis Leprince-Ringuet">Louis Leprince-Ringuet</a> found evidence for the existence of a positively charged heavier particle in 1944.<a href="#cite_note-:0-10">[9]</a><a href="#cite_note-:1-11">[10]</a> In 1947, <a href="/wiki/George_Rochester" title="George Rochester">G.D. Rochester</a> and <a href="/wiki/Clifford_Charles_Butler" title="Clifford Charles Butler">C.C. Butler</a> of the <a href="/wiki/University_of_Manchester" title="University of Manchester">University of Manchester</a> published two <a href="/wiki/Cloud_chamber" title="Cloud chamber">cloud chamber</a> photographs of <a href="/wiki/Cosmic_ray" title="Cosmic ray">cosmic ray</a>-induced events, one showing what appeared to be a neutral particle decaying into two charged pions, and one which appeared to be a charged particle decaying into a charged pion and something neutral. The estimated mass of the new particles was very rough, about half a proton's mass. More examples of these "V-particles" were slow in coming. <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:The_%22k_track_plate%22_showing_three-pion_decay_mode_of_a_kaon,_15_Jan_1949.png" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/f/f1/The_%22k_track_plate%22_showing_three-pion_decay_mode_of_a_kaon%2C_15_Jan_1949.png/220px-The_%22k_track_plate%22_showing_three-pion_decay_mode_of_a_kaon%2C_15_Jan_1949.png" decoding="async" width="220" height="95" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/f/f1/The_%22k_track_plate%22_showing_three-pion_decay_mode_of_a_kaon%2C_15_Jan_1949.png/330px-The_%22k_track_plate%22_showing_three-pion_decay_mode_of_a_kaon%2C_15_Jan_1949.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/f/f1/The_%22k_track_plate%22_showing_three-pion_decay_mode_of_a_kaon%2C_15_Jan_1949.png/440px-The_%22k_track_plate%22_showing_three-pion_decay_mode_of_a_kaon%2C_15_Jan_1949.png 2x" data-file-width="1098" data-file-height="473" /></a><figcaption>The "k track plate" showing the three-pion decay mode of a kaon. The kaon enters from the left, and decays at the point labelled A</figcaption></figure> In 1949, <a href="/wiki/Rosemary_Fowler" title="Rosemary Fowler">Rosemary Brown</a> (later Rosemary Fowler), a research student of <a href="/wiki/C._F._Powell" title="C. F. Powell">Cecil Powell</a> of the <a href="/wiki/University_of_Bristol" title="University of Bristol">University of Bristol</a>, spotted her 'k' track, made by a particle of very similar mass that decayed to three pions.<a href="#cite_note-:2-12">[11]</a><a href="#cite_note-Brown-Camerini-etal-1949-13">[12]</a>(p82) <blockquote> I knew at once that it was new and would be very important. We were seeing things that hadn't been seen before - that's what research in particle physics was. It was very exciting. — Fowler (2024)<a href="#cite_note-:2-12">[11]</a></blockquote> This led to the so-called 'tau–theta' problem:<a href="#cite_note-Sheehy2024-14">[13]</a> what seemed to be the same particle (now called K+ ) decayed in two different modes, Theta to two pions (parity +1), Tau to three pions (parity −1).<a href="#cite_note-Brown-Camerini-etal-1949-13">[12]</a> The solution to this puzzle turned out to be that weak interactions <a href="/wiki/Parity_violation" class="mw-redirect" title="Parity violation">do not conserve parity</a>.<a href="#cite_note-Lee_1956-8">[7]</a> The first breakthrough was obtained at <a href="/wiki/California_Institute_of_Technology" title="California Institute of Technology">Caltech</a>, where a cloud chamber was taken up <a href="/wiki/Mount_Wilson_(California)" title="Mount Wilson (California)">Mount Wilson</a>, for greater cosmic ray exposure. In 1950, 30 charged and 4 neutral "V-particles" were reported. Inspired by this, numerous mountaintop observations were made over the next several years, and by 1953, the following terminology was being used: "L meson" for either a <a href="/wiki/Muon" title="Muon">muon</a> or charged <a href="/wiki/Pion" title="Pion">pion</a>; "K meson" meant a particle intermediate in mass between the pion and <a href="/wiki/Nucleon" title="Nucleon">nucleon</a>. Leprince-Rinquet coined the still-used term "<a href="/wiki/Hyperon" title="Hyperon">hyperon</a>" to mean any particle heavier than a nucleon.<a href="#cite_note-:0-10">[9]</a><a href="#cite_note-:1-11">[10]</a> The Leprince-Ringuet particle turned out to be the K+ meson.<a href="#cite_note-:0-10">[9]</a><a href="#cite_note-:1-11">[10]</a> The decays were extremely slow; typical lifetimes are of the order of 10−10 s. However, production in <a href="/wiki/Pion" title="Pion">pion</a>–<a href="/wiki/Proton" title="Proton">proton</a> reactions proceeds much faster, with a time scale of 10−23 s. The problem of this mismatch was solved by <a href="/wiki/Abraham_Pais" title="Abraham Pais">Abraham Pais</a> who postulated the new quantum number called "<a href="/wiki/Strangeness_(particle_physics)" class="mw-redirect" title="Strangeness (particle physics)">strangeness</a>" which is conserved in <a href="/wiki/Strong_interaction" title="Strong interaction">strong interactions</a> but violated by the <a href="/wiki/Weak_interaction" title="Weak interaction">weak interactions</a>. <a href="/wiki/Strange_particle" title="Strange particle">Strange particles</a> appear copiously due to "associated production" of a strange and an antistrange particle together. It was soon shown that this could not be a <a href="/wiki/Multiplicative_quantum_number" title="Multiplicative quantum number">multiplicative quantum number</a>, because that would allow reactions which were never seen in the new <a href="/wiki/Synchrotron" title="Synchrotron">synchrotrons</a> which were commissioned in <a href="/wiki/Brookhaven_National_Laboratory" title="Brookhaven National Laboratory">Brookhaven National Laboratory</a> in 1953 and in the <a href="/wiki/Lawrence_Berkeley_Laboratory" class="mw-redirect" title="Lawrence Berkeley Laboratory">Lawrence Berkeley Laboratory</a> in 1955. <div class="mw-heading mw-heading2"><h2 id="CP_violation_in_neutral_meson_oscillations">CP violation in neutral meson oscillations</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=4" title="Edit section: CP violation in neutral meson oscillations">edit</a>]</div> Initially it was thought that although <a href="/wiki/Parity_(physics)" title="Parity (physics)">parity</a> was violated, <a href="/wiki/CP_symmetry" class="mw-redirect" title="CP symmetry">CP (charge parity) symmetry</a> was conserved. In order to understand the discovery of <a href="/wiki/CP_violation" title="CP violation">CP violation</a>, it is necessary to understand the mixing of neutral kaons; this phenomenon does not require CP violation, but it is the context in which CP violation was first observed. <div class="mw-heading mw-heading3"><h3 id="Neutral_kaon_mixing">Neutral kaon mixing</h3>[<a href="/w/index.php?title=Kaon&action=edit&section=5" title="Edit section: Neutral kaon mixing">edit</a>]</div> <figure class="mw-default-size" typeof="mw:File/Thumb"><a href="/wiki/File:Kaon-box-diagram-with-bar.svg" class="mw-file-description"><img src="//upload.wikimedia.org/wikipedia/commons/thumb/8/82/Kaon-box-diagram-with-bar.svg/220px-Kaon-box-diagram-with-bar.svg.png" decoding="async" width="220" height="183" class="mw-file-element" srcset="//upload.wikimedia.org/wikipedia/commons/thumb/8/82/Kaon-box-diagram-with-bar.svg/330px-Kaon-box-diagram-with-bar.svg.png 1.5x, //upload.wikimedia.org/wikipedia/commons/thumb/8/82/Kaon-box-diagram-with-bar.svg/440px-Kaon-box-diagram-with-bar.svg.png 2x" data-file-width="420" data-file-height="350" /></a><figcaption>Two different neutral K mesons, carrying different strangeness, can turn from one into another through the <a href="/wiki/Weak_interaction" title="Weak interaction">weak interactions</a>, since these interactions do not conserve strangeness. The strange quark in the anti- K0 turns into a down quark by successively absorbing two <a href="/wiki/W-boson" class="mw-redirect" title="W-boson">W-bosons</a> of opposite charge. The down antiquark in the anti- K0 turns into a strange antiquark by emitting them.</figcaption></figure> Since neutral kaons carry strangeness, they cannot be their own antiparticles. There must be then two different neutral kaons, differing by two units of strangeness. The question was then how to establish the presence of these two mesons. The solution used a phenomenon called <a href="/wiki/Neutral_particle_oscillations" class="mw-redirect" title="Neutral particle oscillations">neutral particle oscillations</a>, by which these two kinds of mesons can turn from one into another through the weak interactions, which cause them to decay into pions (see the adjacent figure). These oscillations were first investigated by <a href="/wiki/Murray_Gell-Mann" title="Murray Gell-Mann">Murray Gell-Mann</a> and <a href="/wiki/Abraham_Pais" title="Abraham Pais">Abraham Pais</a> together. They considered the CP-invariant time evolution of states with opposite strangeness. In matrix notation one can write <dl><dd><dl><dd><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \psi (t)=U(t)\psi (0)={\rm {e}}^{iHt}{\begin{pmatrix}a\\b\end{pmatrix}},\qquad H={\begin{pmatrix}M&\Delta \\\Delta &M\end{pmatrix}},}"> <semantics> <mrow class="MJX-TeXAtom-ORD"> <mstyle displaystyle="true" scriptlevel="0"> <mi>ψ</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mi>U</mi> <mo stretchy="false">(</mo> <mi>t</mi> <mo stretchy="false">)</mo> <mi>ψ</mi> <mo stretchy="false">(</mo> <mn>0</mn> <mo stretchy="false">)</mo> <mo>=</mo> <msup> <mrow class="MJX-TeXAtom-ORD"> <mrow class="MJX-TeXAtom-ORD"> <mi mathvariant="normal">e</mi> </mrow> </mrow> <mrow class="MJX-TeXAtom-ORD"> <mi>i</mi> <mi>H</mi> <mi>t</mi> </mrow> </msup> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>(</mo> <mtable rowspacing="4pt" columnspacing="1em"> <mtr> <mtd> <mi>a</mi> </mtd> </mtr> <mtr> <mtd> <mi>b</mi> </mtd> </mtr> </mtable> <mo>)</mo> </mrow> </mrow> <mo>,</mo> <mspace width="2em" /> <mi>H</mi> <mo>=</mo> <mrow class="MJX-TeXAtom-ORD"> <mrow> <mo>(</mo> <mtable rowspacing="4pt" columnspacing="1em"> <mtr> <mtd> <mi>M</mi> </mtd> <mtd> <mi mathvariant="normal">Δ</mi> </mtd> </mtr> <mtr> <mtd> <mi mathvariant="normal">Δ</mi> </mtd> <mtd> <mi>M</mi> </mtd> </mtr> </mtable> <mo>)</mo> </mrow> </mrow> <mo>,</mo> </mstyle> </mrow> <annotation encoding="application/x-tex">{\displaystyle \psi (t)=U(t)\psi (0)={\rm {e}}^{iHt}{\begin{pmatrix}a\\b\end{pmatrix}},\qquad H={\begin{pmatrix}M&\Delta \\\Delta &M\end{pmatrix}},}</annotation> </semantics> </math><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/cd817514c136a499f2c44ddbf9558f2929d8709f" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -2.505ex; width:51.431ex; height:6.176ex;" alt="{\displaystyle \psi (t)=U(t)\psi (0)={\rm {e}}^{iHt}{\begin{pmatrix}a\\b\end{pmatrix}},\qquad H={\begin{pmatrix}M&\Delta \\\Delta &M\end{pmatrix}},}"></dd></dl></dd></dl> where ψ is a <a href="/wiki/Quantum_state" title="Quantum state">quantum state</a> of the system specified by the amplitudes of being in each of the two <a href="/wiki/Quantum_mechanics#Basis_states" title="Quantum mechanics">basis states</a> (which are a and b at time t = 0). The diagonal elements (M) of the <a href="/wiki/Hamiltonian_(quantum_mechanics)" title="Hamiltonian (quantum mechanics)">Hamiltonian</a> are due to <a href="/wiki/Strong_interaction" title="Strong interaction">strong interaction</a> physics which conserves strangeness. The two diagonal elements must be equal, since the particle and antiparticle have equal masses in the absence of the weak interactions. The off-diagonal elements, which mix opposite strangeness particles, are due to <a href="/wiki/Weak_interactions" class="mw-redirect" title="Weak interactions">weak interactions</a>; <a href="/wiki/CP_symmetry" class="mw-redirect" title="CP symmetry">CP symmetry</a> requires them to be real. The consequence of the matrix H being real is that the probabilities of the two states will forever oscillate back and forth. However, if any part of the matrix were imaginary, as is forbidden by <a href="/wiki/CP_symmetry" class="mw-redirect" title="CP symmetry">CP symmetry</a>, then part of the combination will diminish over time. The diminishing part can be either one component (a) or the other (b), or a mixture of the two. <div class="mw-heading mw-heading4"><h4 id="Mixing">Mixing</h4>[<a href="/w/index.php?title=Kaon&action=edit&section=6" title="Edit section: Mixing">edit</a>]</div> The eigenstates are obtained by diagonalizing this matrix. This gives new eigenvectors, which we can call K1 which is the difference of the two states of opposite strangeness, and K2, which is the sum. The two are eigenstates of CP with opposite eigenvalues; K1 has CP = +1, and K2 has CP = −1 Since the two-pion final state also has CP = +1, only the K1 can decay this way. The K2 must decay into three pions. <a href="#cite_note-15">[14]</a> Since the mass of K2 is just a little larger than the sum of the masses of three pions, this decay proceeds very slowly, about 600 times slower than the decay of K1 into two pions. These two different modes of decay were observed by <a href="/wiki/Leon_Lederman" class="mw-redirect" title="Leon Lederman">Leon Lederman</a> and his coworkers in 1956, establishing the existence of the two <a href="/wiki/Weak_interaction" title="Weak interaction">weak</a> <a href="/wiki/Eigenstate" class="mw-redirect" title="Eigenstate">eigenstates</a> (states with definite <a href="/wiki/Mean_lifetime" class="mw-redirect" title="Mean lifetime">lifetimes</a> under decays via the <a href="/wiki/Weak_force" class="mw-redirect" title="Weak force">weak force</a>) of the neutral kaons. These two weak eigenstates are called the K L (K-long, τ) and K S (K-short, θ). <a href="/wiki/CP_symmetry" class="mw-redirect" title="CP symmetry">CP symmetry</a>, which was assumed at the time, implies that K S = K1 and K L = K2. <div class="mw-heading mw-heading4"><h4 id="Oscillation">Oscillation</h4>[<a href="/w/index.php?title=Kaon&action=edit&section=7" title="Edit section: Oscillation">edit</a>]</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/Neutral_particle_oscillation" title="Neutral particle oscillation">Neutral particle oscillation</a></div> An initially pure beam of K0 will turn into its antiparticle, K0 , while propagating, which will turn back into the original particle, K0 , and so on. This is called particle oscillation. On observing the weak decay into leptons, it was found that a K0 always decayed into a positron, whereas the antiparticle K0 decayed into the electron. The earlier analysis yielded a relation between the rate of electron and positron production from sources of pure K0 and its antiparticle K0 . Analysis of the time dependence of this <a href="/wiki/Semileptonic_decay" title="Semileptonic decay">semileptonic decay</a> showed the phenomenon of oscillation, and allowed the extraction of the mass splitting between the K S and K L. Since this is due to weak interactions it is very small, 10−15 times the mass of each state, namely ∆MK = M(KL) − M(KS) = 3.484(6)×10−12 MeV .<a href="#cite_note-16">[15]</a> <div class="mw-heading mw-heading4"><h4 id="Regeneration">Regeneration</h4>[<a href="/w/index.php?title=Kaon&action=edit&section=8" title="Edit section: Regeneration">edit</a>]</div> A beam of neutral kaons decays in flight so that the short-lived K S disappears, leaving a beam of pure long-lived K L. If this beam is shot into matter, then the K0 and its antiparticle K0 interact differently with the nuclei. The K0 undergoes quasi-<a href="/wiki/Elastic_scattering" title="Elastic scattering">elastic scattering</a> with <a href="/wiki/Nucleon" title="Nucleon">nucleons</a>, whereas its antiparticle can create <a href="/wiki/Hyperon" title="Hyperon">hyperons</a>. <a href="/wiki/Quantum_coherence" class="mw-redirect" title="Quantum coherence">Quantum coherence</a> between the two particles is lost due to the different interactions that the two components separately engage in. The emerging beam then contains different linear superpositions of the K0 and K0 . Such a superposition is a mixture of K L and K S; the K S is regenerated by passing a neutral kaon beam through matter.<a href="#cite_note-17">[16]</a> Regeneration was observed by <a href="/wiki/Oreste_Piccioni" title="Oreste Piccioni">Oreste Piccioni</a> and his collaborators at <a href="/wiki/Lawrence_Berkeley_National_Laboratory" title="Lawrence Berkeley National Laboratory">Lawrence Berkeley National Laboratory</a>.<a href="#cite_note-18">[17]</a> Soon thereafter, Robert Adair and his coworkers reported excess K S regeneration, thus opening a new chapter in this history. <div class="mw-heading mw-heading3"><h3 id="CP_violation">CP violation</h3>[<a href="/w/index.php?title=Kaon&action=edit&section=9" title="Edit section: CP violation">edit</a>]</div> While trying to verify Adair's results, J. Christenson, <a href="/wiki/James_Cronin" title="James Cronin">James Cronin</a>, <a href="/wiki/Val_Fitch" class="mw-redirect" title="Val Fitch">Val Fitch</a> and <a href="/wiki/Rene_Turlay" class="mw-redirect" title="Rene Turlay">Rene Turlay</a> of <a href="/wiki/Princeton_University" title="Princeton University">Princeton University</a> found decays of K L into two pions (CP = +1) in an <a href="/wiki/Fitch%E2%80%93Cronin_experiment" class="mw-redirect" title="Fitch–Cronin experiment">experiment performed in 1964</a> at the <a href="/wiki/Alternating_Gradient_Synchrotron" title="Alternating Gradient Synchrotron">Alternating Gradient Synchrotron</a> at the <a href="/wiki/Brookhaven_National_Laboratory" title="Brookhaven National Laboratory">Brookhaven laboratory</a>.<a href="#cite_note-19">[18]</a> As explained in <a href="#Mixing">an earlier section</a>, this required the assumed initial and final states to have different values of CP, and hence immediately suggested <a href="/wiki/CP_violation" title="CP violation">CP violation</a>. Alternative explanations such as nonlinear quantum mechanics and a new unobserved particle (<a href="/wiki/Hyperphoton" title="Hyperphoton">hyperphoton</a>) were soon ruled out, leaving CP violation as the only possibility. Cronin and Fitch received the <a href="/wiki/Nobel_Prize_in_Physics" title="Nobel Prize in Physics">Nobel Prize in Physics</a> for this discovery in 1980. It turns out that although the K L and K S are <a href="/wiki/Weak_interaction" title="Weak interaction">weak</a> <a href="/wiki/Eigenstates" class="mw-redirect" title="Eigenstates">eigenstates</a> (because they have definite <a href="/wiki/Mean_lifetime" class="mw-redirect" title="Mean lifetime">lifetimes</a> for decay by way of the weak force), they are not quite CP eigenstates. Instead, for small ε (and up to normalization), <dl><dd> K L = K2 + εK1</dd></dl> and similarly for K S. Thus occasionally the K L decays as a K1 with CP = +1, and likewise the K S can decay with CP = −1. This is known as indirect CP violation, CP violation due to mixing of K0 and its antiparticle. There is also a direct CP violation effect, in which the CP violation occurs during the decay itself. Both are present, because both mixing and decay arise from the same interaction with the <a href="/wiki/W_boson" class="mw-redirect" title="W boson">W boson</a> and thus have CP violation predicted by the <a href="/wiki/CKM_matrix" class="mw-redirect" title="CKM matrix">CKM matrix</a>. Direct CP violation was discovered in the kaon decays in the early 2000s by the <a href="/wiki/NA48" class="mw-redirect" title="NA48">NA48</a> and <a href="/w/index.php?title=KTeV&action=edit&redlink=1" class="new" title="KTeV (page does not exist)">KTeV</a> experiments at CERN and Fermilab.<a href="#cite_note-20">[19]</a> <div class="mw-heading mw-heading2"><h2 id="See_also">See also</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=10" title="Edit section: See also">edit</a>]</div> <ul><li><a href="/wiki/Hadron" title="Hadron">Hadrons</a>, <a href="/wiki/Meson" title="Meson">mesons</a>, <a href="/wiki/Hyperon" title="Hyperon">hyperons</a> and <a href="/wiki/Flavour_(particle_physics)" title="Flavour (particle physics)">flavour</a></li> <li><a href="/wiki/Strange_quark" title="Strange quark">Strange quark</a> and the <a href="/wiki/Quark_model" title="Quark model">quark model</a></li> <li><a href="/wiki/Parity_(physics)" title="Parity (physics)">Parity (physics)</a>, <a href="/wiki/Charge_conjugation" class="mw-redirect" title="Charge conjugation">charge conjugation</a>, <a href="/wiki/T-symmetry" title="T-symmetry">time reversal symmetry</a>, <a href="/wiki/CPT_invariance" class="mw-redirect" title="CPT invariance">CPT invariance</a> and <a href="/wiki/CP_violation" title="CP violation">CP violation</a></li> <li><a href="/wiki/Neutrino_oscillation" title="Neutrino oscillation">Neutrino oscillation</a></li> <li><a href="/wiki/Neutral_particle_oscillation" title="Neutral particle oscillation">Neutral particle oscillation</a></li></ul> <div class="mw-heading mw-heading2"><h2 id="Footnotes">Footnotes</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=11" title="Edit section: Footnotes">edit</a>]</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 reflist-lower-alpha"> <ol class="references"> <li id="cite_note-1"><a href="#cite_ref-1">^</a> Until the 1960s the positively charged kaon was formerly called τ+ or θ+, as it was believed to be two different particles. See the <a href="#Parity_violation">§ Parity violation</a>. </li> </ol></div> <div class="mw-heading mw-heading2"><h2 id="References">References</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=12" title="Edit section: References">edit</a>]</div> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1239543626"><div class="reflist reflist-columns references-column-width" style="column-width: 40em;"> <ol class="references"> <li id="cite_note-PDGKaon-2"><a href="#cite_ref-PDGKaon_2-0">^</a> <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 .citation:target{background-color:rgba(0,127,255,0.133)}.mw-parser-output .id-lock-free.id-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/6/65/Lock-green.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-limited.id-lock-limited a,.mw-parser-output .id-lock-registration.id-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/d/d6/Lock-gray-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .id-lock-subscription.id-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/a/aa/Lock-red-alt-2.svg")right 0.1em center/9px no-repeat}.mw-parser-output .cs1-ws-icon a{background:url("//upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg")right 0.1em center/12px no-repeat}body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-free a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .id-lock-limited a,body:not(.skin-timeless):not(.skin-minerva) .mw-parser-output .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 id="CITEREFZyla,_P.A.2020" class="citation web cs1">Zyla, P.A.; et al. (2020). <a rel="nofollow" class="external text" href="http://pdg.lbl.gov/2021/listings/rpp2021-list-K-plus-minus.pdf">"Particle listings – K± "</a> (PDF).</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=unknown&rft.btitle=Particle+listings+%E2%80%93+%3Cspan+style%3D%22white-space%3Anowrap%3B%22%3E%3Cspan+class%3D%22nowrap%22%3E%3Cspan+style%3D%22display%3Ainline-block%3Bmargin-bottom%3A-0.3em%3Bvertical-align%3A0.8em%3Bline-height%3A1.0em%3Bfont-size%3A80%25%3Btext-align%3Aright%22%3E%3Csup+style%3D%22font-size%3Ainherit%3Bline-height%3Ainherit%3Bvertical-align%3Abaseline%22%3E%3C%2Fsup%3E%3Cbr+%2F%3E%3Csub+style%3D%22font-size%3Ainherit%3Bline-height%3Ainherit%3Bvertical-align%3Abaseline%22%3E%3C%2Fsub%3E%3C%2Fspan%3E%3C%2Fspan%3EK%3Cspan+class%3D%22nowrap%22%3E%3Cspan+style%3D%22display%3Ainline-block%3Bmargin-bottom%3A-0.3em%3Bvertical-align%3A0.8em%3Bline-height%3A1.0em%3Bfont-size%3A80%25%3Btext-align%3Aleft%22%3E%3Csup+style%3D%22font-size%3Ainherit%3Bline-height%3Ainherit%3Bvertical-align%3Abaseline%22%3E%26plusmn%3B%3C%2Fsup%3E%3Cbr+%2F%3E%3Csub+style%3D%22font-size%3Ainherit%3Bline-height%3Ainherit%3Bvertical-align%3Abaseline%22%3E%3C%2Fsub%3E%3C%2Fspan%3E%3C%2Fspan%3E%3C%2Fspan%3E&rft.date=2020&rft.au=Zyla%2C+P.A.&rft_id=http%3A%2F%2Fpdg.lbl.gov%2F2021%2Flistings%2Frpp2021-list-K-plus-minus.pdf&rfr_id=info%3Asid%2Fen.wikipedia.org%3AKaon" class="Z3988"> </li> <li id="cite_note-PDGKaon0-3"><a href="#cite_ref-PDGKaon0_3-0">^</a> <link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFZyla,_P.A.2020" class="citation web cs1">Zyla, P.A.; et al. 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"Review of Particle Physics". <a href="/wiki/Physics_Letters_B" class="mw-redirect" title="Physics Letters B">Physics Letters B</a>. 592 (1): 1. <a href="/wiki/ArXiv_(identifier)" class="mw-redirect" title="ArXiv (identifier)">arXiv</a>:<a rel="nofollow" class="external text" href="https://arxiv.org/abs/astro-ph/0406663">astro-ph/0406663</a>. <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/2004PhLB..592....1P">2004PhLB..592....1P</a>. <a href="/wiki/Doi_(identifier)" class="mw-redirect" title="Doi (identifier)">doi</a>:<a rel="nofollow" class="external text" href="https://doi.org/10.1016%2Fj.physletb.2004.06.001">10.1016/j.physletb.2004.06.001</a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Ajournal&rft.genre=article&rft.jtitle=Physics+Letters+B&rft.atitle=Review+of+Particle+Physics&rft.volume=592&rft.issue=1&rft.pages=1&rft.date=2004&rft_id=info%3Aarxiv%2Fastro-ph%2F0406663&rft_id=info%3Adoi%2F10.1016%2Fj.physletb.2004.06.001&rft_id=info%3Abibcode%2F2004PhLB..592....1P&rft.aulast=Eidelman&rft.aufirst=S.&rft.au=Hayes%2C+K.G.&rft.au=Olive%2C+K.A.&rft.au=Aguilar-Benitez%2C+M.&rft.au=Amsler%2C+C.&rft.au=Asner%2C+D.&rft.au=Babu%2C+K.S.&rft.au=Barnett%2C+R.M.&rft.au=Beringer%2C+J.&rft.au=Burchat%2C+P.R.&rft.au=Carone%2C+C.D.&rft.au=Caso%2C+S.&rft.au=Conforto%2C+G.&rft.au=Dahl%2C+O.&rft.au=d%27Ambrosio%2C+G.&rft.au=Doser%2C+M.&rft.au=Feng%2C+J.+L.&rft.au=Gherghetta%2C+T.&rft.au=Gibbons%2C+L.&rft.au=Goodman%2C+M.&rft.au=Grab%2C+C.&rft.au=Groom%2C+D.E.&rft.au=Gurtu%2C+A.&rft.au=Hagiwara%2C+K.&rft.au=Hern%C3%A1ndez-Rey%2C+J.J.&rft.au=Hikasa%2C+K.&rft.au=Honscheid%2C+K.&rft.au=Jawahery%2C+H.&rft.au=Kolda%2C+C.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AKaon" class="Z3988"></li> <li>The quark model, by J.J.J. Kokkedee [<a href="/wiki/Wikipedia:Citing_sources#What_information_to_include" title="Wikipedia:Citing sources">full citation needed</a>]</li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFSozzi2008" class="citation book cs1">Sozzi, M.S. (2008). Discrete symmetries and CP violation. <a href="/wiki/Oxford_University_Press" title="Oxford University Press">Oxford University Press</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/978-0-19-929666-8" title="Special:BookSources/978-0-19-929666-8"><bdi>978-0-19-929666-8</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Discrete+symmetries+and+CP+violation&rft.pub=Oxford+University+Press&rft.date=2008&rft.isbn=978-0-19-929666-8&rft.aulast=Sozzi&rft.aufirst=M.S.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AKaon" class="Z3988"></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFBigiSanda2000" class="citation book cs1">Bigi, I. I.; Sanda, A.I. (2000). CP violation. <a href="/wiki/Cambridge_University_Press" title="Cambridge University Press">Cambridge University Press</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-521-44349-0" title="Special:BookSources/0-521-44349-0"><bdi>0-521-44349-0</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=CP+violation&rft.pub=Cambridge+University+Press&rft.date=2000&rft.isbn=0-521-44349-0&rft.aulast=Bigi&rft.aufirst=I.+I.&rft.au=Sanda%2C+A.I.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AKaon" class="Z3988"></li> <li><link rel="mw-deduplicated-inline-style" href="mw-data:TemplateStyles:r1238218222"><cite id="CITEREFGriffiths1987" class="citation book cs1">Griffiths, D. J. (1987). Introduction to Elementary Particle. <a href="/wiki/John_Wiley_%26_Sons" class="mw-redirect" title="John Wiley & Sons">John Wiley & Sons</a>. <a href="/wiki/ISBN_(identifier)" class="mw-redirect" title="ISBN (identifier)">ISBN</a> <a href="/wiki/Special:BookSources/0-471-60386-4" title="Special:BookSources/0-471-60386-4"><bdi>0-471-60386-4</bdi></a>.</cite><span title="ctx_ver=Z39.88-2004&rft_val_fmt=info%3Aofi%2Ffmt%3Akev%3Amtx%3Abook&rft.genre=book&rft.btitle=Introduction+to+Elementary+Particle&rft.pub=John+Wiley+%26+Sons&rft.date=1987&rft.isbn=0-471-60386-4&rft.aulast=Griffiths&rft.aufirst=D.+J.&rfr_id=info%3Asid%2Fen.wikipedia.org%3AKaon" class="Z3988"></li></ul> <div class="mw-heading mw-heading2"><h2 id="External_links">External links</h2>[<a href="/w/index.php?title=Kaon&action=edit&section=14" title="Edit section: External links">edit</a>]</div> <style data-mw-deduplicate="TemplateStyles:r1235681985">.mw-parser-output .side-box{margin:4px 0;box-sizing:border-box;border:1px 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title="Top quark">Top (quark</a></li> <li><a href="/wiki/Top_antiquark" class="mw-redirect" title="Top antiquark">antiquark)</a></li> <li><a href="/wiki/Bottom_quark" title="Bottom quark">Bottom (quark</a></li> <li><a href="/wiki/Bottom_antiquark" class="mw-redirect" title="Bottom antiquark">antiquark)</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;font-weight:normal;"><a href="/wiki/Lepton" title="Lepton">Leptons</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/Electron" title="Electron">Electron</a></li> <li><a href="/wiki/Positron" title="Positron">Positron</a></li> <li><a href="/wiki/Muon" title="Muon">Muon</a></li> <li><a href="/wiki/Muon" title="Muon">Antimuon</a></li> <li><a href="/wiki/Tau_(particle)" title="Tau (particle)">Tau</a></li> <li><a href="/wiki/Tau_(particle)" title="Tau (particle)">Antitau</a></li> <li><a href="/wiki/Neutrino" title="Neutrino">Neutrino</a> <ul><li><a href="/wiki/Electron_neutrino" title="Electron neutrino">Electron neutrino</a></li> <li><a href="/wiki/Neutrino#Antineutrinos" title="Neutrino">Electron antineutrino</a></li> <li><a href="/wiki/Muon_neutrino" title="Muon neutrino">Muon neutrino</a></li> <li><a href="/wiki/Neutrino#Antineutrinos" title="Neutrino">Muon antineutrino</a></li> <li><a href="/wiki/Tau_neutrino" title="Tau neutrino">Tau neutrino</a></li> <li><a href="/wiki/Neutrino#Antineutrinos" title="Neutrino">Tau antineutrino</a></li></ul></li></ul> </div></td></tr></tbody></table><div></div></td></tr><tr><th scope="row" class="navbox-group" style="width:1%;text-align: center;"><a href="/wiki/Boson" title="Boson">Bosons</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:4em;font-weight:normal; text-align: center;"><a href="/wiki/Gauge_boson" title="Gauge boson">Gauge</a></th><td class="navbox-list-with-group navbox-list navbox-odd" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Photon" title="Photon">Photon</a></li> <li><a href="/wiki/Gluon" title="Gluon">Gluon</a></li> <li><a href="/wiki/W_and_Z_bosons" title="W and Z bosons">W and Z bosons</a></li></ul> </div></td></tr><tr><th scope="row" class="navbox-group" style="width:4em;font-weight:normal; text-align: center;"><a href="/wiki/Scalar_boson" title="Scalar boson">Scalar</a></th><td class="navbox-list-with-group navbox-list navbox-even" style="padding:0"><div style="padding:0 0.25em"> <ul><li><a href="/wiki/Higgs_boson" title="Higgs boson">Higgs boson </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;"><a href="/wiki/Ghost_(physics)" title="Ghost (physics)">Ghost fields</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/Faddeev%E2%80%93Popov_ghost" title="Faddeev–Popov ghost">Faddeev–Popov ghosts</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><th scope="row" class="navbox-group" style="width:1%;font-weight:normal; text-align: center;"><a href="/wiki/Superpartner" title="Superpartner">Superpartners</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/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 class="mw-selflink selflink">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 href="/wiki/Mathematical_formulation_of_the_Standard_Model" title="Mathematical formulation of the Standard Model">mathematical formulation</a></li></ul></li> <li><a href="/wiki/Subatomic_particle" title="Subatomic particle">Subatomic particles</a></li> <li><a href="/wiki/Particle" title="Particle">Particles</a></li> <li><a href="/wiki/Antiparticle" title="Antiparticle">Antiparticles</a></li> <li><a href="/wiki/Nuclear_physics" title="Nuclear physics">Nuclear physics</a></li> <li><a href="/wiki/Eightfold_way_(physics)" title="Eightfold way (physics)">Eightfold way</a> <ul><li><a href="/wiki/Quark_model" title="Quark model">Quark model</a></li></ul></li> <li><a href="/wiki/Exotic_matter" title="Exotic matter">Exotic matter</a></li> <li><a href="/wiki/Massless_particle" title="Massless particle">Massless particle</a></li> <li><a href="/wiki/Relativistic_particle" title="Relativistic particle">Relativistic particle</a></li> <li><a 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