Flash-1: Measurement of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs in non-ultra peripheral Pb+Pb collisions with the ATLAS detector

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The $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs are identified via selections on pair momentum asymmetry and acoplanarity, and the contribution from the heavy flavor decay background is estimated using both template and asymptotic fit methods. The pair yields are measured differentially as functions of the centrality, average transverse-momentum, ($p_{T}$) and rapidity of the pair. The measurement shows a depletion in the number of muon pairs near-zero acoplanarity in central events, resulting in the distributions peaking at non-zero values of acoplanarity. Fits to the perpendicular transverse momentum ($k_{\perp}$) distributions are used to estimate the centrality dependence of this peak position. The most probable is shown to increase from the most peripheral to the most central collisions, reaching a value of $k_{\perp} = 36 \pm 1$ MeV in the 0-5\% most-central collisions. The ability of these measurements to qualitatively differentiate between different physical origins of the observed centrality and $p_{T}$ dependence, including comparisons to several theoretical calculations, are discussed. Gilbert, Benjamin Jacob" /> <meta name="keywords" content="CERN Document Server, WebSearch, CERN Document Server" /> <script type="text/javascript" src="https://cds.cern.ch/js/jquery.min.js"></script>  <link rel="stylesheet" href="https://cds.cern.ch/img/webnews.css" type="text/css" />  <script type="text/javascript" src="https://cds.cern.ch/js/webnews.js?v=20131009"></script> <meta property="fb:app_id" content="137353533001720"/> <script type="text/x-mathjax-config"> MathJax.Hub.Config({ tex2jax: {inlineMath: [['$','$']], processEscapes: true}, showProcessingMessages: false, messageStyle: "none" }); </script> <script src="/MathJax/MathJax.js?config=TeX-AMS_CHTML" type="text/javascript"> </script>  <meta content="Flash-1: Measurement of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs in non-ultra peripheral Pb+Pb collisions with the ATLAS detector" name="citation_title" /> <meta content="2021/01/15" name="citation_publication_date" /> <meta name="citation_online_date" content="2021/01/20">  <meta content="Flash-1: Measurement of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs in non-ultra peripheral Pb+Pb collisions with the ATLAS detector" property="og:title" /> <meta content="Initial Stages 2021" property="og:title" /> <meta content="website" property="og:type" /> <meta content="website" property="og:type" /> <meta content="https://cds.cern.ch/record/2749845" property="og:url" /> <meta property="og:video:height" content="360" /> <meta property="og:video:width" content="640" /> <meta property="og:video" content="https://lecturemedia.cern.ch/2021/854124c237/854124c237-1000-kbps-853x480-25-fps-audio-96-kbps-44-kHz-stereo.mp4" /> <meta property="og:video:type" content="video/mp4" /> <meta property="og:image" content="https://lecturemedia.cern.ch/2021/854124c237/854124c237-posterframe-640x360-at-5.0-percent.jpg" /> <meta name="twitter:player:height" content="360" /> <meta name="twitter:player:width" content="640" /> <link rel="image_src" href="https://lecturemedia.cern.ch/2021/854124c237/854124c237-posterframe-640x360-at-5.0-percent.jpg" /> <link rel="video_src" href="https://cds.cern.ch/mediaplayer.swf?file=/854124c237/854124c237-1000-kbps-853x480-25-fps-audio-96-kbps-44-kHz-stereo.mp4&streamer=rtmp://wowza.cern.ch:1935/vod&provider=rtmp&stretching=exactfit&image=https://lecturemedia.cern.ch/2021/854124c237/854124c237-posterframe-640x360-at-5.0-percent.jpg"/> <meta name="twitter:player" content="https://cds.cern.ch/video/?"/> <meta content="CERN Document Server" property="og:site_name" /> <meta content="ATLAS measurements of dimuons produced via $\gamma\gamma$ scattering processes in inelastic, non-ultra-peripheral Pb+Pb collisions at 5.02 TeV are presented using an integrated luminosity of 1.9 nb$^{−1}$. The $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs are identified via selections on pair momentum asymmetry and acoplanarity, and the contribution from the heavy flavor decay background is estimated using both template and asymptotic fit methods. The pair yields are measured differentially as functions of the centrality, average transverse-momentum, ($p_{T}$) and rapidity of the pair. The measurement shows a depletion in the number of muon pairs near-zero acoplanarity in central events, resulting in the distributions peaking at non-zero values of acoplanarity. Fits to the perpendicular transverse momentum ($k_{\perp}$) distributions are used to estimate the centrality dependence of this peak position. The most probable is shown to increase from the most peripheral to the most central collisions, reaching a value of $k_{\perp} = 36 \pm 1$ MeV in the 0-5\% most-central collisions. The ability of these measurements to qualitatively differentiate between different physical origins of the observed centrality and $p_{T}$ dependence, including comparisons to several theoretical calculations, are discussed." property="og:description" />  <meta content="summary" name="twitter:card" /> <style></style> </head> <body class="CERN32Document32Server search" lang="en">  <div id="cern-toolbar"> <h1><a href="http://cern.ch" title="CERN">CERN <span>Accelerating science</span></a></h1> <ul> <li class="cern-accountlinks"><a class="cern-account" href="https://cds.cern.ch/youraccount/login?ln=en&referer=https%3A//cds.cern.ch/record/2749845" title="Sign in to your CERN account">Sign in</a></li> <li><a class="cern-directory" href="http://cern.ch/directory" title="Search CERN resources and browse the directory">Directory</a></li> </ul> </div>   <div role="banner" class="clearfix" id="header"> <div class="header-inner inner"> <hgroup class="clearfix"> <h2 id="site-name"> <a rel="home" title="Home" href="/"><span>CERN Document Server</span></a> </h2> <h3 id="site-slogan">Access articles, reports and multimedia content in HEP</h3> </hgroup> <div role="navigation" id="main-navigation" class="cdsmenu"> <h2 class="element-invisible">Main menu</h2><ul class="links inline clearfix"> <li class="menu-386 first active-trail"><a class="active-trail" href="https://cds.cern.ch/?ln=en">Search</a></li> <li class="menu-444 "><a class="" title="" href="https://cds.cern.ch/submit?ln=en">Submit</a></li> <li class="menu-426 "><a class="" href="https://cds.cern.ch/help/?ln=en">Help</a></li> <li class="leaf hassubcdsmenu"> <a hreflang="en" class="header" href="https://cds.cern.ch/youraccount/display?ln=en">Personalize</a> <ul class="subsubcdsmenu"><li><a href="https://cds.cern.ch/youralerts/list?ln=en">Your alerts</a></li><li><a href="https://cds.cern.ch/yourbaskets/display?ln=en">Your baskets</a></li><li><a href="https://cds.cern.ch/yourcomments?ln=en">Your comments</a></li><li><a href="https://cds.cern.ch/youralerts/display?ln=en">Your searches</a></li></ul></li> </ul> </div> </div> </div>  <table class="navtrailbox"> <tr> <td class="navtrailboxbody"> <a href="/?ln=en" class="navtrail">Home</a> > Flash-1: Measurement of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs in non-ultra peripheral Pb+Pb collisions with the ATLAS detector </td> </tr> </table> </div> <div class="pagebody"><div class="pagebodystripemiddle"> <div class="detailedrecordbox"> <div class="detailedrecordtabs"> <div> <ul class="detailedrecordtabs"><li class="on first"><a href="/record/2749845/?ln=en">Information </a></li><li class="disabled"><a>Files </a></li></ul> <div id="tabsSpacer" style="clear:both;height:0px"> </div></div> </div> <div class="detailedrecordboxcontent"> <div class="top-left-folded"></div> <div class="top-right-folded"></div> <div class="inside">  <abbr class="unapi-id" title="2749845"></abbr>  <link href="/img/download_and_embed_buttons.css" rel="stylesheet" type="text/css" /> <style type="text/css">  .video_talk_wrapper{ max-width: 640px; 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Geneva</td></tr>  <script type="text/javascript"> /* * Changes the Imprint title to Date - Duration as requested by RQF0820114 * This is a hack not to touch the general imprint format element */ $(document).ready(function() { var collections = 'Indico'; if (collections.indexOf('E-LEARNING') > -1) { $('.cern-imprint-label').text('Date - Duration'); } }) </script> <tr><td class="formatRecordLabel cern-imprint-label"> Imprint </td><td style="padding-left:5px;">2021-01-15. - 323.</td></tr>  <tr><td class="formatRecordLabel"> Series </td><td style="padding-left:5px;">(<a href="/search?f=490__a&p=Conferences">Conferences</a>)<br/>(<a href="/search?f=490__a&p=Initial%20Stages%202021">Initial Stages 2021</a>)</td></tr> <tr><td class="formatRecordLabel"> Lecture note </td><td style="padding-left:5px;"> on 2021-01-15T18:25:00<br/></td></tr> <tr><td class="formatRecordLabel"> Subject category </td><td style="padding-left:5px;">Conferences</td></tr> <tr><td class="formatRecordLabel"> Abstract </td><td style="padding-left:5px;">ATLAS measurements of dimuons produced via $\gamma\gamma$ scattering processes in inelastic, non-ultra-peripheral Pb+Pb collisions at 5.02 TeV are presented using an integrated luminosity of 1.9 nb$^{−1}$. The $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs are identified via selections on pair momentum asymmetry and acoplanarity, and the contribution from the heavy flavor decay background is estimated using both template and asymptotic fit methods. The pair yields are measured differentially as functions of the centrality, average transverse-momentum, ($p_{T}$) and rapidity of the pair. The measurement shows a depletion in the number of muon pairs near-zero acoplanarity in central events, resulting in the distributions peaking at non-zero values of acoplanarity. Fits to the perpendicular transverse momentum ($k_{\perp}$) distributions are used to estimate the centrality dependence of this peak position. The most probable is shown to increase from the most peripheral to the most central collisions, reaching a value of $k_{\perp} = 36 \pm 1$ MeV in the 0-5\% most-central collisions. The ability of these measurements to qualitatively differentiate between different physical origins of the observed centrality and $p_{T}$ dependence, including comparisons to several theoretical calculations, are discussed.</td></tr> <tr><td class="formatRecordLabel"> Copyright/License </td><td style="padding-left:5px;"><a href="https://copyright.web.cern.ch/">© 2021-2024 CERN</a></td></tr> <tr><td class="formatRecordLabel"> Submitted by </td><td style="padding-left:5px;"><a href="mailto:alexander.milov@cern.ch">alexander.milov@cern.ch</a></td></tr> </table> <br/><div><div style="clear: both;"> </div></div> <script type="text/javascript"> // Initially hide: $(".longCaption").hide(); // Allow to toggle visibility: $(".toggleLongCaption").toggle(function(){ $(this).siblings(".longCaption").show('fast'); var thisElem = $(this); thisElem.text(thisElem.text() === "more" ? 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The $\\gamma\\gamma \\rightarrow \\mu^{+}\\mu^{-}$ pairs are identified via selections on pair momentum asymmetry and acoplanarity, and the contribution from the heavy flavor decay background is estimated using both template and asymptotic fit methods. The pair yields are measured differentially as functions of the centrality, average transverse-momentum, ($p_{T}$) and rapidity of the pair. The measurement shows a depletion in the number of muon pairs near-zero acoplanarity in central events, resulting in the distributions peaking at non-zero values of acoplanarity. Fits to the perpendicular transverse momentum ($k_{\\perp}$) distributions are used to estimate the centrality dependence of this peak position. The most probable is shown to increase from the most peripheral to the most central collisions, reaching a value of $k_{\\perp} = 36 \\pm 1$ MeV in the 0-5\\% most-central collisions. 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Flash-1: Measurement of $\gamma\gamma \rightarrow \mu^{+}\mu^{-}$ pairs in non-ultra peripheral Pb+Pb collisions with the ATLAS detector - CERN Document Server