{"id":2986,"date":"2015-04-20T00:10:58","date_gmt":"2015-04-20T00:10:58","guid":{"rendered":"http:\/\/www.particlebites.com\/?p=2986"},"modified":"2015-04-20T00:10:58","modified_gmt":"2015-04-20T00:10:58","slug":"a-tau-neutrino-runs-into-a-candy-shop","status":"publish","type":"post","link":"https:\/\/www.particlebites.com\/?p=2986","title":{"rendered":"A Tau Neutrino Runs into a Candy Shop&#8230;"},"content":{"rendered":"<p>We\u00a0recently discussed some\u00a0<a href=\"http:\/\/www.particlebites.com\/?p=2925\">curiosities in the data from the IceCube neutrino detector<\/a>. This is a follow up Particle Bite on\u00a0some of the sugary\u00a0nomenclature IceCube uses to characterize some of its events.<\/p>\n<p>As we\u00a0explained previously, IceCube is a gigantic ultra-high energy cosmic neutrino detector\u00a0in Antarctica.\u00a0These neutrinos have energies between 10-100 times higher than the protons colliding at the Large Hadron Collider, and their origin and nature are largely a mystery.\u00a0One thing that\u00a0IceCube\u00a0can tell us about these neutrinos is their <a href=\"http:\/\/arxiv.org\/abs\/1502.03376\">flavor composition<\/a>; see e.g. this post for a <a href=\"http:\/\/www.quantumdiaries.org\/2010\/08\/02\/solar-neutrinos-astronaut-ice-cream-and-flavor-physics\/\">crash course in neutrino flavor<\/a>.<\/p>\n<p>When neutrinos interact with ambient nuclei through a\u00a0<em>W<\/em> boson (<strong>charged current<\/strong> interactions), the following types of events might be seen:<\/p>\n<figure id=\"attachment_2987\" aria-describedby=\"caption-attachment-2987\" style=\"width: 599px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-03-31-at-4.31.03-PM.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2987\" src=\"http:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-03-31-at-4.31.03-PM.png\" alt=\"Types of Ice Cube Events\" width=\"599\" height=\"324\" srcset=\"https:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-03-31-at-4.31.03-PM.png 599w, https:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-03-31-at-4.31.03-PM-300x162.png 300w\" sizes=\"auto, (max-width: 599px) 100vw, 599px\" \/><\/a><figcaption id=\"caption-attachment-2987\" class=\"wp-caption-text\">Typical\u00a0charged current events in IceCube. Displays from the <a href=\"http:\/\/arxiv.org\/abs\/1405.5303\">IceCube collaboration<\/a>.<\/figcaption><\/figure>\n<p>I refer you to <a href=\"http:\/\/www.quantumdiaries.org\/2010\/02\/14\/lets-draw-feynman-diagams\/\">this series of posts<\/a> for a gentle introduction to the Feynman diagrams above.\u00a0The key is that the high energy neutrino interacts with an\u00a0nucleus, breaking it apart (the remnants are called\u00a0<em>X<\/em> above) and ejecting a high energy charged lepton\u00a0which can be used to identify the flavor of the neutrino.<\/p>\n<ul>\n<li>Muons\u00a0travel a long distance and leave behind\u00a0a trail\u00a0of <a href=\"http:\/\/en.wikipedia.org\/wiki\/Cherenkov_radiation\">Cerenkov radiation<\/a>\u00a0called a\u00a0<strong>track<\/strong>.<\/li>\n<li>Electrons\u00a0don&#8217;t travel as far and\u00a0deposit all of their energy\u00a0into a\u00a0<strong>shower<\/strong>. These are also sometimes called\u00a0<strong>cascades <\/strong>because of the chain of particles produced in the &#8216;bang&#8217;.<\/li>\n<li>Taus typically leave a more dramatic signal, a<strong> double bang<\/strong>, when the tau is formed and then subsequently decays into more\u00a0hadrons (<em>X&#8217;<\/em> above).<\/li>\n<\/ul>\n<p>In fact,\u00a0the tau events\u00a0can be further classified depending on how this &#8216;double bang&#8217;\u00a0is\u00a0resolved&#8212;and\u00a0it seems like someone was playing a popular candy-themed mobile game when naming these:<\/p>\n<figure id=\"attachment_2990\" aria-describedby=\"caption-attachment-2990\" style=\"width: 534px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/CowenCandy.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-2990\" src=\"http:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/CowenCandy.png\" alt=\"Types of tau events in IceCube from Cowan.\" width=\"534\" height=\"398\" srcset=\"https:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/CowenCandy.png 534w, https:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/CowenCandy-300x224.png 300w\" sizes=\"auto, (max-width: 534px) 100vw, 534px\" \/><\/a><figcaption id=\"caption-attachment-2990\" class=\"wp-caption-text\">Types of candy-themed tau events in IceCube from D.\u00a0<a href=\"http:\/\/iopscience.iop.org\/1742-6596\/60\/1\/048\/pdf\/1742-6596_60_1_048.pdf\">Cowan<\/a>\u00a0at the TeVPA 2 conference.<\/figcaption><\/figure>\n<p>In this figure from the <a href=\"http:\/\/iopscience.iop.org\/1742-6596\/60\/1\/048\/\">TeVPA 2 conference proceedings<\/a>, we find some silly classifications\u00a0of what tau events look like according to their energy:<\/p>\n<ul>\n<li><strong>Lollipop<\/strong>: The tau is produced outside the detector so that the first &#8216;bang&#8217; isn&#8217;t seen. Instead, there&#8217;s a visible track that leads to the second (observable) bang.\u00a0The track is the stick and the bang is the lollipop head.<\/li>\n<li><strong>Inverted lollipop<\/strong>: Similar\u00a0to the lollipop, except now the first &#8216;bang&#8217; is seen in the detector but the second &#8216;bang&#8217; occurs outside the detector and is not observed.<\/li>\n<li><strong>Sugardaddy<\/strong>: The tau is produced outside the detector but decays into a muon inside the detector. This looks almost like a muon track except that the tau produces less Cerenkov light so that one can identify the point where the tau decays into a muon.<\/li>\n<li><strong>Double pulse<\/strong>: While this isn&#8217;t candy-themed, it&#8217;s still very interesting. This is a double bang where the two bangs can&#8217;t be distinguished\u00a0spatially. However, since one bang occurs slightly after the other, one can distinguish them\u00a0in the time: it&#8217;s a &#8220;double bang&#8221; in time rather than space.<\/li>\n<li><strong>Tautsie pop<\/strong>: This is a low energy version of the sugardaddy where the shower-to-track energy is used to\u00a0discriminate against background.<\/li>\n<\/ul>\n<p>While the names may be silly,\u00a0counting these types of events in IceCube is one of the exciting\u00a0frontiers of flavor physics. And while we might be forgiven for thinking that neutrino physics is all about measuring very `small&#8217; things&#8212;let me share the following graphic from Francis Halzen&#8217;s <a href=\"https:\/\/indico.cern.ch\/event\/381134\/timetable\/#all\">recent talk at the AMS Days workshop at CERN<\/a>, overlaying one of the\u00a0shower events over\u00a0Madison, Wisconsin to give a sense of scale:<\/p>\n<figure id=\"attachment_2989\" aria-describedby=\"caption-attachment-2989\" style=\"width: 591px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-04-16-at-10.10.57-AM.png\"><img loading=\"lazy\" decoding=\"async\" class=\"wp-image-2989 size-full\" src=\"http:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-04-16-at-10.10.57-AM.png\" alt=\"From F. Halzen on behalf of the IceCube collaboration.\" width=\"591\" height=\"483\" srcset=\"https:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-04-16-at-10.10.57-AM.png 591w, https:\/\/www.particlebites.com\/wp-content\/uploads\/2015\/04\/Screen-Shot-2015-04-16-at-10.10.57-AM-300x245.png 300w\" sizes=\"auto, (max-width: 591px) 100vw, 591px\" \/><\/a><figcaption id=\"caption-attachment-2989\" class=\"wp-caption-text\">From F. Halzen on behalf of the IceCube collaboration; from <a href=\"https:\/\/indico.cern.ch\/event\/381134\/timetable\/#all\">AMS Days at CERN 2015<\/a>.<\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"<p>Tau events in the IceCube ultra high energy neutrino detector can be classified depending on how the &#8216;double bang&#8217; is resolved&#8212;and it seems like someone was playing a popular candy-themed mobile game when naming these.<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[8],"tags":[32,4],"class_list":["post-2986","post","type-post","status-publish","format-standard","hentry","category-particlebites-summary","tag-icecube","tag-neutrinos"],"_links":{"self":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts\/2986","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2986"}],"version-history":[{"count":5,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts\/2986\/revisions"}],"predecessor-version":[{"id":4662,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=\/wp\/v2\/posts\/2986\/revisions\/4662"}],"wp:attachment":[{"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2986"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2986"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.particlebites.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2986"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}