{"id":5218,"date":"2015-07-14T08:23:36","date_gmt":"2015-07-14T08:23:36","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=5218"},"modified":"2015-07-14T09:10:30","modified_gmt":"2015-07-14T09:10:30","slug":"cerns-lhcb-experiment-reports-observation-of-exotic-pentaquark-particles","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/cerns-lhcb-experiment-reports-observation-of-exotic-pentaquark-particles\/","title":{"rendered":"CERN\u2019s LHCb experiment reports observation of exotic pentaquark particles"},"content":{"rendered":"
\"Illustration<\/a>
Illustration of the possible layout of the quarks in a pentaquark particle such as those discovered at LHCb. The five quarks might be tightly bonded (left). They might also be assembled into a meson (one quark and one antiquark) and a baryon (three quarks), weakly bonded together.
Images: \u00a9 CERN \/ LHCb Collaboration<\/figcaption><\/figure>\n

Geneva–\u00a0Today, the LHCb experiment at CERN\u2019s Large Hadron Collider has reported the discovery of a class of particles known as pentaquarks. The collaboration has submitted a paper reporting these findings to the journal\u00a0Physical Review Letters<\/em>.<\/span><\/p>\n

\u201cThe pentaquark is not just any new particle,\u201d\u00a0said LHCb spokesperson Guy Wilkinson.\u00a0\u201cIt\u00a0represents a way to aggregate quarks, namely the fundamental constituents of ordinary protons and neutrons,\u00a0in a pattern that has never been observed before in over fifty\u00a0years of experimental searches. Studying its properties may allow us to understand better how ordinary matter, the protons and neutrons from which we\u2019re all made, is constituted.\u201d<\/span><\/p>\n

\"unnamed<\/a>Our understanding of the structure of matter was revolutionized in 1964 when American physicist, Murray Gell-Mann, proposed that a category of particles known as baryons, which includes protons and neutrons, are comprised of three fractionally charged objects called quarks, and that another category, mesons, are formed of quark-antiquark pairs. Gell-Mann was awarded the Nobel Prize in physics for this work in 1969. This quark model also allows the existence of other quark composite states, such as pentaquarks composed of four quarks and an antiquark. Until now, however, no conclusive evidence for pentaquarks had been seen.<\/span><\/p>\n

LHCb researchers looked for pentaquark states by examining the decay of a baryon known as \u039bb<\/sub>\u00a0(Lambda b) into three other particles, a J\/\u0471 (J-psi), a proton and a charged kaon. Studying the spectrum of masses of the J\/\u0471 and the proton revealed that intermediate states were sometimes involved in their production. These have been named Pc<\/sub>(4450)+<\/sup>\u00a0and Pc<\/sub>(4380)+<\/sup>, the former being clearly visible as a peak in the data, with the latter being required to describe the data fully.<\/span><\/p>\n

\u201cBenefitting from the large data set provided by the LHC, and the excellent precision of our detector, we have examined all possibilities for these signals, and conclude that they can only be explained by pentaquark states\u201d, says LHCb physicist Tomasz Skwarnicki of Syracuse University.<\/span><\/p>\n

\u201cMore precisely the states must be formed of two up quarks, one down quark, one charm quark and one anti-charm quark.\u201d<\/span><\/p>\n

\"unnamed<\/a>Earlier experiments that have searched for pentaquarks have proved inconclusive. Where the LHCb experiment differs is that it has been able to look for pentaquarks from many perspectives, with all pointing to the same conclusion. It\u2019s as if the previous searches were looking for silhouettes in the dark, whereas LHCb conducted the search with the lights on, and from all angles. The next step in the analysis will be to study how the quarks are bound together within the pentaquarks.<\/span><\/p>\n

\u201cThe quarks could be tightly bound,\u201d\u00a0said LHCb physicist Liming Zhang of Tsinghua University, \u201cor they could be loosely bound in a sort of meson-baryon molecule, in which the meson and baryon feel a residual strong force similar to the one binding protons and neutrons to form nuclei.\u201d<\/span><\/p>\n

More studies will be needed to distinguish between these possibilities, and to see what else pentaquarks can teach us. The new data that LHCb will collect in LHC run 2 will allow progress to be made on these questions.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

Geneva–\u00a0Today, the LHCb experiment at CERN\u2019s Large Hadron Collider has reported the discovery of a class of particles known as pentaquarks. The collaboration has submitted a paper reporting these findings to the journal\u00a0Physical Review Letters. \u201cThe pentaquark is not just any new particle,\u201d\u00a0said LHCb spokesperson Guy Wilkinson.\u00a0\u201cIt\u00a0represents a way to aggregate quarks, namely the fundamental […]<\/p>\n","protected":false},"author":6,"featured_media":5219,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14,17],"tags":[],"class_list":["post-5218","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-innovation","category-research"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",1607,906,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic-300x169.jpg",300,169,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",750,423,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic-1024x577.jpg",750,423,true],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",1536,866,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",1607,906,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",1200,677,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",870,490,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",600,338,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",600,338,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",760,428,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",550,310,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",95,54,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",640,361,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",96,54,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/07\/news-pic.jpg",150,85,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Innovation<\/a> Research<\/a>","tag_info":"Research","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5218","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=5218"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/5218\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/5219"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=5218"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=5218"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=5218"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}