Search for decays of stopped long-lived particles produced in proton-proton collisions at √s=8 TeV

Khachatryan, V. and Sirunyan, A. M. and Tumasyan, A. and Adam, W. and Bergauer, T. and Filipovic, Nicolas and Bencze, György and Hajdu, Csaba and Hidas, Pál and Horváth, Dezső and Siklér, Ferenc and Veszprémi, Viktor and Vesztergombi, György and Zsigmond, Anna Júlia and Karancsi, János and Molnár, József and Makovec, Alajos and Trócsányi, Zoltán and Ujvári, Balázs and Veres, Gábor (2015) Search for decays of stopped long-lived particles produced in proton-proton collisions at √s=8 TeV. EUROPEAN PHYSICAL JOURNAL C, 75 (4). ISSN 1434-6044

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Abstract

A search has been performed for long-lived particles that could have come to rest within the CMS detector, using the time intervals between LHC beam crossings. The existence of such particles could be deduced from observation of their decays via energy deposits in the CMS calorimeter appearing at times that are well separated from any proton-proton collisions. Using a data set corresponding to an integrated luminosity of 18.6 fb−1 of 8 TeV proton-proton collisions, and a search interval corre- sponding to 281 hours of trigger livetime, 10 events are observed, with a background prediction of 13.2+3.6 −2.5 events. Limits are presented at 95% confidence level on gluino and top squark production, for over 13 orders of magnitude in the mean proper life- time of the stopped particle. Assuming a cloud model of R-hadron interactions, a gluino with mass .1000 GeV and a top squark with mass .525 GeV are excluded, for lifetimes between 1 μs and 1000 s. These results are the most stringent constraints on stopped particles to date.

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