Search for flavor changing neutral currents in top quark decays using a two-leptons+track selection

Top Quark;Flavor changing neutral currents (FCNC);Top Quark Decays;A Toroidal LHC Apparatus (ATLAS);European Organization for Nuclear Research (CERN)

Cortes Gonzalez, Arely

关键词: Top Quark;    Flavor changing neutral currents (FCNC);    Top Quark Decays;    A Toroidal LHC Apparatus (ATLAS);    European Organization for Nuclear Research (CERN);   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/42249/Arely_Cortes%20Gonzalez.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

A search for flavor-changing neutral currents in top quark decays is described. Data collected at a center- of-mass energy of √s = 7 TeV during 2011 corresponding to an integrated luminosity of 2.1 fb^{-1} are used. A cut-based analysis is used on top quark pair production events, where one top quark is assumed to follow the dominant Standard Model decay t->Wb, and the other the flavor changing neutral current decay t->Zq. Only the decays of the Z-boson to charged leptons and leptonic W-boson decays are considered signal. The search uses an event selection with two identified leptons (electrons and/or muons) and one lepton selected via inner-detector track requirements only (track lepton). Backgrounds to the search are evaluated using almost entirely data-driven techniques. An orthogonal channel, with three identified leptons is also described, and used in the final result. No significant excess is observed in the signal region. An upper limit on the t->qZ branching ratio of BR(t->Zq) <0.73% is set at the 95% confidence level, compatible with the expected limit.