Search for Standard Model Production of Four Top Quarks in Proton-Proton Collisions at 13 TeV in the Opposite-Sign Dilepton Channel Using CMS Data From 2017 and 2018
Abstract
A search for a rare Standard Model Process, four top quark production in the di-lepton plusjets final state (e e, μ μ, and e μ), is presented. The analysis utilizes data equivalent to 101.5 fb−1 of luminosity at √s = 13 TeV recorded by the CMS experiment during 2017 and 2018. Following a baseline selection to choose events with a pair of opposite sign charged leptons, four or more hadronic jets, of which at least 2 jets are b-tagged, the data are classified in bins of jet multiplicity (4, 5, 6, 7, and 8 or more jets), and b-tag multiplicity (2, 3, and 4 or more b-tagged jets). Events with at least 7 jets and 3 b-tagged jets are the most sensitive to the tttt signal. The HT distributions for the 15 categories per year and decay channel are fitted to simulation using Maximum Likelihood Estimation to obtain an upper limit on the cross section σtt tt . An a-priori expected limit of 3.3+4.6−1.7 × σSMtt tt (39+56−20fb) is obtained at the 95% CL, with an a-priori expected signal significance of 0.65σ. The a-posteriori asymptotic limits are 3.0+4.4−1.6 × σSMtt tt (36+53−19fb). The asymptotic observed limits are 6.0 × σSMtt tt (72fb) with a significance of 1.6σ.