CMS-PAS-TOP-18-003

CMS-PAS-TOP-18-003
Search for standard model production of four top quarks in final states with same-sign and multiple leptons in proton-proton collisions at $\sqrt{s}= $ 13 TeV
CMS Collaboration
March 2019

Abstract: The standard model (SM) production of four top quarks ($\mathrm{t\overline{t}t\overline{t}}$) is studied by the CMS Collaboration using proton-proton collision events collected in Run 2 of the CERN LHC, with a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 137 fb$^{-1}$. The events are required to contain a pair of same-sign leptons ($e, \mu$) or at least three leptons, and several jets. Two approaches are used to enhance signal sensitivity: first a simple classification based on the number of jets and b-tagged jets, and second a boosted decision tree (BDT) taking advantage of kinematic variables related to leptons and jets. Control regions are used to constrain the dominant SM backgrounds. The two approaches find consistent results compatible with next-to-leading-order SM predictions. The observed (expected) significance of the BDT analysis is 2.6 (2.7) standard deviations, and the $\mathrm{t\overline{t}t\overline{t}}$ cross section is measured to be 12.6$^{+5.8}_{-5.2}$ fb. These results are used to constrain the Yukawa coupling of the top quark, $y_{\rm{t}}$, yielding a 95% confidence level limit of $\|y_{\rm{t}}/y_{\rm{t}}^{\rm{SM}}\| < $ 1.7, where $y_{\rm{t}}^{\rm{SM}}$ is the SM value of $y_{\rm{t}}$. Limits are also set on the production of a heavy scalar or pseudoscalar in a type II 2HDM scenario, with exclusions in the mass ranges of 350-470 GeV and 350-550 GeV for heavy scalar and pseudoscalar bosons, respectively, for the 2HDM scenarios considered.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ; These preliminary results are superseded in this paper, EPJC 80 (2020) 75. The superseded preliminary plots can be found here.

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