Search for production of four top quarks in final states with same-sign or multiple leptons in proton-proton collisions at s = 13 TeV

Abstract

The standard model (SM) production of four top quarks ( $\text{t}\overline{\text{t}}\text{t}\overline{\text{t}}$ ) in proton-proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking of the LHC, corresponds to an integrated luminosity of 137 ${\text{fb}}^{-1}$ at a center-of-mass energy of 13 $\text{TeV}$ . The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the $\text{t}\overline{\text{t}}\text{t}\overline{\text{t}}$ signal are respectively 2.6 and 2.7 standard deviations, and the $\text{t}\overline{\text{t}}\text{t}\overline{\text{t}}$ cross section is measured to be $12.6_{-5.2}^{+5.8}\text{fb}$ . The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, $y_{\text{t}}$ , yielding a limit of $|y_{\text{t}}/y_{\text{t}}^{\mathrm{SM}}|<1.7$ at $95\%$ confidence level, where $y_{\text{t}}^{\mathrm{SM}}$ is the SM value of $y_{\text{t}}$ . They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, $\hat{H}<0.12$ . Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350-470 $\text{GeV}$ and 350-550 $\text{GeV}$ for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.