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 \(\phantom{\rule{0.166667em}{0ex}}{\text{fb}}^{-1}\) at a center-of-mass energy of 13 \(\phantom{\rule{0.166667em}{0ex}}\text{TeV}\). 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 \(12.{6}_{-5.2}^{+5.8}\phantom{\rule{0.166667em}{0ex}}\text{fb}\). 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 \(\phantom{\rule{0.166667em}{0ex}}\text{GeV}\) and 350–550 \(\phantom{\rule{0.166667em}{0ex}}\text{GeV}\) for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.