Search for production of four top quarks in final states with same-sign or multiple leptons in proton-proton...

The standard model (SM) production of four top quarks ( $$ ) in proton-proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016-2018 data taking of the LHC, corresponds to an integrated luminosity of 137 $$ at a center-of-mass energy of 13 $$ . The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the $$ signal are respectively 2.6 and 2.7 standard deviations, and the $$ cross section is measured to be $$ . The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, $$ , yielding a limit of $$ at $$ confidence level, where $$ is the SM value of $$ . They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, $$ . 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 $$ and 350-550 $$ for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.