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

Understand

The standard model (SM) production of four top quarks ($\mathrm{t\bar{t}t\bar{t}}$) in proton-proton collision 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 fb$^{-1}$ at a center-of-mass energy of 13 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 $\mathrm{t\bar{t}t\bar{t}}$ signal are respectively 2.6 and 2.7 standard deviations, and the $\mathrm{t\bar{t}t\bar{t}}$ cross section is measured to be 12.6 $^{+5.8}_{-5.2}$ fb.