Evidence for four-top quark production in proton-proton collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.svg"><mml:msqrt><mml:mrow><mml:mi>s</mml:mi></mml:mrow></mml:msqrt><mml:mo linebreak="goodbreak" linebreakstyle="after">=</mml:mo><mml:mn>13</mml:mn><mml:mspace width="0.2em" /><mml:mtext>TeV</mml:mtext></mml:math>

The production of four top quarks ($\mathrm{t\bar{t}t\bar{t}}$) is studied with LHC proton-proton collision data samples collected by the CMS experiment at a center-of-mass energy 13 TeV, and corresponding to integrated luminosities up 138 fb$^{-1}$. Events that have no leptons (all-hadronic), one lepton, or two opposite-sign (where lepton refers only prompt electrons muons) are considered. This first $\mathrm{t\bar{t}t\bar{t}}$ measurement includes all-hadronic final state. observed significance signal in these states 3.9 standard deviations (1.5 expected) provides evidence for production, measured cross section 36 $^{+12}_{-11}$ fb. Combined earlier results other states, 4.0 (3.2 expected). combination returns an 17 $\pm$ 4 (stat) 3 (syst) fb, which consistent model prediction.