CMS Collaboration2024-05-082024-05-082023CMS Collaboration. (2023). Evidence for four-top quark production in proton-proton collisions at s=13TeV<math><msqrt is="true"><mrow is="true"><mi is="true">s</mi></mrow></msqrt><mo linebreak="goodbreak" linebreakstyle="after" is="true">=</mo><mn is="true">13</mn><mspace width="0.2em" is="true"></mspace><mtext is="true">TeV</mtext></math>. Physics Letters B, 844, 138076. https://doi.org/10.1016/j.physletb.2023.138076https://hdl.handle.net/1911/115639The production of four top quarks (tt¯tt¯) is studied with LHC proton-proton collision data samples collected by the CMS experiment at a center-of-mass energy of 13 TeV, and corresponding to integrated luminosities of up to 138fb−1. Events that have no leptons (all-hadronic), one lepton, or two opposite-sign leptons (where lepton refers only to prompt electrons or prompt muons) are considered. This is the first tt¯tt¯ measurement that includes the all-hadronic final state. The observed significance of the tt¯tt¯ signal in these final states of 3.9 standard deviations (1.5 expected) provides evidence for tt¯tt¯ production, with a measured cross section of 36−11+12fb. Combined with earlier CMS results in other final states, the signal significance is 4.0 standard deviations (3.2 expected). The combination returns an observed cross section of 17±4(stat)±3(syst)fb, which is consistent with the standard model prediction.engExcept where otherwise noted, this work is licensed under a Creative Commons Attribution (CC BY) license. Permission to reuse, publish, or reproduce the work beyond the terms of the license or beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.Journal article1-s2-0-S0370269323004100-mainhttps://doi.org/10.1016/j.physletb.2023.138076