The observation of Higgs boson production in association with a top quark-antiquark pair is reported, based on a combined analysis of proton-proton collision data at center-of-mass energies of √s=7, 8, and 13 TeV, corresponding to integrated luminosities of up to 5.1, 19.7, and 35.9 fb−1, respectively. The data were collected with the CMS detector at the CERN LHC. The results of statistically independent searches for Higgs bosons produced in conjunction with a top quark-antiquark pair and decaying to pairs of W bosons, Z bosons, photons, τ leptons, or bottom quark jets are combined to maximize sensitivity. An excess of events is observed, with a significance of 5.2 standard deviations, over the expectation from the background-only hypothesis. The corresponding expected significance from the standard model for a Higgs boson mass of 125.09 GeV is 4.2 standard deviations. The combined best fit signal strength normalized to the standard model prediction is 1.26+0.31−0.26.
Hungarian groups participated in the project: Wigner Research Centre for Physics, MTA-ELTE Lendület CMS Particle and Nuclear Physics Group, Roland Eotvos University (ELTE), Institute for Nuclear Research, Hungarian Academy of Sciences (Atomki) and University of Debrecen.
Observation of t¯tH Production, A. M. Sirunyan et al. (CMS Collaboration), Phys. Rev. Lett. 120, 231801 – Published 4 June 2018