Search for the associated Higgs boson production with top quarks in CMS

A precise determination of the Yukawa coupling to top quarks is crucial for the characterization of the recently discovered Higgs boson. A direct measurement of this coupling can be provided only by those processes where the Higgs boson is produced in association with top quarks. In the Standard Model (SM), the production of the Higgs boson together with a top-antitop pair ( tt‾H ) has the largest cross section, followed by the production with a single top quark ( tH ), with roughly one order of magnitude smaller rate. As of summer 2014, the CMS experiment at LHC has performed searches for either processes using the full Run-I data set in a variety of decay channels of the Higgs boson, namely H→WW⁎,ZZ⁎,τ+τ−,bb‾,γγ for the tt‾H production, and H→γγ for tH . Due to the small cross section, the sensitivity to the SM tH production is still far from being achieved, yet stringent constraints can be already set for non-SM couplings. Conversely, the combination of the various tt‾H searches has already attained sensitivity to measure a SM-like signal, providing a best-fit value of the signal strength modifier μˆ=2.76−0.92+1.05 , compatible with the SM expectation at the 2 σ level. An improved tt‾H search in the H→γγ channel using the full 7 and 8 TeV data set, as well as a new tt‾H , H→bb‾ analysis using a matrix element technique, are here presented for the first time.