Search for the standard model Higgs boson produced in association with top quarks in multilepton final states

A search for the standard model Higgs boson produced in association with a top quark pair is presented, using 19.6~fb$^{-1}$ of 8 TeV $\mathrm{pp}$ collision data collected by the CMS experiment at the LHC. Final states with a Higgs boson that decays to either $\mathrm{ZZ}^{*}$,$\mathrm{WW}^{*}$, or $\tau\tau$ are required to have a top quark pair that decays to either lepton plus jets ($\mathrm{t\bar{t}} \rightarrow \ell\nu\mathrm{jjb\bar{b}}$) or dileptons ($\mathrm{t\bar{t}} \rightarrow \ell \nu \ell \nu \mathrm{b\bar{b}}$), where $\ell$ represents an electron or a muon. The following signatures are selected: two isolated same-sign leptons (electrons or muons) plus b-tagged jets, three isolated leptons plus b-tagged jets, or four isolated leptons plus b-tagged jets. The expected 95\% confidence level upper limit on the Higgs boson production cross section for a Higgs boson mass of 125.7 GeV/c$^2$ is $2.4$ times the standard model expectation, to be compared to an observed limit of $6.6$. The signal strength $\mu$, relative to the expectation for the standard model Higgs boson, is measured to be $\mu =3.7^{+1.6}_{-1.4}$.