Search for top quark decays via Higgs-boson-mediated flavor changing neutral currents in pp collisions at~$\sqrt{s}$~=~8~TeV

A search for top quark decays via Higgs-boson-mediated flavor changing neutral currents ${\rm pp \rightarrow t\bar{t} \rightarrow \rm Hc + Wb}$ in events containing a trilepton or same-sign dilepton is presented. The search is performed with a data sample with an integrated luminosity of 19.7 fb$^{-1}$ of pp collisions at $\sqrt{s} = 8 \rm TeV$ collected with the CMS detector at the CERN LHC. The observed number of events agrees with the SM prediction, and no evidence for top quark decays via Higgs-boson-mediated flavor changing neutral currents are found. The measured 95\% confidence level observed and expected upper limits on the $\rm t \to Hc$ branching fraction are 0.93\% and 0.89\% respectively. This corresponds to an observed upper limit on top-charm flavor violating Higgs Yukawa coupling of $\sqrt{\left|\lambda_{tc}^{H}\right|^{2} + \left|\lambda_{ct}^{H}\right|^{2}} < 0.18$.