A search for fermionic top quark partners $T$ of charge $2/3$ is presented. The search is carried out in proton-proton collisions corresponding to an integrated luminosity of $19.7{\mathrm{fb}}^{-1}$ collected at a center-of-mass energy of $\sqrt{s}=8\mathrm{TeV}$ with the CMS detector at the LHC. The $T$ quarks are assumed to be produced strongly in pairs and can decay into $tH$, $tZ$, and $bW$. The search is performed in five exclusive channels: a single-lepton channel, a multilepton channel, two all-hadronic channels optimized either for the $bW$ or the $tH$ decay, and one channel in which the Higgs boson decays into two photons. The results are found to be compatible with the standard model expectations in all the investigated final states. A statistical combination of these results is performed and lower limits on the $T$ quark mass are set. Depending on the branching fractions, lower mass limits between 720 and 920 GeV at 95% confidence level are found. These are among the strongest limits on vectorlike $T$ quarks obtained to date.

• Received 14 September 2015

DOI:https://doi.org/10.1103/PhysRevD.93.012003

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© 2016 CERN, for the CMS Collaboration