A search is presented for single production of a vector-like T quark with charge 2/3 $e$, in the decay channel featuring a top quark and a Z boson, with the top quark decaying hadronically and the Z boson decaying to neutrinos. The search uses data collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 137 fb$^{-1}$ recorded at the CERN LHC in 2016-2018. The search is sensitive to a T quark mass between 0.6 and 1.8 TeV with decay widths ranging from negligibly small up to 30% of the T quark mass. Reconstruction strategies for the top quark are based on the degree of Lorentz boosting of its final state. At 95% confidence level, the upper limit on the product of the cross section and branching fraction for a T quark of small decay width varies between 15 and 602 fb, depending on its mass. For a T quark with decay widths between 10 and 30% of its mass, this upper limit ranges between 16 and 836 fb. For most of the studied range, the results provide the best limits to date. This is the first search for single T quark production based on the full Run 2 data set of the LHC.
Product of efficiency and acceptance of the event selection for T signal events as a function of the particle mass $m_\mathrm{T}$ and width $\Gamma$ for the different hypotheses considered.
Product of efficiency and acceptance of the event selection for T signal events as a function of the particle mass $m_\mathrm{T}$ and width $\Gamma$ for the different hypotheses considered.
Product of efficiency and acceptance of the event selection for T signal events as a function of the particle mass $m_\mathrm{T}$ and width $\Gamma$ for the different hypotheses considered.
A search for single production of a vector-like T quark with charge $2/3\,e$, in the decay channel with a top quark and a neutral scalar boson $\phi$ is presented. The $\phi$ boson can be a standard model Higgs boson or a new particle beyond the standard model. The top quark is identified in its leptonic decay, and the neutral boson decays into a bottom quark-antiquark pair. Final states with boosted topologies are considered and machine learning techniques are exploited for optimal classification. The analysis uses data collected by the CMS experiment in proton-proton collisions at a center-of-mass energy of $13~\mathrm{TeV}$, corresponding to an integrated luminosity of $138~\mathrm{fb}^{-1}$ recorded at the CERN LHC in 2016$-$2018. Limits at $95\%$ confidence levels are set on the product of the cross section and branching fraction for a T quark of small decay width. They are in the range between 15 and $0.15~\mathrm{fb}$, depending on T quark and $\phi$ boson masses. In the case of the decay channel with a top quark and a standard model Higgs boson, for most of the studied range the analysis provides limits which are better or comparable with previous searches performed in CMS.
Distribution of the mass of the AK8 jet selected as the $\phi$ boson candidate for data and simulated background events in the (TopT, XbbL) validation region for the muon channel. The distribution is shown before the final fit for signal extraction.
Distribution of the mass of the AK8 jet selected as the $\phi$ boson candidate for data and simulated background events in the (TopT, XbbL) validation region for the electron channel. The distribution is shown before the final fit for signal extraction.
Distribution of the mass of the AK8 jet selected as the $\phi$ boson candidate for data and simulated background events in the (TopL, XbbL) validation region for the muon channel. The distribution is shown before the final fit for signal extraction.
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