Search for single production of a heavy vector-like T quark decaying to a top quark and a Higgs boson with the CMS Experiment

The presented work is a search for single production of vector-like T quarks.Vector-like quarks are common among non-SUSY theories that strive to solve the hierarchy problem.The search is undertaken with 2.3$\,$fb of proton-proton collisions at a centre of mass energy of $\sqrt s=13\,$TeV, recorded with the CMS experiment at the CERN LHC in 2015.The T quark decay channel into a top quark and a Higgs boson is considered.A mass-range from 700$\,$GeV up to 1800$\,$GeV is scanned, where the top quark and Higgs boson acquire a significant Lorentz boost.An electron or muon in the final state is required, as well as a collimated pair of b quarks from the decay of the boosted Higgs boson.The search is performed as a shape analysis with a signal plus background model, fitted to the data.The shape of the background is extracted from a signal-depleted control region in the data.The background shape describes the observed data well and no excess of events is seen.Exclusion limits are derived for the single T quark production cross section times the branching fraction of the T quark decay into a Higgs boson and a top quark.A Bayesian statistical method is applied.At 95\% confidence level, values of 0.49$\,$pb and 0.18$\,$pb (0.42$\,$pb and 0.14$\,$pb) for T quark masses of 1200$\,$GeV and 1700$\,$GeV, respectively, are excluded for T quark production in association with b (top) quarks.These are the first results on singly produced vector-like quarks published by the CMS Collaboration and the first results from the LHC at $\sqrt s=13\,$TeV.