Abstract
A search for single production of vector-like top quark partners (T) decaying into a Higgs boson and a top quark is performed using data from pp collisions at a centre-of-mass energy of 13 TeV collected by the CMS experiment at the CERN LHC, corresponding to an integrated luminosity of 2.3 fb−1. The top quark decay includes an electron or a muon while the Higgs boson decays into a pair of b quarks. No significant excess over standard model backgrounds is observed. Exclusion limits on the product of the production cross section and the branching fraction are derived in the T quark mass range 700 to 1800 GeV. For a mass of 1000 GeV, values of the product of the production cross section and the branching fraction greater than 0.8 and 0.7 pb are excluded at 95% confidence level, assuming left- and right-handed coupling of the T quark to standard model particles, respectively. This is the first analysis setting exclusion limits on the cross section of singly produced vector-like T quarks at a centre-of-mass energy of 13 TeV.
Highlights
Over the past decades several theoretical models have been formulated trying to give new insights into electroweak symmetry breaking and the mechanisms that stabilise the mass of the Higgs boson
Exclusion limits are set on the product of the production cross section and the branching fraction for single production of a vector-like T quark decaying to a top quark and a Higgs boson
The 95% confidence level (CL) exclusion limits are derived with a Bayesian statistical method [57,58], where background and signal templates in the MT distribution are used to make a combined fit to the data in the electron and muon channels
Summary
Over the past decades several theoretical models have been formulated trying to give new insights into electroweak symmetry breaking and the mechanisms that stabilise the mass of the Higgs boson. Many of these models predict the existence of heavy vectorlike quarks. While most of the past searches considered pair production of the T quarks via the strong interaction, the single production mode where the T quark is produced via the weak interaction has recently been investigated by the ATLAS Collaboration [16,19,20] at 8 TeV, and is targeted in this letter. For a T quark mass in the TeV range, the Higgs boson and the top quark obtain large Lorentz boosts leading to merged jets and nonisolated leptons in the final state. The shape of the total background is estimated from a signal-depleted region in the recorded data
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