Search for the single production of vector-like quarks decaying into a W boson and a b quark using single-lepton final states in proton-proton collisions at $\sqrt{s}$ = 13 TeV

A search is performed for the single production of a heavy vector-like quark (VLQ), decaying into a W boson and a b quark. The analysis uses proton-proton collision data collected by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV and corresponding to an integrated luminosity of 138 fb$^{-1}$. The search targets events with leptonic W boson decays. The event signature consists of one electron or muon, large transverse momentum imbalance, at least one jet consistent with coming from the fragmentation of a b quark and having large transverse momentum, and at least one jet in the forward region of the detector. No significant excess over the standard model prediction is observed. Upper limits are set at the 95% confidence level on the production cross section of a VLQ and its coupling $\kappa_\mathrm{W}$ to the standard model sector. For a VLQ decaying exclusively into Wb, the upper limit on $\kappa_\mathrm{W}$ depends on the VLQ mass and reaches values as low as 0.086 for masses around 1.4 TeV. For $\kappa_\mathrm{W}$ = 0.2 the lower limit on the VLQ mass is 2.4 TeV. These are the most stringent limits to date on the single production of VLQs decaying into Wb.