Search for the singly-produced vector-like partner of the top quark decaying into a W\texorpdfstring{$^{\pm}$} boson and a b quark

We present a search for the single production of a heavy vector-like quark, decaying into a W boson and a b quark. The search is performed using the data sample of pp collisions at a center of mass energy of $\sqrt{s} = 13$ TeV collected by the CMS experiment at the Large Hadron Collider in 2015. The dataset used in the analysis corresponds to 2.3~fb$^{-1}$ of integrated luminosity. The search is carried out using events containing one electron or muon, at least one b-tagged jet with large transverse momentum, at least one jet in the forward region of the detector, and missing transverse energy. No excess over the standard model predictions is observed. Upper bounds are placed on the production cross section of heavy top quark partners, T quark with a charge of 2/3e and Y quark with a charge of $-$4/3e. The results are also interpreted as limits on the mass of the vector-like quark and its coupling to the W boson and the b quark. T quarks with masses below 1.73 TeV are excluded at 95\% C.L. assuming a unit coupling and a BR(T$\rightarrow$Wb) = 0.5, while the expected limit is 1.42~TeV. Y quarks with coupling of 0.5 and BR(Y$\rightarrow$Wb) = 1 are excluded below 1.40 TeV, whereas the expected limit is 0.99~TeV. %are excluded below 1.5 %with masses below 1.75 TeV are excluded at 95\% C.L. assuming a unit coupling and a BR(T$\rightarrow$Wb) = 0.5, while the expected limit is 1.45~TeV.