Search for anomalous Wtb couplings and flavour-changing neutral currents in t-channel single top quark production in pp collisions at root s=7 and 8 TeV

Abstract

Single top quark events produced in the t channel are used to set limits on anomalous Wtb couplings and to search for top quark flavour-changing neutral current (FCNC) interactions. The data taken with the CMS detector at the LHC in proton-proton collisions at and 8 TeV correspond to integrated luminosities of 5.0 and 19.7 fb(-1), respectively. The analysis is performed using events with one muon and two or three jets. A Bayesian neural network technique is used to discriminate between the signal and backgrounds, which are observed to be consistent with the standard model prediction. The 95% confidence level (CL) exclusion limits on anomalous right-handed vector, and left- and right-handed tensor Wtb couplings are measured to be vertical bar f (V) (R) vertical bar < 0.16,aEuro,vertical bar f (T) (L) vertical bar < 0.057, and - 0.049 < f (T) (R) < 0.048, respectively. For the FCNC couplings kappa (tug) and kappa (tcg), the 95% CL upper limits on coupling strengths are vertical bar kappa (tug)vertical bar/I > < 4.1 x 10(- 3) TeV-1 and vertical bar kappa (tcg)vertical bar/Lambda < 1.8 x 10(- 2) TeV-1, where I > is the scale for new physics, and correspond to upper limits on the branching fractions of 2.0 x 10(-5) and 4.1 x 10(-4) for the decays t -> ug and t -> cg, respectively.