Measurement of the W boson helicity in events with a single reconstructed top quark in pp collisions at s^1/2 = 8 TeV
Journal of High Energy Physics, Volume 2015, article id. #53
A measurement of the W boson helicity is presented, where the W boson originates from the decay of a top quark produced in pp collisions. The event selection, optimized for reconstructing a single top quark in the final state, requires exactly one isolated lepton (muon or electron) and exactly two jets, one of which is likely to originate from the hadronization of a bottom quark. The analysis is performed using data recorded at a center-of-mass energy of 8 TeV with the CMS detector at the CERN LHC in 2012. The data sample corresponds to an integrated luminosity of 19.7 fb-1. The measured helicity fractions are F_L = 0.298 ± 0.028 (stat) ± 0.032(syst), F_0 = 0.720 ± 0.039 (stat) ± 0.037(syst), and F_R = -0.018 ± 0.019 (stat) ± 0 .011(syst). These results are used to set limits on the real part of the tWb anomalous couplings, g_L and g_R.