Measurement of the W boson helicity fractions in the decays of top quark pairs to lepton + jets final states produced in pp collisions at √s=8TeV

Abstract

The W boson helicity fractions from top quark decays in events are measured using data from proton–proton collisions at a centre-of-mass energy of . The data were collected in 2012 with the CMS detector at the LHC, corresponding to an integrated luminosity of . Events are reconstructed with either one muon or one electron, along with four jets in the final state, with two of the jets being identified as originating from b quarks. The measured helicity fractions from both channels are combined, yielding , , and for the longitudinal, left-, and right-handed components of the helicity, respectively. These measurements of the W boson helicity fractions are the most accurate to date and they agree with the predictions from the standard model.