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

CMS Collaboration; Canelli, F; Chiochia, V; Kilminster, B; Robmann, P; et al (2016). Measurement of the W boson helicity fractions in the decays of top quark pairs to lepton + jets final states produced in pp collisions at $\sqrt{s}$ = 8 TeV. Physics Letters B, 762:512-534.

Abstract

The W boson helicity fractions from top quark decays in $t\overline{t}$ events are measured using data from proton–proton collisions at a centre-of-mass energy of 8TeV. The data were collected in 2012 with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8fb$^{−1}$. 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 $F_{0}=0.681±0.012(stat)±0.023(syst)$ , $F_{L}=0.323±0.008(stat)±0.014(syst)$, and $F_{R}=−0.004±0.005(stat)±0.014(syst)$ 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.

Abstract

The W boson helicity fractions from top quark decays in $t\overline{t}$ events are measured using data from proton–proton collisions at a centre-of-mass energy of 8TeV. The data were collected in 2012 with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8fb$^{−1}$. 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 $F_{0}=0.681±0.012(stat)±0.023(syst)$ , $F_{L}=0.323±0.008(stat)±0.014(syst)$, and $F_{R}=−0.004±0.005(stat)±0.014(syst)$ 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.

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