Measurement of the forward-backward asymmetry in the distribution of leptons intt¯events in thelepton+jetschannel

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Abstract

We present measurements of the forward-backward asymmetry in the angular distribution of leptons from decays of top quarks and antiquarks produced in proton-antiproton collisions. We consider the final state containing a lepton and at least three jets. The entire sample of data collected by the D0 experiment during Run II of the Fermilab Tevatron Collider, corresponding to $9.7\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of integrated luminosity, is used. The asymmetry measured for reconstructed leptons is ${A}_{\mathrm{FB}}^{l}=(2.9\ifmmode\pm\else\textpm\fi{}2.1{(\text{stat}.)}_{\ensuremath{-}1.7}^{+1.5}(\text{syst}.))%$. When corrected for efficiency and resolution effects within the lepton rapidity coverage of $|{y}_{l}|<1.5$, the asymmetry is found to be ${A}_{\mathrm{FB}}^{l}=(4.2\ifmmode\pm\else\textpm\fi{}2.3{(\text{stat}.)}_{\ensuremath{-}2.0}^{+1.7}(\text{syst}.))%$. We examine the dependence of ${A}_{\mathrm{FB}}^{l}$ on the transverse momentum and rapidity of the lepton. Combination with the asymmetry measured in the final states containing two leptons yields ${A}_{\mathrm{FB}}^{l}=(4.2\ifmmode\pm\else\textpm\fi{}2.0(\text{stat}.)\ifmmode\pm\else\textpm\fi{}1.4(\text{syst}.))%$. The results are in agreement with predictions from the next-to-leading-order QCD generator mc@nlo, which predicts an asymmetry of ${A}_{\mathrm{FB}}^{l}=2.0%$ for $|{y}_{l}|<1.5$.

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