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We study the charge asymmetry between the $t$ and $\bar t$ quark at the LHC,when they are produced in association with a $W$ boson. Though sizably reducingthe cross section with respect to the inclusive production, requiring a $W$boson in the final state has two important implications. First, at leadingorder in QCD, $t \bar t W^{\pm}$ production can only occur via $q \bar q$annihilation. As a result, the asymmetry between the $t$ and $\bar t$ generatedat NLO in QCD is significantly larger than that of inclusive $t \bar t$production, which is dominated by gluon fusion. Second, the top quarks tend toinherit the polarization of the initial-state quarks as induced by the$W$-boson emission. Hence, the decay products of the top quarks display asizable asymmetry already at the leading order in QCD. We study the relevantdistributions and their uncertainties in the standard model, compare them tothose obtained in a simple axigluon model and discuss prospects formeasurements at the LHC and beyond.

Top-quark charge asymmetry and polarization in $t\bar{t}W^\pm$ production at the LHC