Top-quark charge asymmetry and polarization in tt-W± production at the LHC

We study the charge asymmetry between the t and t- quarks at the LHC, when they are produced in association with a W boson. Though sizably reducing the cross section with respect to the inclusive production, requiring a W boson in the final state has two important implications. First, at leading order in QCD, tt-W± production can only occur via qq- annihilation. As a result, the asymmetry between the t and t- generated at NLO in QCD is significantly larger than that of inclusive tt- production, which is dominated by gluon fusion. Second, the top quarks tend to inherit the polarization of the initial-state quarks as induced by the W-boson emission. Hence, the decay products of the top quarks display a sizable asymmetry already at the leading order in QCD. We study the relevant distributions and their uncertainties in the standard model, compare them to those obtained in a simple axigluon model and discuss prospects for measurements at the LHC and beyond.