NNLO QCD Predictions of Charge Asymmetry Distributions for Inclusive ${W}$-Boson Hadroproduction

Abstract

Higher-order QCD predictions of charge asymmetry distributions are presented for inclusive $W^{\pm}+X\to l^{\pm}\nu+X$ production in proton–proton ($pp$) collisions at 8, 13, and 14 TeV center-of-mass energies. The $W$ boson or the decay lepton charge asymmetries constitute a direct probe of the relative $u$ and $d$ quark distributions in the proton as functions of the initial-state parton momentum fractions. The predictions for the charge asymmetry distributions are acquired at next-to-next-to-leading order (NNLO) accuracy in the perturbative QCD domain, exploiting several parton distribution function (PDF) models. The predicted lepton charge asymmetry distributions are justified with the 8 TeV measurements by the LHC experiments in both central and forward acceptance regions of the lepton pseudorapidities $0\leq\eta\leq 2.4$ and $2.0\leq\eta\leq 4.25$, and are provided thoroughly for both the regions at 13 and 14 TeV $pp$ collisions energies. Additionally, the impact of various lepton transverse momentum $p^{l}_{T}$ thresholds on the lepton (or the $W$ boson) charge asymmetry predictions at NNLO accuracy are presented in the fiducial region encompassing both central and forward detector acceptances of the lepton pseudorapidity $0\leq\eta_{l}\leq 4.5$. The lepton and $W$ boson charge asymmetry distributions are assessed to be in close correlation with the $p^{l}_{T}$ threshold, where the distributions are particularly observed to be more correlated at a higher-$p^{l}_{T}$ threshold. The $W$ boson asymmetry distribution as a function of the $W$ boson transverse momentum $p^{W}_{T}$ is also presented with improved accuracy by matching the NNLO predictions to resummed logarithmic corrections. Overall, the predicted results represent a substantial contribution in the context of the high-precision phenomenological studies.