Impact of leptonp_Tthreshold on charge asymmetry predictions for inclusiveWboson production inppcollisions at 13 TeV

Abstract：

This paper presents the impact of the lepton transverse momentum $p^{l}_{T}$ threshold on the $W$ boson charge asymmetry predictions in perturbative QCD for the inclusive $W^{\pm}+X \rightarrow l^{\pm} \nu +X$ production in proton-proton ( $pp$ ) collisions. The predictions are obtained at various low- $p^{l}_{T}$ thresholds $p^{l}_{T} >$ 20, 25, 30, and 40 GeV in a fiducial region encompassing both the central and forward detector acceptances in terms of the lepton pseudorapidity $0 \leq \eta_{l} \leq 4.5$ . The predicted distributions for the lepton charge asymmetry, which is defined by $\eta_{l}$ ( $A_{\eta_{l}}$ ), at the next-to-next-to-leading order (NNLO) accuracy are compared with the CMS and LHCb data at 8 TeV center-of-mass collision energy. The 8 TeV predictions reproduce the data fairly well within the quoted uncertainties. The predictions from the CT14 parton distribution function (PDF) model are in a slightly better agreement with the data over the other PDF sets that are tested. The 13 TeV predictions using various $p^{l}_{T}$ thresholds are reported for $A_{\eta_{l}}$ and the charge asymmetries that are defined in terms of the differential cross sections in bins of the $W$ boson rapidity $y_{W}$ ( $A_{y_{W}}$ ) and transverse momentum $p^{W}_{T}$ ( $A_{p^{W}_{T}}$ ). The NNLO predictions for the $A_{\eta_{l}}$ , $A_{y_{W}}$ , and $A_{p^{W}_{T}}$ distributions are assessed to be in close correlation with the $p^{l}_{T}$ value. The $A_{\eta_{l}}$ and $A_{y_{W}}$ distributions are particularly shown to be more correlated at a higher $p^{l}_{T}$ threshold. The $A_{p^{W}_{T}}$ distributions are also reported from the merged predictions with improved accuracy by the inclusion of the next-to-next-to-next-to-leading logarithm (N ³LL) corrections, i.e., at NNLO+N ³LL. The predicted distributions from various $p^{l}_{T}$ thresholds represent a finer probe in terms of the capability to provide more constraints on the ratio of $u$ and $d$ quark distribution functions in the parton momentum fraction range $10^{-4} < x < 1$ .