Electroweak gauge boson production at hadron colliders through O(alpha_s^2)

TL;DR

This work provides a fully differential NNLO QCD calculation for W and Z production in hadronic collisions, incorporating spin correlations, finite width effects, and γ−Z interference to support realistic lepton-cut observables. It develops an automated infrared-subtraction framework (sector decomposition) to combine double-virtual, real-virtual, and double-real contributions into infrared-safe results, and implements the method in a numerical program (FEWZ). The authors demonstrate precise, low-uncertainty predictions for Tevatron and LHC observables, including Z production under typical cuts and W cross sections in forward/central regions, with NNLO acceptances and ratios in agreement with data. The results reduce theoretical uncertainties to the sub-percent level for key observables, enabling stringent PDF constraints and high-precision electroweak measurements.

Abstract

We describe a calculation of the O(alpha_s^2) QCD corrections to the fully differential cross section for W and Z boson production in hadronic collisions. The result is fully realistic in that it includes spin correlations, finite width effects, gamma-Z interference and allows for the application of arbitrary cuts on the leptonic decay products of the W and Z. We have implemented this calculation into a numerical program. We demonstrate the use of this code by presenting phenomenological results for several future LHC analyses and recent Tevatron measurements, including the W cross section in the forward rapidity region and the central over forward cross section ratio.

Figures (2)

• Figure 1: The production cross section (left panel) and the acceptance (right panel) as functions of the lepton pseudorapidity cut for neutral current $l^+l^-$ production at the LHC. The two charged leptons are required to have $p_T > 25~{\rm GeV}$, and their invariant mass is constrained to $66 < M_{l^+l^-} < 116~{\rm GeV}$. The dotted green lines refer to the LO result for $\mu=M_Z/2$ and $\mu=2M_Z$, the solid red lines indicate the NLO result, and the dashed blue lines denote the NNLO result. We note that the $\mu=M_Z/2$ and $\mu=2M_Z$ NNLO lines almost completely overlap and are nearly indistinguishable in both panels, and that both NNLO lines are completely contained within the NLO results.
• Figure 2: The production cross section (left panel) and the acceptance (right panel) as functions of the lepton transverse momentum cut for neutral current $l^+l^-$ production at the LHC. The two charged leptons are required to have $|\eta|<2.5$, and their invariant mass is constrained to $66 < M_{l^+l^-} < 116~{\rm GeV}$. The dotted green lines refer to the LO result for $\mu=M_Z/2$ and $\mu=2M_Z$, the solid red lines indicate the NLO result, and the dashed blue lines denote the NNLO result.