Single-Spin Asymmetries in W Boson Production at Next-to-Leading Order

TL;DR

This paper provides an analytic next-to-leading order QCD calculation of single-spin asymmetries in W boson production, facilitating faster analysis of proton helicity distributions at RHIC.

Contribution

It introduces an analytic NLO calculation method for single-spin asymmetries in W production, improving computational efficiency for global nucleon structure studies.

Findings

Analytic NLO cross sections match Monte Carlo results.

The calculation enables rapid analysis of RHIC data.

Comparison with existing polarized parton distribution sets.

Abstract

We present an analytic next-to-leading order QCD calculation of the partonic cross sections for single-inclusive lepton production in hadronic collisions, when the lepton originates from the decay of an intermediate electroweak boson and is produced at high transverse momentum. In particular, we consider the case of incoming longitudinally polarized protons for which parity-violating single-spin asymmetries arise that are exploited in the $W$ boson program at RHIC to constrain the proton's helicity parton distributions. Our calculation enables a very fast and efficient numerical computation of the relevant spin asymmetries at RHIC, which is an important ingredient for the inclusion of RHIC data in a global analysis of nucleon helicity structure. We confirm the validity of our calculation by comparing with an existing code that treats the next-to-leading order cross sections entirely numerically by Monte-Carlo integration techniques. We also provide new comparisons of the present RHIC data with results for some of the sets of polarized parton distributions available in the literature.