W-boson production in polarized proton-proton collisions at RHIC through next-to-next-to-leading order in perturbative QCD

Radja Boughezal,Hai Tao Li,Frank Petriello

doi:10.1016/j.physletb.2021.136333

Radja Boughezal, Hai Tao Li + Show 1 more

Open Access

https://doi.org/10.1016/j.physletb.2021.136333

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Abstract

We perform a study of W-boson production in polarized proton-proton collisions through next-to-next-to-leading order (NNLO) in perturbative QCD. This calculation is required to extend the extraction of polarized parton distribution functions to NNLO accuracy. We present differential distributions at s=510 GeV, relevant for comparison to measurements from the Relativistic Heavy Ion Collider (RHIC). The NNLO QCD corrections significantly reduce the scale dependence of the cross section. We compare the longitudinal single-spin asymmetries as a function of lepton pseudorapidity to RHIC data. The asymmetries exhibit excellent stability under perturbative QCD corrections.

Highlights

Over the past several years new insight into aspects of polarized proton structure has been provided by the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory
In principle our polarized cross section should be combined with a nextto-next-to-leading order (NNLO) extraction of polarized parton distribution functions (PDFs), but as discussed in the introduction no such set currently exists
We have presented a calculation of the NNLO perturbative corrections to W ± production in polarized protonproton collisions

Summary

INTRODUCTION

An understanding of how the spin of the proton arises from its partonic constituents is an outstanding problem in fundamental physics. Jet and pion production in polarized proton-proton collisions at RHIC indicate that gluons contribute a non-negligible amount to the proton spin [3] Another recent result which motivates this paper is the first evidence of flavor asymmetry in the polarized sea. The relevant observables that lead to this result are the single-spin asymmetries in polarized pp → W ±, where the W -bosons decay via W + → e+νand W − → e−ν: AL = (σ+ − σ−)/(σ+ + σ−), where σ± denotes the cross section with a single proton beam with positive or negative helicity. In this paper we take a step toward this goal by calculating W -boson production in polarized proton-proton collisions to NNLO in perturbative QCD.

CALCULATIONAL FRAMEWORK

NUMERICAL RESULTS

CONCLUSIONS