Isolated-photon production in polarized pp collisions

TL;DR

This paper presents a comprehensive NLO analysis of isolated prompt photon production in polarized pp collisions at RHIC energies, comparing isolation methods and exploring implications for gluon density measurements.

Contribution

It introduces a fully consistent NLO calculation for polarized prompt-photon production using a new isolation criterion that excludes fragmentation contributions.

Findings

The new isolation prescription reduces theoretical uncertainties.

Predictions show sensitivity to polarized gluon densities.

The study assesses the reliability of perturbative calculations for photon observables.

Abstract

We perform a detailed study of the production of isolated prompt photons in polarized hadronic collisions, in the centre-of-mass energy range relevant to RHIC. We compare the results obtained for a traditional cone-isolation prescription, with those obtained by imposing an isolation condition that eliminates any contribution to the cross section from the fragmentation mechanism. The latter prescription will allow us to present the first fully consistent next-to-leading order calculation in polarized prompt-photon production. We will discuss the theoretical uncertainties affecting the cross section, addressing the issue of the reliability of the perturbative expansion, for both inclusive isolated-photon and photon-plus-jet observables. Finally, we will study the dependence of our predictions upon the polarized parton densities, and the implications for the measurability of the gluon density.