Centrality dependence of inclusive prompt photon production in d+Au, Au+Au, p+Pb, and Pb+Pb collisions

TL;DR

This paper calculates how the production of prompt photons varies with collision centrality in various nuclear collisions at RHIC and LHC, finding minimal medium effects at high transverse momentum but potential measurable effects at low pT.

Contribution

It introduces calculations of centrality dependence of prompt photon production using the EPS09s nuclear PDFs, aligning well with experimental data and suggesting limited medium modification effects.

Findings

Good agreement with PHENIX and CMS data

High-pT photon production minimally affected by medium

Possible measurable centrality effects at low pT

Abstract

We calculate the centrality dependence of the midrapidity nuclear modification for inclusive prompt photon production in d+Au and Au+Au collisions at RHIC and in p+Pb and Pb+Pb collisions at the LHC. Our results, using the recent spatially dependent nuclear PDF set EPS09s, are consistent with the existing high-pT data from the PHENIX and CMS collaborations. The good agreement even in the case of nucleus+nucleus collisions suggests that the high-pT direct photon production is not significantly altered by the strongly interacting medium produced in such collisions. We find the centrality dependence of the nuclear modifications generally rather weak but perhaps measurable at low pT.