Inclusive prompt photon production in nuclear collisions at RHIC and LHC

TL;DR

This paper provides NLO calculations of inclusive prompt photon production in nuclear collisions at RHIC and LHC, exploring nuclear modifications and their potential to probe nuclear parton distribution functions and quark-gluon plasma effects.

Contribution

It offers detailed NLO predictions for prompt photon production using various nPDF sets, highlighting their differences and potential for constraining nuclear PDFs and hot nuclear matter effects.

Findings

Different nPDF sets yield significantly different predictions.

Prompt photon R_AA can gauge cold and hot nuclear matter effects.

Predictions suggest prompt photons as probes for quark-gluon plasma.

Abstract

Nuclear modification factors of inclusive prompt photon production in d-Au collisions at RHIC and p-Pb collisions at the LHC are provided at different rapidities. The calculations are performed at NLO accuracy using the EPS09 NLO nuclear parton distribution functions (nPDFs) and their error sets. The results are compared to the ones obtained with the nDS and HKN07 NLO nPDFs, and to the corresponding nuclear modification factors of neutral pion production in these collisions. The sensitivity of these results to the scale choice is also investigated. Interestingly, the predictions using the different nPDF sets differ from each other to the extent that this observable can be expected to become very useful for probing nPDFs over a wide range of Bjorken-x. In order to obtain a perturbative QCD baseline in heavy-ion collisions, calculations are carried out for minimum bias Au-Au collisions at RHIC and Pb-Pb collisions at the LHC. We also estimate the maximal possible suppression which the produced QCD matter can be expected to have on inclusive prompt photon production due to the quenching of the fragmentation component. The nuclear modification factor for prompt photon production is thus suggested to be used for gauging both the cold and the hot nuclear matter effects on other hard processes which are expected to be affected by quark-gluon plasma formation, such as large-pT hadron and jet production.