Nuclear Effects in Prompt Photon Production at the Large Hadron Collider.pdf

a r X i v : h e p - p h / 0 1 0 1 0 4 1 v 2 2 4 S e p 2 0 0 1 Nuclear effects in prompt photon production at the Large Hadron Collider J. Jalilian-Marian1,2, K. Orginos1,3 and I. Sarcevic1 1Department of Physics, University of Arizona, Tucson, Arizona 85721 2Physics Department, Brookhaven National Laboratory, Upton NY 11973-5000 3RIKEN-BNL Research Center, Brookhaven National Laboratory, Upton NY 11973-5000 Abstract We present a detailed study of prompt photon production cross section in heavy- ion collisions in the central rapidity region at energy of √ s = 5.5 TeV, appropri- ate to LHC experiment. We include the next-to-leading order radiative corrections, O(αemα 2 s), nuclear shadowing and the parton energy loss effects. We find that the nuclear effects can reduce the invariant cross section for prompt photon production by an order of magnitude at pt = 3 GeV. We discuss theoretical uncertainties due to parton energy loss and nuclear shadowing parameters. We show that the K-factor, which signifies the importance of next-to-leading order corrections, is large and has a strong pt dependence. 1 Introduction There has been a considerable theoretical and experimental interest in studying photon production in heavy-ion collisions at BNL’s Relativistic Heavy Ion Collider (RHIC) and CERN’s Large Hadron Collider (LHC) energies [1]. Photons produced in heavy-ion colli- sions provide an excellent probe of the properties of the dense matter, such as the quark- gluon plasma or the hot hadronic gas, produced after the collision. Due to the small cross sections of electromagnetic interactions, photons can escape the strongly interacting matter produced in the collision without further interactions. Studying photon production at the RHIC and LHC energies is of special interest, as it has been suggested as an elegant signal for detecting the formation of a quark gluon plasma (QGP) in heavy-ion collisions [2]. However, photons can be produced at different stages of the heavy i