Measurement of isolated photon production in pp and PbPb collisions at sqrt(sNN) = 2.76 TeV

TL;DR

This study measures isolated photon production in proton-proton and lead-lead collisions at 2.76 TeV, finding results consistent with theoretical predictions and no significant nuclear modification effects across collision centralities.

Contribution

First measurement of isolated photon production in PbPb collisions at 2.76 TeV, comparing results with pp collisions and perturbative QCD predictions.

Findings

Photon spectra agree with NLO pQCD calculations.

PbPb to pp yield ratio is consistent with unity across centralities.

No significant nuclear modification observed.

Abstract

Isolated photon production is measured in proton-proton and lead-lead collisions at nucleon-nucleon centre-of-mass energies of 2.76 TeV in the pseudorapidity range |eta|<1.44 and transverse energies ET between 20 and 80 GeV with the CMS detector at the LHC. The measured ET spectra are found to be in good agreement with next-to-leading-order perturbative QCD predictions. The ratio of PbPb to pp isolated photon ET-differential yields, scaled by the number of incoherent nucleon-nucleon collisions, is consistent with unity for all PbPb reaction centralities.