Measurement of the Differential Cross Section for Isolated Prompt Photon Production in pp Collisions at 7 TeV

TL;DR

This paper reports a measurement of the differential cross section for isolated prompt photon production in proton-proton collisions at 7 TeV, using CMS detector data, and compares results with QCD predictions.

Contribution

First measurement of isolated prompt photon cross section at 7 TeV with detailed pseudorapidity and energy dependence, validating perturbative QCD calculations.

Findings

Measured cross sections agree with NLO QCD predictions

Photon identification methods are complementary and effective

Data covers a broad energy and pseudorapidity range

Abstract

A measurement of the differential cross section for the inclusive production of isolated prompt photons in proton-proton collisions at a centre-of-mass energy of 7 TeV is presented. The data sample corresponds to an integrated luminosity of 36 inverse picobarns recorded by the CMS detector at the LHC. The measurement covers the pseudorapidity range |eta|<2.5 and the transverse energy range 25 < ET < 400 GeV, corresponding to the kinematic region 0.007 < xT < 0.114. Photon candidates are identified with two complementary methods, one based on photon conversions in the silicon tracker and the other on isolated energy deposits in the electromagnetic calorimeter. The measured cross section is presented as a function of ET in four pseudorapidity regions. The next-to-leading-order perturbative QCD calculations are consistent with the measured cross section.