Measurement of the Production Cross Section of Pairs of Isolated Photons with CMS

TL;DR

This paper reports on the measurement of isolated photon pair production cross sections at 7 TeV with CMS, comparing results to NLO pQCD predictions and highlighting areas of discrepancy in specific phase space regions.

Contribution

First measurement of photon pair production cross sections at 7 TeV with detailed comparison to NLO pQCD predictions.

Findings

Integrated cross sections agree with theory

Discrepancy observed at small photon angles

Highlights need for improved theoretical models

Abstract

In this paper we present the measurement of the integrated and differential production cross sections of pairs of prompt isolated photons in proton-proton collisions at a centre-of-mass energy of 7 TeV with the Compact Muon Sollenoid (CMS) detector at the Large Hadron Collider (LHC). A next-to-leading order (NLO) perturbative QCD (pQCD) prediction was compared to the measurement, which was performed on a sample corresponding to an integrated luminosity of 36 inverse picobarn. While the agreement on integrated cross sections is satisfactory, a discrepancy is observed in the region of the phase space populated by photons with small relative angle, where the theoretical prediction underestimates the measured cross section.