Measurement of differential cross sections for the production of a pair of isolated photons in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports precise measurements of the differential cross sections for isolated photon pairs produced in proton-proton collisions at 7 TeV, comparing results with advanced QCD theoretical predictions.

Contribution

It introduces a data-driven isolation template method for extracting prompt diphoton yields and provides detailed differential cross sections at multiple QCD orders.

Findings

Measured cross section: 17.2 pb with uncertainties.

Differential cross sections as functions of mass, momentum, and angles.

Results agree with higher-order QCD predictions.

Abstract

A measurement of differential cross sections for the production of a pair of isolated photons in proton-proton collisions at sqrt(s) = 7 TeV is presented. The data sample corresponds to an integrated luminosity of 5.0 inverse femtobarns collected with the CMS detector. A data-driven isolation template method is used to extract the prompt diphoton yield. The measured cross section for two isolated photons, with transverse energy above 40 and 25 GeV respectively, in the pseudorapidity range abs(eta) < 2.5, abs(eta) not in [1.44,1.57] and with an angular separation Delta R > 0.45, is 17.2 +/- 0.2 (stat.) +/- 1.9 (syst.) +/- 0.4 (lum.) pb. Differential cross sections are measured as a function of the diphoton invariant mass, the diphoton transverse momentum, the azimuthal angle difference between the two photons, and the cosine of the polar angle in the Collins-Soper reference frame of the diphoton system. The results are compared to theoretical predictions at leading, next-to-leading, and next-to-next-to-leading order in quantum chromodynamics.