Measurement of the inclusive isolated-photon production cross section in pp collisions at $\sqrt{s}$ = 13 TeV

TL;DR

This paper reports the measurement of inclusive isolated photon production cross sections in proton-proton collisions at 13 TeV, extending the kinematic range to lower transverse momenta and providing data for testing perturbative QCD predictions.

Contribution

It presents the first measurement of isolated photon cross sections at 13 TeV covering lower pT and xT ranges, with improved precision and comparison to theoretical models.

Findings

Measurement agrees with NLO pQCD calculations.

Extends photon measurements to lower pT and xT.

Provides data for future QCD studies.

Abstract

The production cross section of inclusive isolated photons has been measured by the ALICE experiment at the CERN LHC in pp collisions at centre-of-momentum energy of $\sqrt{s}=13$ TeV collected during the LHC Run 2 data-taking period. The measurement is performed by combining the measurements of the electromagnetic calorimeter EMCal and the central tracking detectors ITS and TPC, covering a pseudorapidity range of $|\eta^{\gamma}|<0.67$ and a transverse momentum range of $7<p_{\rm T}^{\gamma}<200$ GeV/$c$. The result extends to lower $p_{\rm T}^{\gamma}$ and $x_{\rm T}^{\gamma} = 2p_{\rm T}^{\gamma}/\sqrt{s}$ ranges, the lowest $x_{\rm T}^{\gamma}$ of any isolated photon measurements to date, extending significantly those measured by the ATLAS and CMS experiments towards lower $p_{\rm T}^{\gamma}$ at the same collision energy with a small overlap between the measurements. The measurement is compared with next-to-leading order perturbative QCD calculations and the results from the ATLAS and CMS experiments as well as with measurements at other collision energies. The measurement and theory prediction are in agreement with each other within the experimental and theoretical uncertainties.