Measurement of the inclusive isolated prompt photon cross section in $pp$ collisions at $\sqrt{s} = 8$ TeV with the ATLAS detector

TL;DR

This paper reports a precise measurement of the inclusive isolated prompt photon production cross section in proton-proton collisions at 8 TeV, covering a wide energy range and comparing results with QCD predictions.

Contribution

It provides the first detailed measurement of the prompt photon cross section at 8 TeV with extensive kinematic coverage and data-driven background subtraction, enhancing understanding of QCD processes.

Findings

Measured cross sections agree with QCD calculations within uncertainties.

Extended the energy range of prompt photon measurements up to 1500 GeV.

Validated the background subtraction technique using calorimeter shower-shape variables.

Abstract

A measurement of the cross section for the inclusive production of isolated prompt photons in proton-proton collisions at a centre-of-mass energy of $\sqrt{s} = 8$ TeV is presented. The measurement covers the pseudo rapidity ranges $|\eta^{\gamma}| < 1.37$ and $1.56 \leq |\eta^{\gamma}| < 2.37$ in the transverse energy range $25 < E_{\rm T}^{\gamma} < 1500$ GeV. The results are based on an integrated luminosity of 20.2 fb$^{-1}$, recorded by the ATLAS detector at the LHC. Photon candidates are identified by combining information from the calorimeters and the inner tracker. The background is subtracted using a data-driven technique, based on the observed calorimeter shower-shape variables and the deposition of hadronic energy in a narrow cone around the photon candidate. The measured cross sections are compared with leading-order and next-to-leading order perturbative QCD calculations and are found to be in a good agreement over ten orders of magnitude.