# Measurement of the inclusive isolated-photon cross section in $pp$ collisions at $\sqrt{s}=13$ TeV using 36 fb$^{-1}$ of ATLAS data

## TL;DR

This paper reports a precise measurement of the isolated-photon production cross section in proton-proton collisions at 13 TeV, comparing results with advanced QCD theoretical predictions to test the accuracy of current models.

## Contribution

First measurement of the differential isolated-photon cross section at 13 TeV with detailed comparison to NLO and NNLO QCD calculations.

## Key findings

- Predictions agree well with data within uncertainties.
- Provides constraints on proton parton distribution functions.
- Enhances understanding of photon production mechanisms in high-energy collisions.

## Abstract

The differential cross section for isolated-photon production in $pp$ collisions is measured at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC using an integrated luminosity of 36.1 fb$^{-1}$. The differential cross section is presented as a function of the photon transverse energy in different regions of photon pseudorapidity. The differential cross section as a function of the absolute value of the photon pseudorapidity is also presented in different regions of photon transverse energy. Next-to-leading-order QCD calculations from JETPHOX and SHERPA as well as next-to-next-to-leading-order QCD calculations from NNLOJET are compared with the measurement, using several parameterisations of the proton parton distribution functions. The predictions provide a good description of the data within the experimental and theoretical uncertainties.