Measurement of isolated-photon plus two-jet production in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

TL;DR

This paper measures the production of isolated photons with two jets in proton-proton collisions at 13 TeV using the ATLAS detector, comparing results with various QCD predictions to test theoretical models.

Contribution

It provides detailed measurements of photon plus two-jet production cross sections and compares them with state-of-the-art QCD predictions, highlighting areas of agreement and discrepancy.

Findings

NLO QCD predictions generally match data in shape and normalization.

Discrepancies observed in high invariant mass and rapidity separation regions.

Measurements cover photon transverse momenta from 150 GeV to 2 TeV.

Abstract

The dynamics of isolated-photon plus two-jet production in $pp$ collisions at a centre-of-mass energy of 13 TeV are studied with the ATLAS detector at the LHC using a dataset corresponding to an integrated luminosity of 36.1 fb$^{-1}$. Cross sections are measured as functions of a variety of observables, including angular correlations and invariant masses of the objects in the final state, $\gamma+jet+jet$. Measurements are also performed in phase-space regions enriched in each of the two underlying physical mechanisms, namely direct and fragmentation processes. The measurements cover the range of photon (jet) transverse momenta from 150 GeV (100 GeV) to 2 TeV. The tree-level plus parton-shower predictions from SHERPA and PYTHIA as well as the next-to-leading-order QCD predictions from SHERPA are compared with the measurements. The next-to-leading-order QCD predictions describe the data adequately in shape and normalisation except for regions of phase space such as those with high values of the invariant mass or rapidity separation of the two jets, where the predictions overestimate the data.