Measurements of $Z\gamma+$jets differential cross sections in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

TL;DR

This paper presents detailed measurements of the differential cross sections for Z gamma production with jets at 13 TeV, comparing results with various Standard Model predictions to test their accuracy in describing complex hadronic events.

Contribution

It provides the first comprehensive differential cross-section measurements of Z gamma plus jets at 13 TeV with full Run 2 data, including comparisons with multiple theoretical models.

Findings

Good agreement with MATRIX and MiNNLO_PS predictions

Discrepancies observed in some soft radiation regions

Validates the accuracy of current QCD calculations for Z gamma processes

Abstract

Differential cross-section measurements of $Z\gamma$ production in association with hadronic jets are presented, using the full 139 fb$^{-1}$ dataset of $\sqrt{s}=13$ TeV proton-proton collisions collected by the ATLAS detector during Run 2 of the LHC. Distributions are measured using events in which the $Z$ boson decays leptonically and the photon is usually radiated from an initial-state quark. Measurements are made in both one and two observables, including those sensitive to the hard scattering in the event and others which probe additional soft and collinear radiation. Different Standard Model predictions, from both parton-shower Monte Carlo simulation and fixed-order QCD calculations, are compared with the measurements. In general, good agreement is observed between data and predictions from MATRIX and MiNNLO$_\text{PS}$, as well as next-to-leading-order predictions from MadGraph5_aMC@NLO and Sherpa.