Measurements of inclusive and differential cross-sections of $t\bar{t}\gamma$ production in $pp$ collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

TL;DR

This paper reports precise measurements of the production rates and properties of top quark pairs with an associated photon in proton-proton collisions at 13 TeV, using ATLAS data, to test the Standard Model and probe new physics.

Contribution

It provides the first detailed differential cross-section measurements of $tar{t}\gamma$ production at 13 TeV, including constraints on top quark electroweak dipole moments.

Findings

Measured differential cross-sections for photon, lepton, and jet kinematics.

Photon transverse momentum distribution constrains top quark dipole moments.

Results are consistent with Standard Model predictions.

Abstract

Cross-section measurements of the associated production of a top quark pair and a photon ($t\bar{t}\gamma$) are performed with an integrated luminosity of 140 fb$^{-1}$ of proton-proton collisions at a centre-of-mass energy of 13 TeV collected by the ATLAS detector at the LHC. The measurement focuses on $t\bar{t}\gamma$ topologies where the photon is radiated from an initial-state parton or one of the top quarks. The differential cross-sections are measured for variables characterising the photon, lepton and jet kinematic properties. The distribution of the photon transverse momentum is used to constrain effective field theory operators related to the electroweak dipole moments of the top quark.