DOI: 10.17182/hepdata.146899.v1/t3
title: "Table 3" of "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"

description: Summary of the impact of the systematic uncertainties on the $t\bar{t}\gamma$ production fiducial inclusive cross-section in the single-lepton and dilepton channels and their combination grouped into different categories. The quoted relative uncertainties are obtained by repeating the fit, fixing a set of nuisance parameters of the sources corresponding to each category to their post-fit values, and subtracting in quadrature the resulting uncertainty from the total uncertainty of the nominal fit. The total uncertainty is different from the sum in quadrature of the components due to correlations among nuisance parameters.
description: CERN-LHC-ATLAS. Inclusive and differential cross-sections are measured at particle level for the associated production of a top-quark pair and a photon ($t\bar{t}\gamma$). The analysis is performed using an integrated luminosity of 140 fb$^{−1}$ at a centre-of-mass energy of 13 TeV collected using the ATLAS detector. The measurements are performed in the single-lepton and dilepton top-quark pair decay channels focusing on $t\bar{t}\gamma$ topologies where the photon is radiated from an initial-state parton or one of the top quarks. The photon transverse momentum differential distribution is used to set limits on effective field theory parameters related to the electroweak dipole moments of the top quark. The combined limits using the photon and the $Z$-boson transverse momentum measured in $t\bar{t}$ production in associations with a $Z$ boson are also set.

 The fiducial region in single-lepton (dilepton) channel is defined as:
- Exactly one (two) electron or muon with p$_{\text{T}} &gt; 25$ GeV and $|\eta| &lt; 2.5$ which do not originate from hadron decays. Events are rejected if there are additional leptons with $p_{ ext{T}} &gt; 7$ GeV.
- Exactly one photon with E$_{\text{T}} &gt; 20$ GeV and $|\eta| &lt; 2.37$, and the sum of transverse momenta of all charged particles surrounding the photon within $\Delta R = 0.2$ is less than 5% of its own p$_\text{T}$.
- $\geq$ four (two) jets, which have p$_{\text{T}} &gt; 25$ GeV and $|\eta| &lt; 2.5$. Jets are clustered with the anti-$k_t$ algorithm with a radius parameter of $R = 0.4$. All stable particles are considered in the clustering, except for the selected electrons, muons and photons, and the neutrinos originating from the top quarks.
- $\geq$ 1 b-tagged jet. A jet is identified as a b-jet if a hadron with p$_T &gt; 5$ GeV containing a b-quark is matched to the jet through a ghost-matching method.
- Muons and electrons within $\Delta R &lt; 0.4$ from a jet are excluded. 
- Jets within $\Delta R = 0.4$ of an isolated photon candidate are excluded. 
- Events must satisfy $\Delta R(\gamma,l) &gt; 0.4$, where $l$ is the electron or muon.
 
 The full likelihood is provided for both inclusive and differential cross-section measurements in pyhf [1] JSON format and HS3[2] JSON format.
[1] pyhf format: https://github.com/scikit-hep/pyhf 
[2] HS3 format: https://github.com/hep-statistics-serialization-standard/hep-statistics-serialization-standard/tree/master