Measurement of the production cross section of pairs of isolated photons in $pp$ collisions at 13 TeV with the ATLAS detector

The collaboration
CERN-EP-2021-105, 2021.

Abstract (data abstract)
Measurement of inclusive production cross section of pairs of isolated prompt photons with the ATLAS Detector at centre-of-mass energy 13 TeV.The transverse momentum of the photons is required to be greater than 40(30) GeV for the (sub)leading photon. The photons are required to be seperated by more than $\Delta R > 0.4$. The photons are required to be isolated with $E_\mathrm{T}^\mathrm{iso}<0.09\cdot p_{\mathrm{T},\gamma}$. The isolation energy $E_\mathrm{T}^\mathrm{iso}$ is defined as the scalar sum of the transverse momenta of particles in a cone of $\Delta R < 0.2$ around the photon and is corrected for the transverse momentum density of jets in the event.For each differential cross section measurement 100 data bootstrap replicas are provided in the resources which should be used to estimate the statistical uncertainty and the correlations between different observables. For convenience the statitistical uncertainties are also contained in the main tables.The systematic uncertainties can be considered fully correlated and seperate up-and down-variations are provided. Sometimes the up-and down-variations have the same sign. The uncertainties need to be symmetrized before calculating chi2 values.