Aad, G.Abbott, B.Abbott, D. C.Abed Abud, A.Abeling, K.Abhayasinghe, D. K.Çetin, Serkant Ali2024-07-182024-07-1820211029-8479https://doi.org/10.1007/JHEP11(2021)169https://hdl.handle.net/11411/7085A measurement of prompt photon-pair production in proton-proton collisions at root s = 13 TeV is presented. The data were recorded by the ATLAS detector at the LHC with an integrated luminosity of 139 fb(-1). Events with two photons in the wellinstrumented region of the detector are selected. The photons are required to be isolated and have a transverse momentum of p(T,gamma 1(2)) > 40 (30) GeV for the leading (sub-leading) photon. The differential cross sections as functions of several observables for the diphoton system are measured and compared with theoretical predictions from state-of-the-art Monte Carlo and fixed-order calculations. The QCD predictions from next-to-next-to-leadingorder calculations and multi-leg merged calculations are able to describe the measured integrated and differential cross sections within uncertainties, whereas lower-order calculations show significant deviations, demonstrating that higher-order perturbative QCD corrections are crucial for this process. The resummed predictions with parton showers additionally provide an excellent description of the low transverse-momentum regime of the diphoton system.eninfo:eu-repo/semantics/openAccessHadron-Hadron Scattering (Experiments)Photon ProductionProton-Proton ScatteringQcdParton DistributionsArticle2-s2.0-8512095933010.1007/JHEP11(2021)16911Q2Q1WOS:000728326100001