Search for dark matter in association with an energetic photon in pp collisions at s√=13 TeV with the ATLAS detector

A search for dark matter is conducted in final states containing a photon and missing transverse momentum in proton-proton collisions at 13 TeV. The data, collected during 2015-2018 by the ATLAS experiment at the CERN LHC, correspond to an integrated luminosity of 139 fb-1. No deviations are observed relative to the predictions of the Standard Model. The results are interpreted as exclusion limits in models where weakly interacting dark-matter candidates are pair-produced via an axial-vector or a vector mediator in the s-channel. Results are also expressed in terms of 95% confidence level limits on the parameters of a model with an axion-like particle produced in association with a photon.