Search for boosted low-mass resonances decaying into hadrons produced in association with a photon in pp collisions at √s = 13 TeV with the ATLAS detector

Abstract

Many extensions of the Standard Model, including those with dark matterparticles, propose new mediator particles that decay into hadrons. This paper presents asearch for such low mass narrow resonances decaying into hadrons using 140 fb-1 of protonprotoncollision data recorded with the ATLAS detector at a centre-of-mass energy of 13TeV.The resonances are searched for in the invariant mass spectrum of large-radius jets withtwo-pronged substructure that are recoiling against an energetic photon from initial stateradiation, which is used as a trigger to circumvent limitations on the maximum data recordingrate. This technique enables the search for boosted hadronically decaying resonances in themass range 20-100 GeV hitherto unprobed by the ATLAS Collaboration. The observed dataare found to agree with Standard Model predictions and 95% confidence level upper limits areset on the coupling of a hypothetical new spin-1 Z' resonance with Standard Model quarksas a function of the assumed Z'-boson mass in the range between 20 and 200 GeV.