The Search for an Axion-Like Particle as a Mediator for Dark Matter with the ATLAS Detector at the LHC

A phenomenological model of an axion-like particle (ALP) acting as a mediator to dark matter is introduced. The potential sensitivity to this particle in the ATLAS detector is assessed by analyzing simulated events of ALPs production for masses of 20, 40, and 60 GeV. The ALP is produced in association with a high transverse momentum photon in proton-proton collisions at 14 TeV of center-of- mass energy and 3000 fb−1 of integrated luminosity.  We considered the ALP decays to b bbar.  The mass of the ALP is reconstructed from the b-jets and the muon from B-meson decay is used as a trigger in conjunction with the high transverse momentum photon. A parameterized machine learning model is trained and applied to discriminate signal events produced by the ALP from background events produced by Standard Model processes. Though the overall significance of the signal is found to be under 1σ , the machine learning model roughly doubles the significance at ma = 20 GeV.