Optimization of the missing transverse energy + photon triggers for the search of dark matter with Atlas Detector.

Considerable efforts have been dedicated in searches for dark matter particles at colliders such as the Large Hadron Collider (LHC). The Higgs portal could provide access to the dark and visible sector interactions. The DM photon (a.k.a dark photon γd) is a hypothetical particle that can be produced in the Higgs boson decay H→γγd. We consider the production of the Higgs boson (at the LHC) through the fusion of gluons (ggF) which has the largest production rate, while triggering events from the ggF H→γγd is very challenging given the relatively small missing transverse energy and the single photon. In this paper we aim to optimize the new missing energy plus photon trigger to filter out such events. Based on the analysis performed, a combination of missing transverse energy larger than 50, an isolated photon transverse momentum > 25 GeV, and Δφ (missing transverse energy, photon pT) > 1.8, shows an acceptance rate of 1% with reasonable event rate of 48 Hz. Further reductions of event rate are possible using more sophisticated missing transverse energy algorithms at the trigger level.