Performance of ATLAS RPC Level-1 muon trigger during the 2015 data taking

Abstract

RPCs are used in the ATLAS experiment at the LHC for the muon trigger system in the barrel region, which corresponds to a pseudorapidity range of |η|<1.05. The status of the system during the 2015 data taking is presented, including measurements of the RPC detector efficiencies and of the trigger performance. The RPC system has been active in more than 99.9% of the ATLAS data taking, showing very good reliability. The RPC detector efficiencies were close to Run 1 and to design values. The trigger efficiency for the high-pT thresholds used in single-muon triggers has been approximately 4% lower than in Run 1, mostly because of chambers disconnected from HV due to gas leaks. Two minor upgrades have been performed in preparation of Run 2 by adding the so-called feet and elevator chambers to increase the system acceptance. The feet chambers have been commissioned during 2015 and are included in the trigger since the last 2015 runs. Part of the elevator chambers are still in a commissioning phase and will probably need a replacement at the end of 2016.