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

The Level-1 Muon Barrel Trigger is one of the main elements of the event selection of the ATLAS experiment at the Large Hadron Collider. Its input stage consists of an array of processors receiving the full granularity of data from Resistive Plate Chambers in the central area of the ATLAS detector ("Barrel"). The trigger efficiency and the level of synchronisation of its elements with the rest of ATLAS and the LHC clock are crucial figures of this system: many parameters of the constituent RPC detector and the trigger electronics have to be constantly and carefully checked to assure a correct functioning of the Level-1 selection. Notwithstanding the complexity of such a large array of integrated RPC detectors, the ATLAS Level-1 system has resumed operations successfully after the past 2 year shutdown, with levels similar to those of Run 1. We present the inclusive monitoring of the RPC+L1 system that we have developed to characterise the behaviour of the system, using reconstructed muons in events selected by alternate triggers. Our method has allowed us to study the performance on the 2015 data in detail and relate L1 performance with single RPC element conditions in regions nearby; and their evolution with time. We illustrate the selections, strategy and validation for an unbiased determination of the efficiency and timing of the RPC and the L1 from data; and show the results we obtain and that are fed back into the ATLAS simulation to model real data.