The ATLAS Barrel Level-1 Muon Trigger Calibration

The ATLAS experiment uses a system of three concentric Resistive Plate Chambers detectors layers for the level-1 muon trigger in the air-core barrel toroid region. The trigger classifies muons within different programmable transverse momentum ranges, and tags the identified tracks with the corresponding bunch crossing number. The algorithm looks for hit coincidences within different detector layers inside the programmed geometrical road which defines the transverse momentum cut. The on-detector electronics providing the trigger and detector readout functionalities collects input signals coming from the RPC front-end. Because of the different time-of-flights and cables and optical fibres lengths, signals have to be adjusted in time in order to be correctly aligned before being processed. Programmable delay logics are provided in the trigger and readout system to allow for time adjustment, for hit signals as well as for LHC Timing, Trigger and Control signals. The trigger calibration provides the set of numbers used during electronics initialization for correctly aligning signals inside the trigger and readout system. The functionality scheme and the algorithm of the calibration are presented.