The LHCb Muon System: Electronics commissioning and results from first data taking

The electronics of the LHCb Muon System consists of about 1400 chambers (MWPC and 3 GEM) distributed in five stations and 122,000 readout channels giving space and time information about the passage of the particles. The hits given by the System are input to the L0 Muon trigger, which processes them and gives its decision within a maximum latency time of 4 μs. We describe the techniques and procedures for the commissioning of the LHCb Muon System electronics. Special emphasis is given to systematic connectivity tests and timing alignment procedures. Our system tools allow the relative alignment of the Muon hits not only to the correct LHC Bunch Crossing cycle (25 ns), but also inside it, using the information of the detector time distributions, which are obtainable with a resolution of about 2 ns. The precise alignment has been performed and then checked exhaustively in data taking runs acquiring cosmic rays, triggered by the L0 Muon and Calorimeter Triggers, both independently and together. We present the results obtained.