Performance of the MWPC of the first station of the LHCb Muon System

The LHCb Muon System is composed of five detection stations (M1-M5) equipped with a total of 1368 Multi-Wire Proportional Chambers (MWPC) and 12 triple-GEM based detectors. The first station (M1) is placed upstream of experiment calorimeters and thus is equipped with very ¿light¿ MWPC made by only two gas-gaps (instead of four) and with triple-GEM based detectors. The chambers have to provide a high detection efficiency, a fast response and a good space resolution. For the first time the performance of different M1 MWPC completely equipped with the final Front-End Electronics, have been tested with cosmic rays. The detection efficiency, the time resolution and the hit multiplicity were measured. Chambers with anode-wire-readout and with cathode-pad-readout were tested and the results are compared. The results obtained will be used to individuate the optimized working conditions of the apparatus and to make a more realistic detector description in the LHCb Monte Carlo simulation.