The LHCb Muon System

The ability to provide fast muon triggering and efficient offline muon identification is an essential feature of the LHCb experiment. The muon detector is required to have a high efficiency over a large area and an appropriate time resolution to identify the bunch crossing for level–0 triggers. The LHCb muon detector consists of five stations equipped with 1368 Multi Wire Proportional Chambers and 12 Gas Electron Multiplier chambers. The technical design of the chambers is briefly presented and the Quality Control procedures during the various construction steps are described. The method developed for gas gain uniformity measurement is also described together with the results on efficiency of detectors fully equipped with the front–end electronics, obtained from tests with cosmic rays.