Final calibration results of CMS electromagnetic calorimeter photodetectors

The Compact Muon Solenoid is one of two generic detectors currently being constructed for the Large Hadron Collider at CERN foreseen to begin data taking in 2007. The electromagnetic calorimeter consists of a barrel and endcaps. These are made of PbWO4 scintillating crystals. In the barrel, the scintillation signal is read out by Hamamatsu avalanche photodiodes, connected in parallel in a structure called a “capsule”. Each of the 61,200 channels must be equipped with a capsule, the reliability of which must be assured since they will be inaccessible during the life of the experiment. The capsule production is now finished. We present the final calibration and performance statistics.