The Compact Muon Solenoid (CMS) electromagnetic calorimeter

The Electromagnetic Calorimeter of the CMS detector for the CERN Large Hadron Collider (LHC) is designed to allow the detection of a standard model Higgs boson of mass below 150 GeV. An overview is given of this homogeneous calorimeter made of almost 80 000 lead tungstate (PbWO4) 26X0 long crystals. This includes a description of the engineering design and a review of the different components of the calorimeter. The most recent results obtained in particle beams with realistic crystal prototypes are also presented.