Title: The CMS Electromagnetic Calorimeter at the LHC


The detectors at the Large Hadron Collider are now starting to take data (cosmics for now !). The Electromagnetic calorimeter of the CMS is a high resolution crystal calorimeter designed to detect electrons and photons, most particularly to search for a standard model Higgs to gamma gamma signal . I will describe the design, construction and the challenges of using this device to do physics at the LHC.