CMS electromagnetic calorimeter performance and test beam results

Energy resolution of the CMS crystal electromagnetic calorimeter has been measured with an electron test beam using a fully equipped barrel supermodule. Both intrinsic energy resolution and energy resolution for electrons with quasi-uniform impact on the crystal surface are measured. The amplitude of the signal collected from crystals is reconstructed by a digital filtering technique and corrections for the position dependent response are applied in the case of quasi-uniform impact. The resolution measured for the supermodule is fully compatible with design expectations.