Test Beam Results on the Performance of the CMS Electromagnetic Calorimeter

The performance of the CMS electromagnetic calorimeter has been studied with the test beam data recorded with a fully equipped barrel super-module. An efficient method for signal amplitude reconstruction has been implemented and tested on these data. Results on energy resolution and electronics noise show excellent performance of the apparatus. Effects associated to shower containment in crystal arrays were investigated and a set of corrections has been formulated and used to provide results on energy resolution.