Test beam results from the CMS electromagnetic calorimeter

A precision lead tungstate crystal calorimeter is being constructed by the CMS collaboration. As a key part of the future CMS detector at the LHC, the electromagnetic calorimeter will play a major role in probing electroweak symmetry-breaking and searches for new physics. In order to check that the required performance of the electromagnetic calorimeter is attainable, every prototype is tested in real conditions within a beam of particles. In 2003 two modules of the electromagnetic calorimeter featuring the final mechanical design and electronic architecture have been tested with two different versions of the front-end electronics. In this paper a review of the main results of test beam campaigns in 2002 and 2003 are given.