First results on the CMS RPC system using the 2007 and 2008 cosmic ray data

A preliminary study of the performance of the CMS RPC system will be here presented. A large set of muons have been triggered and reconstructed using cosmic ray data taken in the 2007 and 2008 CMS Global Runs. The Drift Tube chambers and the RPC chambers have both been used as trigger system and the data have been used to measure detector and trigger performances. RPC detector and trigger efficiencies have been measured using muon data triggered by DT chambers only in order to have an unbiased set of data. More studies on the RPC detector have been performed (noise, current, cluster size) and the first results will also be shown here.