The CMS Resistive Plate Chambers system-detector performance during 2011

Resistive Plate Chambers are used in the CMS experiment to provide a dedicated muon trigger both in barrel and endcap. About 3000 m(2) of double gap RPCs have been produced and have been installed in the experiment. The RPC system has been studied with millions of muons coming from LHC collisions during 2011. Making use of the redundant muon system composed by Drift Thbes (DT) in the barrel and Cathode Strip Chambers (CSC) in the endcaps that provide independent tracking and trigger informations, the performance of the RPCs has been studied in terms of efficiency, cluster size, spatial resolution and noise rate. Moreover during this long period of detector operations the stability of the system has been monitored to study the relevant detector parameters as a function of time.