Defined plateau region Knee 95% WP=knee+150V RPC operation and Hardware Performance  Annual HV module recalibration – all CAEN A3512N HV module offsets recalibrated  No current drift in the Endcap RPC after the lowering of the UXC environmental Temperature  The average RPC chamber current per wheel or disk is lower than 3 µA for high luminosity beams.  Number of RPC operated in Single Gap mode is unchanged in 2011: 6 in the Barrel and 20 in the Endcap  Number of active electronic channels is very stable ~ 98.5%  A dedicated HV scan was performed to identify the working point (WP) of each RPC roll and each HV channel  Additional Pressure correction is foreseen to be implemented next TS in order to compensate the P-variations  Stable and Reliable performance of RPC detector during the CMS operation - No RPC DEAD time during recent CMS operation, only 2 RPC problems have caused a downtime to CMS data taking! HV scan fit ε(HV) = ε max /(1 + e Slope (HV-HV50%) )

RPC Trigger Performance  In 2011 the RPC Trigger Efficiency has improved due to:  New 3/6 RPC PAC trigger algorithm: in the barrel at least 3 out of 6 available layers are required to be fired in order a muon candidate to be generated. 4 layers were required in  efficiency in the barrel increased  Improved geometrical acceptance: The optical links were rearranged to obtain better geometrical coverage in the gap region between RB0 and RB+/- 1  additional increase of the efficiency in the |  | ~0.3  The Entire Online Software was migrated from XDAQ to Trigger Supervisor  Front-end Electronics Threshold Configuration from database  HSCP trigger enabled: The PAC is now able to trigger “slow” particles, which reach the muon system in the next BX. It looks for the coincidence of hits in two consecutive BX, the candidate BX is determined by the BPTX trigger veto. Offline muon p T > 8GeV/c Offline muon p T > 8GeV/c Offline muon p T > 7GeV/c Offline muon p T > 7GeV/c L1 RPC Trigger Efficiency including detector geometrical acceptance and hit efficiency vs L1 CSC or DT trigger

RPC Detector Performance SF6 problem + HV scan Very Stable Performance after RUN All RPC chambers working at a fixed applied HV: HV endcap = 9550 Volts All RPC chambers working at a fixed applied HV: HV barrel = 9350 Volts Data taken during the HV scan are analysed and used to define the HV settings per individual HV channel. SF6 problem + HV scan 20 April May April 2011