Barrel Muon System Background Simulation of the CMS TDR Design.pdf

Available on CMS information server CMS NOTE 1998/052 The Compact Muon Solenoid Experiment Mailing address: CMS CERN, CH-1211 GENEVA 23, Switzerland CMS Note June 1998 Barrel Muon System Background Simulation of the CMS TDR Design A. Benvenuti and V. Genchev ) INFN, Bologna, Italy Abstract Backgrounds from punchthrough particles originating from minimum bias events and inclusive QCD jets in the CMS barrel muon system has been simulated using a detailed GEANT description of the Technical Design Report geometry and shielding. Rates due to punchthrough in the entrance at each muon station as well as rates of hits, produced by these punchthrough particles, are given as a function of Z-axis of the muon chambers. The origin of punchthrough hits are presented which may be used to optimise the muon chamber performance. ) On leave from INRNE, Sofia, Bulgaria 1 Introduction The muon system receives background hits from neutrons and from charged particles which can affect the muon chamber design, trigger performance, pattern recognition and reconstruction . In the more of published papers concerning with the punchthrough fluxes in the CMS muon system a simplified structure of detector elements consisting of average materials was used. The rates of particles reaching the muon system are found to be very high. At some values of  they range from 0.1 to 1 - 2 kHz/cm2. These punchthrough particles are only candidates for producing background hits in the muon chambers. The relevant issue is what frac- tion of these particles will produce hits in the muon stations. In this work we present results for the punchthrough rates as well as the rates of hits, produced by these punchthrough particles. 2 CMS model and data sample The CMS simulation program CMSIM, version 114, which includes the detailed description of the TDR version of the CMS detectors =1;2;3;4;5= and best version of the CMS shielding =6= was used. The critical region of the CMS detector concerning punchthrough is the ba