Efficiency of finding muon track trigger primitives in CMS cathode strip chambers

Abstract In the Compact Muon Solenoid(CMS) experiment, muondetection in the forward direction is accomplished by cathode strip chambers (CSC). These detectors identify muons, provide a fast muontrigger, and give a precise measurement of the muontrajectory. There are 468 six-plane CSCs in the system. The efficiency of finding muontrigger primitives ( muontrack segments) was studied using 36 CMS CSCs and cosmic ray muonsduring the Magnet Test and Cosmic Challenge (MTCC) exercise conducted by the CMS experiment in 2006. In contrast to earlier studies that used muonbeams to illuminate a very small chamber area ( 0.01 m 2 ), results presented in this paper were obtained by many installed CSCs operating in situ over an area of ≈ 23 m 2 as a part of the CMS experiment. The efficiency of finding two-dimensional trigger primitives within six-layer chambers was found to be 99.93 ± 0.03 % . These segments, found by the CSC electronics within 800 ns after the passing of a muonthrough the chambers, are the input information for the Level-1 muontrigger and, also, are a necessary condition for chambers to be read out by the Data Acquisition System.