Performance of the CMS Endcap Muon detectors

In the Compact Muon Solenoid (CMS) Experiment, muon detection in the forward direction is accomplished by Endcap Muon system which is comprised of 468 Cathode Strip Chambers (CSCs). These detectors identify muons, provide a fast muon trigger, and give a measurement of the muon trajectory. In this paper, we present results of the detector performance analyses based on the data collected during the Magnet Test and Cosmic Challenge (MTCC) exercise conducted by the CMS experiment in 2006. About 8% of the full system (36 CSCs) operated for a few months and collected cosmic ray data. We show that CMS CSCs identify two-dimensional trigger primitives with a 99.9% efficiency. These segments, found by the CSC electronics after the passing of a muon through the chambers, are the input information for the Level-1 muon trigger and, also, are a necessary condition for chambers to be read out by the Data Acquisition System (DAQ). The spatial resolution per chamber is measured to be around 100 – 200 μ m . In contrast to the earlier studies based on a total detector area typically limited to 0.01 m 2 (efficiency) and 3 m 2 (resolution), results presented in this report were obtained for many installed CSCs operating in situ over an area of 20 m 2 (efficiency) and 60 m 2 (spatial resolution).