Gamma ray background radiation for glass electrode RPCs in the CMS/LHC environment, estimation approach with GEANT4 Monte Carlo simulation packages

Abstract

Resistive plate chambers (RPCs) are gaseous parallel-plate detectors with good spatial and time resolution, which makes them very useful in high energy physics and astrophysics experiments. In the present study, glass plates are utilized as the electrodes in the construction of RPCs, these kinds of glass-RPCs are being used in many ongoing high energy physics experiments. In this paper, for the first time Monte Carlo simulation of 2 mm gas gap RPCs with glass electrodes have been performed with GEANT4 standard and low-energy packages. Gamma ray propagation through these RPCs with two types of sources, is discussed. We report measurements of the response of a glass RPC for gamma rays of energy in the range 0.1–1000.0 MeV. As expected glass electrode RPCs give higher sensitivity results than bakelite plates RPCs. The obtained results show a good agreement between GEANT4 standard and low-energy packages (showing ∼99% agreement for both low and high energy gamma rays). The evaluated results are applied to both endcap and barrel areas of CMS regions. According to these results, a hit rate of about 100, 50 and 30 Hz cm−2 is calculated using GEANT4 standard electromagnetic package for a 20×20 cm2 glass RPC in the ME1, ME2, and ME4 regions respectively. While for the same gamma source and GEANT4 package, a hit rate of about 0.46 and 1.40 Hz cm−2 was computed for the MB1 and MB4 stations respectively. Similar characteristics of hit rates have been observed for the GEANT4 low electromagnetic package.