The HERA-B transition radiation detector

The Transition Radiation Detector (TRD) is a part of the Electron Identification System of the HERA-B experiment, which is a study of CP violation in the B system. The TRD’s major role is the efficient identification of electrons and the rejection of hadrons in the central region, where the particle density is the highest. This paper describes the design and performance of the TRD which is based on a modern fine-grain structure – polypropilene fibre radiator with Kapton straw proportional detectors. The results from a prototype test of the TRD in the HERA proton beam are discussed and compared with extensive Monte Carlo (MC) simulations of the real HERA-B conditions.