Particle identification using plastic scintillators in the COMET Phase-I experiment

The COMET (COherent Muon to Electron Transition) Phase-I experiment aims to search for muon to electron conversion with a single event sensitivity of O (10−15). In COMET, a Cylindrical Trigger Hodoscope (CTH), consisting of segmented plastic scintillators, provides a primary trigger signal and timing measurement while suppressing backgrounds under the high rate environment. This paper studies the particle identification capability of CTH to suppress one of the serious backgrounds induced by cosmic-rays. We demonstrated that a background suppression factor greater than 10 is achievable with a signal efficiency higher than 90%.