The CHAOS Fast Trigger An array of telescopes for e, π and p mass identification in the intermediate energy region

Abstract The CHAOS Fast Trigger (CFT) is a system of 20 telescopes of plastic scintillator and lead-glass detectors, designed for the discrimination of charged e, π, p (and d) particles in the momentum range 40 to 400 MeV/ c for e and π, and from 200 to 800 MeV/ c for p. The results from a test measurement performed at TRIUMF show that the π-p and the π-e discrimination efficiency (i.e. the percentage of particles identified) is > 99% and > 90% in the whole momentum range, respectively. The π-e discrimination efficiency has been improved to > 93% through the application of neural networks.