New preshower detector for the DIRAC experiment

Abstract The Preshower (PSh) detector [1] is a component of the DIRAC setup [2] . It is designed to identify and reject the huge e − e + pairs background in the ππ and Kπ pairs measurement produced in a hadronic atom ionization process. In the high energy region used for kaon detection, the small Nitrogen Cherenkov detector has low electron rejection efficiency. To increase the overall efficiency, a new two-layer scintillator Preshower detector has been developed and built. The new Preshower–Cherenkov combination ensures an electron rejection efficiency better than 99% in the momentum range 1–7 GeV/c.