Hadron identification with the HERMES RICH.
on behalf of the HERMES collaboration
University of Gent,Proeftuinstraat 86, 9000 Gent, Belgium
March 29, 2002
The HERMES experiment has upgraded its spectrometer in 1998 with a ring imaging Cerenkov (RICH) detector to allow the identification of pions, kaons and protons over practically the entire momentum range of HERMES, by using two radiators, silica aerogel and
C4F10 gas. The identification of the different hadrons in the HERMES RICH detector is based on two different methods: the indirect ray tracing method (IRT) and the direct ray tracing method (DRT). Both methods use a likelihood analysis to select the most probable particle type. The IRT and DRT method exist in parallel; a decision network chooses the optimal method for a certain event topology. The efficiencies and contaminations for particle identification have been experimentally determined by the use of decaying Φ,
Ks and Λ particles.