Pattern recognition techniques of charged hadron identification with HMPID at LHC

Abstract

The High Momentum Particle Identification Detector (HMPID), already installed in the ALICE setup at LHC, is ready to identify charged hadrons with momentum up to 5 GeV/ c. It consists of seven modules of a RICH detector with a CsI photocathode. The HMPID will operate to identify charged hadrons both in Pb–Pb collisions and in p–p collisions. The strategy to identify charged hadrons will differ according to the colliding system. In the case of central Pb–Pb collisions, the identification of Cherenkov photons requires efficient pattern recognition algorithm (based on a modified Hough transform, that maps the pad coordinate space directly to the Cherenkov angle parameter space). In the first p–p collisions, instead, where the tracking has to be optimized (or even missing, as sometimes in the cosmic runs), a first reconstruction step based on a new algorithm (Hidden Track Algorithm—HTA) will be used. The tracking parameters are not used in the pattern recognition, at the end an estimate of the track direction as well as the mean 〈 θ C 〉 will be performed. The HTA will be here described and preliminary results on its performances will be presented.