A PROGRESS REPORT ON THE DEVELOPMENT OF THE CSI-RICH DETECTOR FOR THEALICE EXPERIMENT AT LHC

The particle identification in ALICE (A Large Ion Collider Experiment) at LHC will be achieved by two complementary systems based on time-of -flight measurement, at low p(t), and on the Ring Imaging Cherenkov (R ICH) technique, at p(t) ranging from 2 to 5 GeV/c, respectively. The H igh Momentum PID (HMPID) system will cover similar to 5% of the phase space, the single-arm detector array being composed by seven 1.3 x 1.3 m(2) CsI-RICH modules placed at 4.7 m from the interaction point wher e a density of about 50 particles/m(2) is expected. A 1 m(2) prototype , 2/3 of HMPID module size, has been successfully tested at the CERN/P S beam where 18 photoelectrons per event have been obtained with 3 GeV /c pions and 10 mm liquid C6F14 radiator. Mechanical problems related to the liquid radiator vessel construction have been solved and the pr ototype, fully equipped, will be tested at the CERN/SPS to investigate the PID capability in high particle density events. In this report, a fter an introductory discussion on the requirements for PID in ALICE, the HMPID prototype is described and the main results of beam tests on large area CsI photocathodes, operated in RICH detectors, are even. ( C) 1998 Elsevier Science B.V. All rights reserved.