A ring imaging Cherenkov detector, the DELPHI barrel RICH prototype: Part B: Experimental studies of the detector performance for particle identification

Abstract

We present in this part B of the DELPHI Barrel RICH Prototype studies, a test beam investigation of the detector performance for particle identification. The tests have been done with both a proximity focused radiator of 1 cm of liquid perfluoro-hexane C 6F 14 and a focusing gas radiator of isobutane (50 cm mirror focal length). In the accompanying paper, part A, are given a technical description of the Prototype, the single photoelectron detector response and the spatial resolution attainable which are used throughout this article. The results show that the Prototype performance predicted by Monte Carlo simulations, as a function of the drift distance z d and the particle incidence angle θ b, have been achieved (particle identification between 0.17 and 35 GeV/ c). The calculations use the known and measured properties of the detector components which have been discussed throughout parts A and B. The single photon Cherenkov angle resolution obtained at z d = 0 drift distance is 8.5 mrad and 4.5 mrad for the liquid and the gas (at θ b = 0°) radiators respectively, as expected from the design. The numbers of detected photoelectrons in the images are 21 and 12 which correspond to a detector merit factor N 0 of 53 cm −1 and 77 cm −1 for the liquid and gas radiators respectively. These numbers are in agreement with the calculations but are limited because of the actual multiwire photoelectron detector performance. We show that N 0 = 65 cm −1 and 96 cm −1 are achievable for the liquid and gas radiators respectively. These last figures include a 90% cathode strip readout efficiency (third measurement coordinate for parallax correction) but no correction for dead space between drift volumes (liquid images only) and electronic dead time.