RICH detectors for the LHCb experiment

The LHCb experiment is being designed to study CP violation in the B- meson system. It differs from other LHC experiments in its requirement for an excellent pi /K separation in the momentum range 1-150 GeV/c. This is accomplished by two RICH counters: RICH1 has a 5 cm-thick aerogel radiator and a 95 cm-long C/sub 4/F/sub 10/ radiator, while RICH2 has a 180 cm-long CF/sub 4/ radiator. Cherenkov photons are focused by spherical mirrors onto photodetectors. Three photodetector options are under study: a 127 mm diameter hybrid pad photodiode (HPD) with a 2048 Si pad sensor and analog readout, a 80 mm diameter pixel HPD with a 1024-pixel Si sensor and binary readout, and Hamamatsu's multianode photomultiplier (MaPMT). Recent test beam results on the performance of both RICH and photodetector prototypes show good agreement with the design. Cherenkov ring pattern recognition based on a global log-likelihood method is being developed to satisfy the hadron identification requirements. (10 refs).