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 π/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 C4F10 radiator, while RICH2 has a 180 cm-long CF4 radiator. Cherenkov photons are focused by spherical mirrors onto photodetectors. Three photodetector options are under study: a 127 mm diameter Pad Hybrid Photodiode (HPD) with a 2048 silicon pad sensor and analog readout, a 80 mm diameter Pixel HPD with a 1024-pixel silicon sensor and binary readout, and Hamamatsuʹs 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.