The Pixel Hybrid Photon Detector of the LHCb RICH

The LHCb experiment at the CERN Large Hadron Collider employs two Ring Imaging Cherenkov (RICH) detectors for particle identification. The first covers the charged particle momentum range 1-60GeV/c using aerogel and C4F10 radiators and the second covers up to 100 GeV/c using CF4. Cherenkov light will be detected using a novel type of position sensitive device: the pixel Hybrid Photon Detector (HPD). In the pixel HPD, photoelectrons are produced in a multialkali photocathode, accelerated and focused by an electrostatic field, and then detected by a pixelated silicon detector which is bump-bonded onto a 40 MHz read-out chip. This paper reports on the development of the LHCb RICH detectors and the performance of the HPDs.