LHCb silicon: VELO and inner tracker

The LHCb experiment contains two sub-detectors consisting of silicon microstrip detectors, the Vertex Locator (VELO) and the Inner Tracker. The VELO is placed around the interaction region, with the silicon sensors within 7 mm of the LHC beams. It is designed to perform a precision measurement of production and decay vertices of B-mesons. The sensors have to be operated in a hostile radiation environment due to the proximity of the beams. Prototype silicon sensors of both n-on-n and p-on-n technology have been irradiated and characterised in a test-beam. The efficiencies of the prototypes are compared. The results motivate the choice of n-on-n sensors for the VELO. The Inner Tracker is part of a tracking system using two detector technologies, with silicon microstrip sensors close to the LHC beam, and straw tubes further away from the beam. Inner Tracker prototype sensors with large pitch were designed and produced. Test- beam results on resolution, signal-to-noise ratio and efficiency are discussed. It was found the efficiency has a strong dependency on the geometry of the sensor. (5 refs).