A silicon backward tracking detector and trigger for the H1 experiment at the ep collider HERA

A proposal is described to upgrade the existing H1 tracking detector by a semiconductor backward tracking telescope consisting of 8 beam-concentric disks to measure the gluon and quark distribution functions at very low Bjorken x. Each disk comprises three planes of strip and pad silicon detectors made of 4-in wafers in order to determine the polar angle and the transverse momentum, and to trigger on deep inelastically scattered electrons. The simulation work and the layout constraints on the semiconductors are discussed. The technical and electronics design of the trigger is reviewed. It has to cope with very high beam background rates and the HERA bunch crossing rate of 10.4 MHz. >