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

Summary form only. The authors discuss a study to upgrade the existing H1 tracking detector by a semiconductor backward tracking telescope consisting of eight beam concentric discs to measure the gluon and quark distribution functions at very low Bjorken x. Each disc comprises three planes of strip and pad silicon detectors made of 4-in wafers in order to measure the polar angle and the transverse momentum, and to trigger on deep inelastically scattered electrons. The technical and electronics design of the trigger has to cope with very high beam background rates and the HERA bunch crossing rate of 10.4 MHz.<>