The use of the TT1 tracking station in the level-1 trigger

We present the algorithms that form the basis of an efficient (mini-)Level-1 trigger: the VELO tracking including primary vertex finding, TT1 tracking and matching to VELO track seeds, with determination of the transverse momentum, and finally a simple decision logic based on the impact parameters and transverse momenta of two selected tracks in the event. For the TT1 tracking station, two implementations are considered, a straw-tube/silicon hybrid version and a full-silicon design. The inclusion of the TT1 tracking station improves dramatically the Level-1 trigger performance with respect to the algorithm described in the Technical Proposal. We arrive at the conclusion that a full-silicon implementation of this tracking chamber performs significantly better than the hybrid version.