A HIGH-PT TRIGGER FOR THE HERA-B EXPERIMENT

We have constructed a high-pT trigger for the HERA-B experiment at DESY. The HERA-B experiment produces B mesons by inserting wire targets into the halo of the proton beam circulating in HERA. The high-pt trigger records events that contain tracks that have high transverse momentum with respect to the beam. Such a trigger is efficient for recording B → π+π-, B → K- π+, Bs → K+ K-, , and other topical hadronic B decays. These decays provide sensitivity to the internal angles alpha and gamma of the CKM unitarity triangle, and they also can be used to measure or constrain the mixing parameter xs.