Study for a High Level Trigger for the Decay Channel Bs->Ds pi->Phi pi pi->K K pi pi

This note describes the use of the CMS Tracker in selecting the decay channel Bs->Ds pi->Phi pi pi->K K pi pi. Several combinations of a single muon trigger with jet triggers have been considered for Level-1. A proposed High Level Trigger algorithm is based on kinematical and topological properties of the Bs decay mode. The number of signal events collected during one year of low luminosity depends on the bandwidth dedicated for such kind of events at the Level-1 trigger. If an allocated Level-1 trigger rate would be 1 KHz the number of collected signal events will be about 300 for the integrated luminosity of 20 fb^-1. Such a rate will give an output on tape of 5 Hz. The use of a limited number of hits for track reconstruction allows to achieve an average time (normalised to a 1GHz Pentium III processor) for HLT decision of about 640 msec.