Triggering B-physics with cylindrical pixel arrays

With the intent of studying a first level trigger capability, we performed a Monte Carlo simulation of 1.8 TeV p̄p interactions traversing three layers of silicon pixel detectors. We determined the efficiency for detection of the secondary vertices of B→π+π− decays while simultaneously rejecting minimum-bias events. The three layers were divided into 24 independent 15° sectors in φ (trial I) and 12 independent 30° sectors in φ (trial II). With the 24 sector arrangement, 78% of the events containing a B→π+π− decay yielded fewer than 140 triplets (one “hit” in each barrel) in any sector. In the 12 sector arrangement only 50% of the B→π+π− events have fewer than 140 triplets per sector. Minimum-bias events produced fewer triplets per sector. Simple linear equations were used to define selection criteria to suppress minimum-bias events by a factor of 100 000 while retaining 7.3% of the B→π+π− events in the 24 φ-sector arrangement and 5.6% of the B→π+π− events in the 12 φ-sector arrangement. The B yield can be increased at the cost of reducing the minimum-bias rejection factor.