The first-level trigger of the HERA-B experiment: Performance and expectations.

V. BALAGURA, M. BRUINSMA, H. FLECKENSTEIN, J. FLAMMER, J. GLASS, R. MANNER, A. MICHETTI, M. NORENBERG, R. PERNACK, V. POPOV, D. RESSING, I. RIU, A. SBRIZZI, B. SCHWINGENHEUER, A. SOMOV, U. UWER, H. WAHLBERG, A. WURZ

Novosibirsk, Russia

Conferencia; 8th International Conference on Instrumentation for Colliding Beam Physics (INSTR02); 2002

HERA-B is a fixed target spectrometer which uses 920 GeV protons incident on various target materials. The experiment is aimed to study various aspects of beauty and charm physics. The detector is designed to operate at high interaction rates with an average of 4–5 interactions per event. The First-Level Trigger (FLT) is required to reduce the input rate by more than two orders of magnitude while keeping high efficiency for beauty and charm channels. The trigger performs online track reconstruction and takes decisions based on particle momenta or pair masses. A pipeline architecture is implemented on about 100 pipelined hardware processors to perform this job. The working principle and first results of the FLT performance based on the data acquired during the run in the year 2000 are described.