M. Bocker,
M. Adams,
P. Bechtle,
P. Buchholz,
C. Cruse,
U. Husemann, E. Klaus,
N. Koch,
M. Kolander,
I. Kolotaev,
H. Riege,
J. Schutt,
B. Schwenninger,
R. van Staa,
D. Wegener
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ABSTRACT: One of the main goals of the HERA-B experiment at DESY in Hamburg,
Germany, is to study the properties of B-mesons with the emphasis on CP
violation. B-mesons are produced in hadronic interactions of a 920-GeV
proton beam with an internal wire target. An effective bunch crossing
rate of about 8.5 MHz leads to about 200 charged tracks per event.
Therefore, a highly selective and efficient trigger system providing
high suppression of background events is required. The HERA-B trigger
system consists of four levels. A rate reduction factor of 200 is aimed
at by the first-level trigger (FLT). The muon pretrigger system, as a
part of the FLT, is a modular system consisting of about 100 large-size
VME modules of three different types: the pretrigger link board (PLB),
the pretrigger coincidence unit (PCU), and the pretrigger message
generator (PMG). The data rate processed by the pretrigger system is
about 19.5 GByte/s. The PLBs process digitized hit information in eight
independent electronic channels in parallel. Every electronic channel
handles 32 bits of hit information received from the front-end driver
buffer system. Optical links operating at 800 Mb/s transmit the data
after serialization to PCUs, which calculate coincidences using complex
programmable logic devices. The PMGs transform this coincidence
information into messages for the FLT processors. The concept and design
as well as results of the muon pretrigger running at HERA-B are
presented
IEEE Transactions on Nuclear Science 09/2001; · 1.45 Impact Factor
