Conference Paper

Design and performance of the level 1 calorimeter trigger for the BABAR detector

Dept. of Phys., Imperial Coll. of Sci., Technol. & Med., London
DOI: 10.1109/NSSMIC.2000.949930 Conference: Nuclear Science Symposium Conference Record, 2000 IEEE, Volume: 2
Source: IEEE Xplore


Since May 1999 the BABAR detector has been taking data at the
PEP-II asymmetric electron-positron collider at the Stanford Linear
Accelerator Center, California. This experiment requires a very large
data sample and the PEP-II accelerator uses intense beams to deliver the
high collision rates needed. This poses a severe challenge to the BABAR
trigger system, which must reject the large rate of background signals
resulting from the high beam currents whilst accepting the collisions of
interest with very high efficiency. One of the systems that performs
this task is the Level 1 Calorimeter Trigger, which identifies energy
deposits left by particles in the BABAR calorimeter. It is a digital,
custom, fixed latency system which makes heavy use of high-speed FPGA
devices to allow flexibility in the choice of data filtering algorithms.
Results from several intermediate processing stages are read out,
allowing the selection algorithm to be fully analysed and optimized
offline. In addition, the trigger is monitored in real time by sampling
these data and cross-checking each stage of the trigger calculation
against a software model. The design, implementation, construction and
performance of the Level 1 Calorimeter Trigger during the first year of
BABAR operation are presented

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