The LHCb Readout System and Real-Time Event Management

The LHCb Experiment is a hadronic precision experiment at the LHC accelerator aimed at mainly studying b-physics by profiting from the large b-anti-b-production at LHC. The challenge of high trigger efficiency has driven the choice of a readout architecture allowing the main event filtering to be pe...

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Bibliographic Details
Published in:IEEE transactions on nuclear science 2010-04, Vol.57 (2), p.663-668
Main Authors: Alessio, F, Barandela, C, Brarda, L, Callot, O, Frank, M, Garnier, J.-C, Galli, D, Gaspar, C, Guzik, Z, van Herwijnen, E, Jacobsson, R, Jost, B, Mazurov, A, Moine, G, Neufeld, N, Pepe-Altarelli, M, Varela, A Sambade, Schwemmer, R, Somogyi, P, Sonnick, D, Stoica, R
Format: Article
Language:English
Subjects:
Architecture
Calibration
Centralized control
Computer architecture
Computer programs
Control systems
Event detection
Farms
Information filtering
Information filters
Large Hadron Collider
LHCb
Management
readout control
readout system
real time event management
Real time systems
Software
Software performance
Streams
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Summary:The LHCb Experiment is a hadronic precision experiment at the LHC accelerator aimed at mainly studying b-physics by profiting from the large b-anti-b-production at LHC. The challenge of high trigger efficiency has driven the choice of a readout architecture allowing the main event filtering to be performed by a software trigger with access to all detector information on a processing farm based on commercial multi-core PCs. The readout architecture therefore features only a relatively relaxed hardware trigger with a fixed and short latency accepting events at 1 MHz out of a nominal proton collision rate of 30 MHz, and high bandwidth with event fragment assembly over Gigabit Ethernet. A fast central system performs the entire synchronization, event labelling and control of the readout, as well as event management including destination control, dynamic load balancing of the readout network and the farm, and handling of special events for calibrations and luminosity measurements. The event filter farm processes the events in parallel and reduces the physics event rate to about 2 kHz which are formatted and written to disk before transfer to the offline processing. A spy mechanism allows processing and reconstructing a fraction of the events for online quality checking. In addition a 5 Hz subset of the events are sent as express stream to offline for checking calibrations and software before launching the full offline processing on the main event stream.
ISSN:0018-9499
1558-1578
DOI:10.1109/TNS.2010.2042069