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The LHCb Readout System and Real-Time Event Management
Alessio F., Barandela C., Brarda L., Callot O., Frank M. et al
Dans IEEE Transactions on Nuclear Science - 16th IEEE/NPSS Real-Time Conference, Beijing : Chine (2009) - http://hal.in2p3.fr/in2p3-00477738
Informatique/Architectures Matérielles
The LHCb Readout System and Real-Time Event Management
F. Alessio1, C. Barandela1, L. Brarda1, O. Callot2, M. Frank1, J.-C. Garnier1, D. Galli, C. Gaspar1, Z. Guzik, E. van Herwijnen1, R. Jacobsson1, B. Jost1, A. Mazurov1, G. Moine1, N. Neufeld1, M. Pepe-Altarelli1, A.S. Varela1, R. Schwemmer1, P. Somogyi1, D. Sonnick1, R. Stoica1
1 :  CERN - European Organization for Nuclear Research
2 :  LAL - Laboratoire de l'Accélérateur Linéaire
CNRS : UMR8607 – IN2P3 – Université Paris XI - Paris Sud
Centre Scientifique d'Orsay B.P. 34 91898 ORSAY Cedex
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. In this paper, we will give an overview of the readout system, and describe the real-time event management and the experience with the system during the commissioning phase with cosmic rays and first LHC beams.

Communications avec actes
IEEE Transactions on Nuclear Science

16th IEEE/NPSS Real-Time Conference

LAL 09-305
LHCb – readout control – readout system – real time event management