27 September 2004 to 1 October 2004
Interlaken, Switzerland
Europe/Zurich timezone

The ALICE High Level Trigger

29 Sep 2004, 14:20
20m
Jungfrau (Interlaken, Switzerland)

Jungfrau

Interlaken, Switzerland

oral presentation Track 1 - Online Computing Online Computing

Speaker

M. Richter (Department of Physics and Technology, University of Bergen, Norway)

Description

The ALICE experiment at LHC will implement a High Level Trigger System, where the information from all major detectors are combined, including the TPC, TRD, DIMUON, ITS etc. The largest computing challenge is imposed by the TPC, requiring realtime pattern recognition. The main task is to reconstruct the tracks in the TPC, and in a final stage combine the tracking information from all detectors. Based on the physics observables selective readout is done by generation of a software trigger (High Level Trigger), capable of selecting interesting (sub)events from the input data stream. Depending on the physics program various prosessing options are currently being developed, including region of interest processing, rejecting events based on software trigger and data compression schemes. Examples of such triggers are verification of candidates for high-pt dielectron heavy-quarkonium decays, momentum filter to enhance the open-charm signal, high-pt jets selection etc. Technically the HLT system entails a very large scale processing farm with about 1000 active processors. The input data stream is designed for 25 GB/sec. The system nodes will be interfaced to the local data concentrators of the DAQ system via optical fibers receiving a copy of the raw data. The optical fibers will be connected to the PCI-bus of HLT nodes using a custom PCI card. These cards provide a co-processor functionality for the first steps of the pattern recognition. The talk will give an overview of the HLT project and will focus on the latest results regarding efficient data compression and trigger performance.

Primary authors

A. Vestbo (Department of Physics and Technology, University of Bergen, Norway) A. Wiebalck (Kirchhoff Institute for Physics, University of Heidelberg, Germany) B. Skaali (Department of Physics, University of Oslo, Norway) C. Loizides (Institute for Nuclear Physics, University of Frankfurt, Germany) D. Rohrich (Department of Physics and Technology, University of Bergen, Norway) H. Helstrup (Faculty of Engineering, Bergen University College, Norway) H. Tilsner (Kirchhoff Institute for Physics, University of Heidelberg, Germany) K. Ullaland (Department of Physics and Technology, University of Bergen, Norway) M. Richter (Department of Physics and Technology, University of Bergen, Norway) R. Stock (Institute for Nuclear Physics, University of Frankfurt, Germany) T. Alt (Kirchhoff Institute for Physics, University of Heidelberg, Germany) T. Vik (Department of Physics, University of Oslo, Norway) T.M. Steinbeck (Kirchhoff Institute for Physics, University of Heidelberg, Germany) V. Lindenstruth (Kirchhoff Institute for Physics, University of Heidelberg, Germany)

Presentation Materials