Tübingen 2003 – wissenschaftliches Programm
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HK: Physik der Hadronen und Kerne
HK 4: Instrumentation und Anwendungen I
HK 4.3: Vortrag
Montag, 17. März 2003, 16:30–16:45, C
Identifying ET ≥ 100 GeV Jets with the ALICE High Level Trigger — •Constantin Loizides — IKF, University of Frankfurt
One interesting observable at ALICE will be the measurement of the inclusive jet cross section at 100 to 200 GeV transversal jet energy around θ=π/2, and the jet fragmentation function; both to be compared to pp.
The expected rate of jets with ET ≥ 100 GeV in central Pb-Pb is around 1 to 9000 in the reduced TPC acceptance of ∣ η ∣ < 1/2. The central detectors of the ALICE experiment at LHC will produce a data size of up to 75 MByte/event at an event rate <200 Hz resulting in a data rate of 15 GByte/sec. This exceeds the foreseen mass storage bandwidth of 1.25 GByte/sec by a factor of 15. Online processing of the data is necessary in order to select interesting (sub)events (”High Level Trigger”), or to compress data efficiently by modeling techniques.
The HLT system is a massive parallel computing system located in the data flow after the front-end electronics of the detector and before the event-builder of the DAQ. Most of the local pattern recognition will be done using the FPGA co-processor while the data is being transferred to the memory of the corresponding nodes. Algorithms for conventional cluster finding and local track finding based on a Circle Hough Transformation of the raw data are currently under development.
Latest results concerning both the C++ and the VHDL implementation of the online tracking code, as well as simulated jet trigger efficiencies on Pythia and Hijing data for 100 GeV jets will be shown.