Berlin 2005 – wissenschaftliches Programm

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HK: Physik der Hadronen und Kerne

HK 22: Postersitzung

HK 22.82: Poster

Montag, 7. März 2005, 16:30–18:00, TU MA141

2nd Level Trigger Performance in HADES — •Camilla Gilardi, Ingo Fröhlich, and Tiago Pérez — II. Physikalisches Institut, University of Gießen, Heinrich-Buff-Ring 16, 35392 Gießen

The main purpose of the HADES spectrometer at GSI Darmstadt is the measurements of dilepton decays of light vector mesons. Since the amount of unbiased data would be relatively high, it could not be stored without the employ of an online selective mechanism which allows an enhancement of the signal-to-background ratio. The first level trigger system (LVL1) selects the most central collisions, while the second level trigger (LVL2) searches signatures of dilepton decays first as leptons candidates in the RICH, TOF and Pre-shower detector. In order to select events with lepton pairs, the LVL2 trigger performs pattern recognition to find lepton signatures (through the Image Processing Units - IPUs), and combines the position and angle information for each of these signatures into tracks (through the Matching Unit - MU). In the last year, a lot of progress has been achieved to increase the performance of the LVL2 trigger. In particular the distribution system of the LVL1 and LVL2 signals has been reimplemented. Furthermore, the time-of-flight IPU was improved to gain in speed and flexibility, allowing to read out generic modules like scaler and latches. This work has been supported by BMBF, GSI and the DFG.