Mainz 2012 – scientific programme

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HK: Fachverband Physik der Hadronen und Kerne

HK 11: Instrumentation

HK 11.6: Talk

Monday, March 19, 2012, 18:00–18:15, P 2

ALICE TRD GTU Online Tracking and Trigger Performance in recent p-p and Pb-Pb Collisions — •Felix Rettig, Stefan Kirsch, and Volker Lindenstruth — Frankfurt Institute for Advanced Studies, Johann Wolfgang Goethe-Universtät, Frankfurt

The Transition Radiation Detector of the ALICE experiment at the LHC is designed to provide fast trigger contributions based on an online reconstruction of charged tracks with high transverse momentum.

Within about 4 microseconds after a collision, a total of 1.2 million analog channels is scanned for short track segments by more than 65,000 custom multi-chip modules in the front-end electronics. The parametrizations of these segments are transferred to the Global Tracking Unit (GTU) at up to 2.2 TBit/s.

The GTU is a massively parallel low-latency computing system consisting of 109 dedicated high-performance FPGA-based nodes. 90 nodes in the input layer perform a full 3D reconstruction and momentum calculation for high-momentum tracks. 18 middle layer nodes and one top-layer node then infer various Level-1 trigger contributions about 6 microseconds after the collision.

Presented here is a performance analysis of the online tracking in p-p as well as Pb-Pb collisions over the past two years of LHC operation. Selected trigger algorithms based on the online tracking are outlined.