ALICE TRD GTU tracking and trigger performance with first data

The Transition Radiation Detector of the ALICE experiment is designed to provide fast trigger contributions for different signature classes as well as full event information for offline analysis. A total of 1.2 million analog channels is processed massively parallel in more than 65 000 multi-chip modules of the front-end electronics. Pattern matching algorithms are applied to find and parametrize short stiff track segments. Up to several thousand track segments are transferred to the second stage, the Global Tracking Unit (GTU), via 1 080 optical fibres. The GTU consists of 109 dedicated FPGA-based processing nodes forming a three-level hierarchy. 90 Track Matching Units perform online 3D track reconstruction and momentum calculation based on the track segments within 1.2 μs. Track information is then forwarded to 18 Supermodule Units for trigger computation. The top-level Trigger Generation Unit finally delivers the overall TRD trigger contributions within 6 μs after the collision. A first analysis of the online tracking performance of the GTU with early data taken at the LHC and a comparison to detailed hardware simulations is presented. The performance of first implementations of a single high-pt particle trigger as well as a jet trigger is evaluated.