Performance of a LVL2 Trigger Feature Extraction Algorithm for the Precision Tracker.

An algorithm to search for isolated high pT tracks in the ATLAS precision tracker suitable for use in the LVL2 trigger is described. A histogramming method employing a Hough transform is used to select sets of points forming track candidates. For each selected set of points, fits are performed to all combinations of one point per detection plane. The best candidate is chosen on the basis of the fit residuals. The algorithm has been implemented in the t2scFex package of the ATRIG trigger simulation program and also for benchmarking studies in a stand-alone program SCTFEX. Efficiency, fake track rate and timing measurements are presented for a number of algorithm options.