Tracking at LVL2 with IDScan
IDScan is a complete package for fast pattern recognition in the Silicon Trackers of ATLAS (Pixel+SCT), suitable for all tracking purposes at the LVL2 Trigger. IDScan takes as inputs 3-D space points from the Pixel and SCT detectors and proceeds sequencially, in four algorithmic steps:
The z-finder
The z-finder determines the z-position of the interesting pp interaction, prior to any track reconstruction. Details can be found here.The hit filter
Given the z-position of the interesting pp interaction, the hit filter selects groups of space points by requiring consistency in (eta,phi). Details can be found here.The group cleaner
The above groups may contain space point from more than one tracks and/or some noise. The group cleaner splits large groups to individual track candidates and removes some wrongly accepted space points.The track fitter
The track candidates are then verified by the track fitter which calculates track parameters and their errors.IDScan has many strengths and has been recently used for extracting the results for the ATLAS HLT-DAQ-DCS Techincal Design Report, which can be found here.