1. January 28, 2008 CLAS12 Software Meeting Mac Mestayer How SDA Does Tracking - Mac Mestayer Written by Bogdan Niczyporuk in 1990’s Structure of the software: –calls, information passing Sequence of calls (what info. req’d when?) –begin run, event time –within event (cluster, segment, link, hbt, lramb, tbt) Example: calculation of doca from time the ‘Trees’ –cluster, segment finding, linking –swimming –hbt and tbt

2. January 28, 2008 CLAS12 Software Meeting Mac Mestayer Sequence of Tracking find ‘clusters’ and ‘segments’ –clusters are ‘blobs’, segments are possible track segments within a cluster (see ana_segm.F) link segments into a track candidate –lookup table: input is 3 segment locations, output is track viability and estimators for track parameters (see ana_link) fit to wire positions alone –allows matching to outer detector, improvement of parms. calculate doca’s from times resolve l-r ambiguities fit to doca’s (swim, fit, invert matrix for better parms., repeat)

3. January 28, 2008 CLAS12 Software Meeting Mac Mestayer

4. Flowchart of trk_event_tbt; routine which does the time-based tracking

5. January 28, 2008 CLAS12 Software Meeting Mac Mestayer

6. Flowchart of sda_swim; routine which swims a trajectory through the various detector planes and fills a bank with, e.g. doca from the track to the nearest wire

7. January 28, 2008 CLAS12 Software Meeting Mac Mestayer

8. Flowchart of trk_dcam; routine which returns the distance-of-closest-approach as calculated from the wire’s drift-time

9. January 28, 2008 CLAS12 Software Meeting Mac Mestayer Room for improvement allow more than one hit per layer –very common, will simplify l-r amb. segment-finding is very complicated and flawed by the requirement of only one hit per layer build in noise-reduction routines which eliminate spurious hits, also look for out-of-time tracks do linking from ‘quietest’ area (reg. 2?) use hit-based tracks to initiate l-r amb., etc.