Drift velocity


Below is some documentation for the current automated drift velocity calibration. There is also documentation on another possible drift velocity calibration technique.


----- Automated processing of Fast Offline files -----

Automatic calibration is run using three scripts under $STAR/StRoot/macros/calib:

  • LoadLaserDriftVelocityToDb.csh
  • LoopOverLaserTrees.C
  • LoadLaserDriftVelocityToDb.C

The shell script is run as a cron job every 6 hours (for now, stdout of this job goes to ~starreco/AutoCalib.log), grouping together *.laser.root files produced by the BFC chain "LanaDVtpx,ITTF,CorrX,OSpaceZ2,OGridLeak3D" for each DAQ run. The search for *.laser.root files looks in the FastOffline output file directories by default (/star/data{09,10,11,12}/reco/) and excludes zero field runs by path name, preventing their calibration - this is important because their drift velocity would likely be different, while reconstruction interpolates between values in the database and would experience interference between field on/off entries if not properly accounted. Note that FastOffline-produced files will have BFC logs in a standard location as well, such as /star/rcf/prodlog/dev/log/daq/st_laser_*.log.gz The grouped *.laser.root files are processed by LoopOverLaserTrees.C to yield a database table ready for upload. The shell script moves these tables around and then runs LoadLaserDriftVelocityToDb.C to upload them. The table files have names like tpcDriftVelocity.[timestamp].C.

Because an individual run may result in files which finish Fast Offline production in different 6 hour blocks, the shell script will attempt to group any new files together with previously found ones for a run, and run the macros again to determine a more statistically precise drift velocity. Such recalibration includes deactivating the previous database entry as the new entry is uploaded.

----- Output files from automated processing of Fast Offline files -----
Files from the automated dv calculations are in the directory /star/data10/calib/tpcDriftVelocity/. There you will find files like listOfLaserMacros[date].list, which are lists of the table files to upload from a given occasion [date] of running the shell script.

There are three types of subdirectories:

runs: copies of the laser.root files produced by Fast Offline containing the TTrees of laser information

Load[date]: The Done subdirectory contains the tpcDriftVelocity.[timestamp].C files that were successfully loaded into the db. Others subdirectory contains those that were not selected for some reason (deprecated). Failed contains files that failed for some reason (db access error, etc.).

Check[date] (deprecated): These subdirectories contain runs to check. Badrun contains files that were flagged as bad for some reason. VarSel contains files that were selected but not entered into the db for some reason (too close in time to another run?) and VarOth contains files that were not selected to be put into VarSel.

Output from Runs 9-15 have all been archived to HPSS at /home/genevb/Calibrations/DriftVelocity/RunXXX.tar where XXX is the Run Year.