This post reports a finding (as of Aug. 14) related to the TPC T0 from the HFT-TPC matching using the cosmic ray data. Some early relavant posts from Mustafa can be found here
https://drupal.star.bnl.gov/STAR/blog/mstftsm/t0-using-hft-run14-new-tpc-alignment

Here I tried two runs:  15051001 and 15088054, both were taken at RFF field. The initial T0 fine-tuning and HFT-TPC global alignment obtained from FF (150400XX) data were included here (see Mustafa's post above).

	15051001	15088054
IST-TPC
PXL-TPC

The above plots show run 15088054 residuals look reasonable (some small shift can be fine-tuned later). But we see there is a significant global T0 offset in run 15051001 (~1cm level).

I compared the log files from two runs and saw the following difference:

run#15051001

run#15088054

---------------------------------------------------------------------------------------

LoadTable: .L /afs/rhic.bnl.gov/star/packages/DEV/StarDb/Conditions/trg/trgTimeOffsetB.20140311.001107.C

StTpcDbMaker:WARN  - [[33mSt_trgTimeOffsetC::instance found table trgTimeOffsetB with NRows = 1 in db[[0m

StTpcDbMaker:WARN  - [[33mValidity:20140311/1107 -----   20380101/0[[0m

 

 ---------------------------------------------------------------------------------------

 bfc/.make/db/.const/StarDb/Conditions/trg/.trgTimeOffsetB/trgTimeOffsetB  Allocated rows: 1     Used rows: 1    Row

 Table: trgTimeOffset_st             [0] :

 ======================================================================================

float   offset            2.4001 : standard trigger offset in micro-seconds

float   laserOffset        1.469 : laser trigger offset in micro-seconds

float   laserOffsetW      0.0429 : laser extra trigger offset for West laser

---------------------------------------------------------------------------------------

The ~0.2 micron-second difference seem to count for the 1cm offset.  

Checking the $STAR/StarDb/Conditions/trg/ directory, it looks like most trgTimeOffset in Run14 are 2.4. The 2.18 values only appear in some very short of periods: e.g. set to 2.18 at 0140101.000115 and re-set to 2.40 at 20140101.000715. Similarly for other days, but on day 20140220, there is only one entry setting the value to 2.18 and no resetting shortly afterwards. Is there because of a missing reset table?

I made a copy of this table set to a name of trgTimeOffsetB.20140220.001107.C and put in local StarDb directory

 row.offset         =   2.18147349 + 0.2186; //2.1815;//     2.05; // standard trigger offset in micro-seconds  ;

and the outcome is:

 

	15051001 with new trgTimeOffsetB table
IST-TPC
PXL-TPC