[clas12_rgk] Problem with CTOF in recent RG-K Runs

[Daniel Carman]

Folks,

I have been looking at the recently cooked RG-K runs in the range from 5681-5990. The calibrations in
place for RG-K were based on my calibrations for run 5700. Looking at the flight times for charged
tracks in CTOF, about a third of the counters have the wrong flight time as can be seen in the attached
plots. The physical flight times for charged particles should be in the range up to ~4 ns. However, in
the present data about 1/3 of the counters have unphysically large flight times (values > 5 ns). This is
due to a problem in the P2P calibration for these counters. These events with the wrong P2P show up
at beta~0.2 and give rise to the background in chi2pid underlying the peak about zero.

I expect this may be due to the fact that the data were calibrated before the DC geometry constants
were shifted and the cooked data include the DC geometry constants. This affects the path length
and hence the ST determination. If these changes, it can affect the CTOF timing. I am looking into
this.

For now, I am proceeding by not using chi2pid or the EB PID assignment and doing my own PID.
I compute the TOF for CTOF shifting any flight times>4.5 ns by TRF and everything looks good for
all 48 CTOF counters. This is just an FYI for folks looking into this data. Let me know if you have
any questions. See the attached plots for more information.

Regards,
Daniel

***********************************************************************************
*                                                                                                                  *
* Dr. Daniel S. Carman                  e-mail : carman at jlab.org<mailto:carman at jlab.org>                     *
* Staff Scientist                              office : (757)-269-5586                         *
* Jefferson Laboratory                   web: http://userweb.jlab.org/~carman  *
*                                                                                                                  *
***********************************************************************************


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/clas12_rgk/attachments/20190410/ed55473c/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: rgk-issues-1.pptx
Type: application/vnd.openxmlformats-officedocument.presentationml.presentation
Size: 403701 bytes
Desc: rgk-issues-1.pptx
URL: <https://mailman.jlab.org/pipermail/clas12_rgk/attachments/20190410/ed55473c/attachment-0001.pptx>