[Halld-pid] Start Counter Meeting Minutes, April 21, 2016

[Mark Ito]

Please find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_April_21,_2016 
.
________________________


  GlueX Start Counter Meeting, April 21, 2016,     Minutes

Present:

  * *FIU*: Werner Boeglin
  * *JLab*: Mark Ito (chair), Simon Taylor
  * *NU*: Sean Dobbs


      Calibration Update


        Propagation Delay Parametrization

Sean Propagation Time Corrections identified an inconsistency 
<https://halldweb.jlab.org/talks/2016/start_counter_prop_time_corr.pdf> 
in how the propagation time delay was parametrized between data and 
Monte Carlo. The issue was fixed in Pull Request #338 
<https://github.com/JeffersonLab/sim-recon/pull/338>. From the pull 
request:

  * Make propagation time corrections be consistently defined in terms
    of path length through scintillator
  * Rewrite plugins to pull expensive calculations outside of locks
  * Other minor changes


        Charged-Track/Start-Counter Matching

Sean did a study showing the distribution of azimuthal angle within a 
single start counter sector versus z where the azimuthal angle is 
determined by the intersection of the track with the start counter and 
only track/start-counter matches are considered. Plots were made for 
each of the 30 sectors 
<https://halldweb.jlab.org/wiki/images/a/a1/Sc_match.pdf>.

There is feature in the nose sections where a bias is seen in some 
counters toward higher or lower azimuth, depending on the counter. The 
bias direction and amplitude seems to be a smooth function of sector 
number making geometry a likely candidate for the source of the effect. 
Without correction we may have to increase the tolerance for a match in 
the nose region.


      Pre-Amp Strain Relief

Although this work was done at the beginning of the run, the photos 
showing the strain relief system were never shown at this meeting. See 
the photos and accompanying email from the designer 
<https://halldweb.jlab.org/talks/2016/start_counter_strain_relief/> for 
details.


      mcsmear Parameters

We reviewed the parameters 
<https://halldweb.jlab.org/wiki/index.php/Mcsmear_updates#START_COUNTER> 
again. See the discussion from last time 
<https://halldweb.jlab.org/wiki/index.php/GlueX_Start_Counter_Meeting,_March_24,_2016#mcsmear_parameters>. 


In discussing the energy resolution, we noted that we not have a good 
measurement of the number of photons per MeV and the measured resolution 
in real data contains both the intrinsic energy loss fluctuations as 
well as the effect of photon statistics. In Monte Carlo, these effects 
are put in separately, and so must be disentangled in the data if data 
is to be a guide.


      NIM/TDR

Werner reported that Eric Pooser has started a TDR contribution for the 
start counter.

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  * This page was last modified on 21 April 2016, at 14:09.


-- 
marki at jlab.org, (757)269-5295

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