[Clas_cascades] Minutes of eg3 meeting on Aug 13

[Hovanes Egiyan]

  Minutes of Aug 13 2009


       From EG3Wiki

Present: Hovanes, Kijun

On the phone: Ralph, Zhiwen, Lewis, Haiyun

Notes by Hovanes.


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    Normalization studies

    Lewis started the meeting by a report on the status of the
    normalization studies.

        * He showed us the y-projections of the plots for the normlaized
          yields versus the run number for trigger bit 5 and trigger bit
          6 separately.
        * Hovanes suggested that these plots show that there is trigger
          inefficiency for trigger bit 6 even even for when the start
          counter is not put in coincidence with MOR since the average
          rates before Christmas for trigger bit 6 are lower. In
          Hovanes' plots this was not present, probably because Hovanes
          was looking at non-exclusive events.
        * Kijun pointed out that there are points present in the
          y-projection plots, which are clearly absent from the
          run-dependent histograms. Lewis said that he still needs to
          take these points out from the y-projection histograms, they
          were not generated directly from the 2D histograms shown on
          the same page.

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    Tagger timing studies

    Haiyun showed his findings on the timing of the tagger T-counters. 

        * The plots of the photon times in the tagger T-counters #9 and
          #11 have peaks at negative times. Haiyun suspects that this
          may be the cause of the double peaking he saw previously, and
          might be a source of inefficiency.
        * The counter number there is the number of the physical
          counter, not the logical number in the software. Haiyun
          interpreted the two sequential numbers in TAGR->T_id as left
          and right PMTs of the same physical counter. Hovanes suggested
          that it is very unlikely to be correct. Instead, the two
          sequential numbers are just two different geometrical parts of
          the same physical counter.
        * Hovanes also pointed out that the negative times in the
          quantity plotted, which is the time of the photon at the
          center of the target with respect to the time the event
          trigger happened, does not necessarily mean that there will be
          double peaking in the time difference between the tagger time
          and start time determined from the TOF. The TAGR-TOF time
          difference is the quantity the cuts in physics analysis are
          applied to select desired events. But it was unclear to the
          participants why there would be a "trigger time" jitter
          depending on which part of the tagger T-counter the hit
          occurred and which other T-counter there was an overlap with.
        * Haiyun will continue to investigate this issue.

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