[Lowq] Minutes of the eg6 meeting on August 31

[Hovanes Egiyan]

  Minutes of the August 31 meeting


       From Lowqwiki

Present: Bayram, Dave, Stepan, Hovanes

On the phone: Raphael, Raffaella, Will

Notes by Hovanes.


    Contents

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    * 1 Announcements
      <http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Minutes_of_the_August_31_meeting#Announcements>
    * 2 EC timing
      <http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Minutes_of_the_August_31_meeting#EC_timing>
    * 3 Solenoid
      <http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Minutes_of_the_August_31_meeting#Solenoid>
    * 4 Hodoscope
      <http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Minutes_of_the_August_31_meeting#Hodoscope>

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    Announcements

    * Hovanes will start working for Hall D this fall and will not be
      able to continue performing the dutie of the analysis coordinator.
      Stepan agreed to be the eg6 analysis coordinator.


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    EC timing

    * Bayram looked at 6 GeV cooked data and he came to concluion that
      they do not need more calibrations, at least for the next cooking
      pass.
    * There was a small issue with 1.2 GeV timing when he looked at run
      61441
      <http://clasweb.jlab.org/rungroups/lowq/wiki/images/9/93/EC_TIMING_61441.pdf>.
      There was ~100ps offset for EC time with respect to SC time
      although the start times from both EC and SC were at zero.
    * An attempt to calibrate EC timing with 1.2 GeV data itself was not
      successful because because there were no hits in large areas of EC
      because of the CLAS configuration for low energy runs.
    * It was decided to keep only two calibration points for EC timing.



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    Solenoid

    * Hovanes compared the 3 solenoid field maps
      <http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Solenoid_update_31Aug2010>:


       1. The DC tracking FPACK map
       2. Solenoid field map currently being used in *gem* package
       3. Field map sent by Eric

    * His conclusion is that there is a bug in the tracking code when
      reading the field map. It creates 0.5cm offset in Z and R-directions.
    * This needs to be checked by cooking data. It would be good to
      check e1dvcs data on proton with and without "fixing" the bug and
      see if there is improvement in the elastic event angle and vertex
      matching.
    * We need a map with known current at the power supply and clearly
      identified format (preferably FPACK file similar to what is being
      used in DC tracking now).

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    Hodoscope

    * Wiil studied the ADC spectra for pedestals and production runs
      <http://clasweb.jlab.org/rungroups/lowq/wiki/index.php/Aug31_hodo>.
    * The ADC spectrum for the eg6 pedestal runs is drastically
      different from what Mikhail Yurov had from previous CLAS periods.
    * It seems like the HV were off during the pedestal runs. Therefore
      this particular run is useless even for pedestals extractions.
    * Stepan suggested to look at the plot of energy (ADC) vs timing
      (TDC) and use cuts on these plane to select out-of-time hits to
      get the pedestal and the single photoelectron peak.
    * Dave performed studies to identify ?^0 in IC/SH
      <http://www.jlab.org/%7Ejenkins/eg6/31aug10/31aug10.html>.
    * Dave looked at the time difference between hits in IC and CLAS. He
      sees two peaks, and he interprets the peak at -2ns as the events
      with correct timing and places cut around it.
    * He also uses energy corrections provided by F.-X. and looks at 2-?
      pairs.
    * Looking at the occupancy of the hodoscope he also see the missing
      segment due to HV channel being off.
    * Dave also uses cuts on the energy versus time plots to select
      in-time events in hodoscope. When he does it he sees that ~8% of
      pions produce hits in the hodoscope, which is more or less
      consistent with what Mikhail Yurov found (~5%).

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