[Primex] preparations for the PrimEx-II run

[Ashot Gasparian]

     Dear PrimEx-II Collaborators,

  The chances are increasing that the PrimEx-II experiment
  may run earlier than it is currently listed in the schedule.
  There is a high probability that we may run in the fall of
  this year or in the beginning of the next year. The final
  decision, looks like, will be made sometime in April/May.

  In all cases we have extremely short time to prepare the
  experiment itself and the experimental setup to reach the
  long promised 1.4% precision. This task is getting more
  difficult when we look at the availability of Hall B to
  work on our setup. There are ONLY to time periods for this
  work, one is already ongoing and it will end in March 10
  with the closing of Hall B. The next opening is scheduled
  from the middle of July to sometime in August 20.

  Besides the inspection and preparation of the previous
  experimental setup to make it physically ready for the new
  run, we have to come up with critical improvements in the
  setup to reach the promised (in PAC33) more statistics
  (with the approved less beam time) and control of all
  backgrounds in the data set to possibly reach the stable
  and controllable extraction of the decay width on a
  percent level.

  Summarizing many discussions on this subject, done in the
  past, here is the itemized list of work for those possible
  improvements:

  1)The statistics: the only effective way to improve the
    statistics is to revisit the DAQ system and increase
    the event rate for more than a factor of 5 ( ~ 5KHz).
    This was discussed in the PAC33.
    Some initial activities are already started on this part.
    Any suggestions or comments are more than welcomed.

  2)Redaction of the backgrounds: up to now we came up with
    a 3 major ways to significantly decrease the backgrounds
    in the experiment:

    a)e+e- background possibly coming from the collimators
      and deflected by the permanent magnet. This background
      is reflected in the Compton data, therefore it is not
      a direct contribution for the pi0 data set. However,
      given to the importance of the Compton, we need to fix
      it. Some very initial work already started to try to
      increase the Bdl of the permanent magnet.
      Any help and idea are more than welcomed.
    b)The veto counters are critical for the charged background
      redaction. It was initially designed on that way and we
      also saw their importance in the background redaction
      process in data analysis.
      We need to inspect the veto counters. If it is necessary
      we need to redo them to provide a robust set of "veto
      efficiencies" with their well known errors for the entire
      HyCal calorimeter.
      This process needs to start now.

    c)Timing information from HyCal channels: We hope that if
      we instrument each channel (or in wars case, each summing
      group) of the HyCal with a TDC, that will significantly
      help to reduce the accidental background in the experiment.
      This needs more work and electronics. But, given to its
      importance, we need to try everything possible to do that.
      Initial work is already started, TDCs are potentially
      located, but we need to come up with the discriminators
      and cabling. Any help on this part is more than welcomed.

  For sure, items listed above are subject for more discussions
  and improvements. Given to the short time left for the
  preparation we need to effectively combine email discussions
  with the Friday meetings.

  We are critically short with onsite manpower to work on the
  setup. We need more onsite manpower (professors, postdocs,
  students) now, for the summer period and during the run.
  Please come up with your contributions on this important
  part of the collaborative work for the successful preparation
  of the PrimEx-II setup and the run.

  Best regards,
  Ashot



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Ashot Gasparian                    Phone:(336)285-2112 (NC A&T)
Professor of Physics
Physics Department                       (757)-269-7914 JLab
NC A&T State University              Fax:(757)-269-6273 JLab
Greensboro, NC 27411               email: gasparan at jlab.org
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