MOLLER Pion Background Meeting Wednesday, October 5, 2016 3:00pm EST

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Previous Meeting: MOLLER_Pion_Background_Meeting_Thursday,_September_22,_2016_3:00pm_EST

Meeting Information

BlueJeans Call Information


Phone Number: 1-800-240-2560

Meeting ID: 624029893


  • Scott: Implementation of lead wall and strawman pion detector.
  • Jacob: Starting to work on pion simulations.
  • Initial plan: Implement single septant pion detector behind lead wall.
    • To be placed behind Moller ring to begin with.
    • Lead tungstate(PbWO_4) blocks.
    • Wouter's initial concept of the pion detector geometry. (See previous meeting page for details)
  • Any new business?


Attendees: Mark P., Rakitha, Kurtis, KK, David, Seamus, Jacob, Scott

Not Attending:

Scribe: Kurtis

  • See Mark P. recent email for some notes on a discussion he had with KK. Will discuss more in the future.
  • Scott currently working moving his lead wall and pion detector into it's own separate gdml file. Figured this would be best for future development.
  • Jacob just starting on getting up to speed on the remoll simulation. Will take Scott's pion straw/wall detector and due simulations at 400 and 500 mm lead wall thickness. Planning to investigate the length of the prototype detector module, for cost estimate.
  • David: Jim Dowd, working on Qweak, has a preliminary transverse pion asymmetry that is on the order of 10-20 ppm. Meaning it could be larger than the pion PV asymmetry by a factor of 2 to 10.
  • KK: Need a systematic correction for the pion background also needs to bound the hyperion contribution.
  • KK: Shower max and electron suppression should be talked about in terms of radiations lengths. At the 10^-4 level.
  • Looking at
  • What should the P/E ratio should be? Take a look at the notes from Mark P.(see email):
    • What is the optimum way to extract N_pi/N_ee from remoll.
    • KK: Suggests that we need a defined method for extracting these values.
    • David's concern, particle ID detectors can be difficult to determine the dilutions.
    • Thinking we need to know N_pi/N_ee ratio at the 10% level (for the dilution).
    • 0.2 ppb uncertainty is the goal for the pion correction to A_ee
    • Dilution could be measured with coincidence with MIP in the shower max with pion detector. See third bullet point from the notes.
    • Simulations should be done with the shower-max/temp. stand in to check MIP coincidence.
    • Single GEM plane could be used with rotator for pointing measurement to shower-max.
    • KK: Doesn't think there is any crazy reason why the pion distribution should change wildly with phi.
    • David: Just putting a pion detector for Moller ring, then order of magnitude correction for other rings could be down with simulation for a given normalization taken from measurement in the Moller ring and pion detector.
    • David: Will have to revisit the Yuxiang's pion correction for the simultatous ring extraction, in the future.
    • Paul: Interested in the energy spectrum of the pions going through the main detector rings. KK recalls energy between 1-2 GeV.
    • KK: This should be confirmed in the future.
    • Paul: What is the dE/dx for these low energy pions (lower than SLAC's pions)? Can be answered soon.
    • David: We should be able to produce these plots soon. Definitely different lower energy spectrum than what SLAC saw.
    • David: How worried(Paul) are you about pion transverse asymmetries? Paul: Worried about it, thought about it a bit.
    • Paul: Could probably get away with a minimum of three detectors. KK: Full coverage would be better. David: Should segment behind open/closed/transition sector for a given septant as a base line.
  • KK: Two step process - Make intial guess with best available numbers. Then do the full study.
  • David: Lead glass for PbWO_4, estimate the cost for each? Radiation problems with lead glass, maybe anealing might work in this application.
  • Radiation worry for the lead glass could come from the background in the hall.
  • Paul: HAPPEX style shower detector might work.(Lead lucite) David: Depends on how much calorimetery we would need?
  • HAPPEX 2 used quartz detectors.
  • KK: Could sacrifice the stat. width with a low cost design that reduces energy resolution.
  • We are looking for one to one for the light response.
  • Measure the integrating asymmetry everywhere, only need to counting measurement in a few septants.