MOLLER Pion Background Meeting Wednesday, November 2, 2016 3:00pm EST

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Previous Meeting: MOLLER_Pion_Background_Meeting_Wednesday,_October_26,_2016_3:00pm_EST

Meeting Information

BlueJeans Call Information


Phone Number: 1-888-240-2560

Meeting ID: 624029893


  • Scott: Implementation of lead wall and strawman pion detector.
    • Separate pion development branch
    • Initial detector prototype.
  • Jacob: Starting to work on pion simulations.
  • David: present detector concept:
    • Kurtis: Quick search on radiation hardness of Lucite - Radiation Effects pg. 167 (pg.192 pdf doc)
      • Lucite unaffected by radiation to 0.82 Mrads (total absorbed dose?)
      • 91% to 56% light reduction at 5.5 Mrads (total absorbed dose?)
  • Any new business?


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

Not Attending:

Scribe: Kurtis

  • Looking at W&M ELOG 72.
    • Paul: 50% of the pion get through? I thought they were low energy. David - Will not be an unbiased measurement of the incident pions. Will need to use Monte Carlo to de-tangle.
    • Can we produce an efficiency plot? Energy spectrum of the pions that make it through the lead.
    • Any detector system will have some energy range. David - Shower Max is very much pion blind. Going to be difficult to unfold this background.
    • KK: We have never really worried about the momentum/energy dependence on the asymmetry. Has it changed at this point? Paul - Not really sure at this point.
    • Might be worth while to confirm with a theorist if the asymmetry dramatically changes between 1 Gev and lets say 3 GeV pions. If so, this pion detector method wouldn't work for this application.
    • Make sure you take into account the radiation length of the shower max detector. David - Estimate the lead wall thickness to account for presence of Shower max, later the lead wall can be reduced by 7 X_0 as the Shower Max will be there.
    • Paul: What about the hyperon asymmetry? Currently not in the simulation.
    • Open and closed sectors for each pion detector will bin two different pions energies, will also have two different pion fractions.
    • David: Really want a MIP detector, the best would be Quartz, however it is to pricey. Plan to use Lucite, the poor man's substitute.
    • Concerns:
      • Backgrounds in lucite
      • Differential sensitivity across pion energy
    • No major reason for azimuthial dependence on the pion dilution.
    • Should be able to measure dilution in a single septant, for the open and closed sector in that given septant.
    • KK: Could use two sets of dilution measurement devices. David: GEMS the cost driver in the dilution apparatus.
    • Could attempt to check energy spectrum of the exiting pions with a calorimeter.
    • Looking at Wouter's diagram
      • David: Distances will change over time.
      • KK: This first image is great to pass on to Javier for engineering of super structure costing.
    • David: Also should include trigger scintillators, as learned by Qweak.
    • Paul: Are you basically tracking to the center of the lead donut.
    • KK: Tracking resolution depends on matching tracks before and after the lead.
    • David: Tracking beam current should be low, so that we don't have signal pile-up.
    • David: From a dilution costing perspective, planning to still with GEMS. Straw-chambers could be another option.
    • KK: With straw-chambers have to be careful of hadronic background. Floating protons, ...
    • David: What does it mean to measure the pion rate? Maybe a relative measurement, ratios before and after lead wall.
    • KK: You are responsible for the lead donut.
    • David: More cost effective to go with lead for wall/donut.
    • Cost driver is the GEMS right now. KK: If straw-chambers would work, then GEMS could be removed. Need to look at the cost of straw-chambers.
    • Paul: What is the approximate size of the rate? David: Guess around 10kHz per septant.
    • Next step is to look at the energy spectrum of the electrons that come out of the lead donut.
    • Paul: Do you really need the lead glass calorimeter? David: Probably won't be used in the main pion rate analysis. Can be used as a cross-check.
    • KK: Need to keep the 1:1 pion to electron ratio for keep the desired stat. reach.
    • David: Pion dilution will be open closed dependent do to the electron open closed dependence.
  • Single collaboration meeting talk for the pion detector concept.
  • KK: Should review pion treatment from prior science review along with exploring more of this hyperon work.
    • Should collect all of the previous science info for the end of the collaboration meeting.
  • How much distance in Z do we need? Javier will ask. David: Quick estimate 1.5 meters, KK: Try to push it down to 1 meter.
  • Are the other detectors (not the Moller ring) exposed to line of sight to the beam pipe? Need to continue to think about shielding.