JEF meeting, April 7, 2017

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Meeting time and location= 11:00 EST (JLab time) CC-f228

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  1. Hybrid calorimeter simulation update


Attendees: Liping G., Shuang H., Dave M., Zisis P., Alex S., S.T.

  • Shuang showed π0γγ reconstructed events from the entire Spring 2017 data set for both the full energy range (Eγ>3) and for Eγ>6 GeV. In the η mass range the background due to the η→3π0 channel is greatly reduced for the higher energy cut, but there is still no evidence for a signal in the η→π0γγ channel. Her figures are on DocDb: [1]. She also looked at η→2γ channel for normalization so that we can estimate how many rare decay signals would show up in the 4γ plots -- this is a small number on the order of 20-30. She also looked at the acceptance for the 2γ channel: this was about 7%, which seems low but is partly explained by the fact that we do not have complete coverage in Eγ below the coherent peak. However, Dave mentioned that Teagan also sees potential issues in the 2γ channel.
  • Due to the likelihood of showers merging in the BCAL, the recommendation is to do the analysis for the rare channel in FCAL only. We may need to raise the threshold in the FCAL from 100 MeV to 200 MeV or higher.
  • We briefly discussed S.T.'s presentation to the GlueX physics working group. The main thing that came up was the logistics of unstacking and restacking the FCAL with the lead tungstate crystals. This could easily take a year; it would be a good thing if I.U. maintained some ownership of the FCAL even after the upgrade.
  • Hall-C plans to purchase lead tungstate crystals -- perhaps we could use them after they are done?
  • Sascha is working on background studies and plans to give an update next week.
  • S.T. continues to work on simulations for the Gluex phase-IV running conditions. The amount of leakage from the π0π0 channel even with a two-pion veto is a concern and the appropriate normalization of the events relative to the η channels needs work.
  • Things to do:
    • PYTHIA-based background estimations including channels in addition to 2π0
    • Completion of MC studies using realistic GlueX running conditions.
    • Plots from real data to use as backup.
    • Proposal draft.