BLTWG Meeting 4/10/2017

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  • Time: 11:30 EDT
  • Connecting: detailed instructions are here
  • Conference id: 536076821
  • Present: Richard J., Curtis M., Dan S., Alex B., Brendan P., Michael D., Justin S., Nathan S., Elton S., Alexandre D., Eugene C., Tim W., and Sascha S.


  1. Announcements
  2. Collaboration Meeting May 15-17, 2017 at Jefferson Lab.
  3. Progress with beam energy monitoring for spring 2017 run - Alexandre D.
  4. Radiative corrections to the triplet asymmetry - discussion
  5. CB spectrum and polarization calculation - Richard J.
  6. Update on flux measurements
  7. Update on calibrations
    1. TAGM timing resolution and efficiency update - Alex B.
    2. File:Plots.pdf Baalouch M.
  8. Update on simulations
  9. Any other business


Response from A. Afanasev to question about the size of radiative corrections in the triplet process:

I agree that 1.5% is getting close! For exclusive pion electroproduction (with a 3-body final state) we may have 25% overall correction factor, out of which 5% comes from a term proportional to cos(phi), i.e, azimuthally asymmetric; and 1% from cos(2phi). For Compton scattering - and your triplet process contains Compton amplitude - Thirring's low-energy theorem states that rad corrections to the cross section disappear in all orders of QED. We should see if sqrt(s) is small enough here to claim validity of the theorem. Chudakov, Ilyichev and myself calculated RC to Hall A Moller, and Konchatnyi&Korchin did RC for Ashot (Primex) for Compton scattering. I will check with Ashot on the outcome, but 1% was an accuracy goal for Primex.