03/31/2020

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Present: M.D., A.D., S.Š, J.S.

  • General:
  • SŠ: Coded the unpolarized and polarized Bethe-Heitler formulae, see his report
    • AD's comments on Simon's document:
      • BH asymmetries seem very small. For GDH, we are looking at asymmetries at the 3% level (see e.g. Helbing review's Fig. 38: Δσ 10 μb, with A=Δσ/(2σ₀). It seems the BH asymmetry is lower by significantly more an order of magnitude. Further, Mark simulation indicate a 10% trigger efficiency for BH, so if it is true, Δσ is further suppressed by an order of magnitude.

This points toward the possibility that we can ignore the BH for the proposal.

      • Regarding the structure functions for the asymmetry, the atomic form factors should not be needed since the atoms are not polarized.
      • For g1 and g2, probably only their values at very small-x that are truly relevant. If so, one can use a simple Regge parameterization of g1, see e.g. arXiv:1808.03202. For g2, we could just assume g2ww(x,Q²)=-g1(x,Q²)+ ∫x¹g₁(y,Q²)/y dy.
***For question #2, the angle coverage, we are planing to use the Compton Calorimeter, which cover down to 0.2°. (Note: we do not have the ComCal in the simulation yet).