Progress Report on work on non-linear response of FMS

Summary of progress:
  1.   Based on pion peak position as a function of the two photon energies, a best approximation for the correction is reported with a 5th order polynomial in energy for the photon energy correction.
  2. The fit works fairly well for pions, in most kinematic regions better than 5%.
  3. There is evidence of underestimated correction at below 10GeV and over correction at about 20GeV.
  4. Small Cell North and South are very similar.
  5. From Eta analysis, when 1 photon has energy of about 7 GeV, the Eta mass is quite low and the corrections implied by the model are low by about 10%. When 1 photon has energy of about 12 GeV,  the corrections are about right. When 1 photon has energy of about 16 GeV, the corrections are too high by about 5%.
  6. Although the correction of was designed for small cells, we applying the same corrections to events with 1 photon in small cells and one in large cells, the Eta’s are observed to require corrections that are smaller by about 10% than those proposed. It does not matter very much if the more energetic photon is in the small cells or large cells.
  7. We show a pion peak analysis with two photons in the large cell FMS.  Analysis of 1 low energy (7 GeV) and variation in energy of the higher energy photon, suggest that for North Large Cells we need a very  different correction function. North Large corrections for soft photons my be as much as 20% less that that of the small cell and the slope may be slightly positive.
  8. We next need to investigate the difference between reconstruction algorithms used for well separated photons and overlapping photons.
  9. Unlike Small Cells, the North and South corrections will apparently be very different for large cells.

For details and plots, see attached pdf.