[G12] Photon energy reconstruction issue in MC

[Andrea Celentano]

Hi MK,
last meeting before holidays I presented the corrections necessary for photons, for both MC and data. For MC, the reconstructed photon energy is affected by a major shift with respect to the generated one - much larger than what happens for real data. I remember you pointed out that this may be due to a non correct parametrization of the EC sampling fraction in the MC chain (gsim + gpp + a1c). For data, this effect is not present, since the difference between the measured photon energy and the “real” one (as obtained from the kin. fit of gamma p -> p pi0 -> p e+ e- (gamma)) is much smaller.
Therefore, I suspect this effect is related to an error in gsim or gpp rather than a1c, or that different reconstruction routines are used in a1c for data and MC.

Can you comment more on this?

Thanks
Bests,
Andrea