[G12] resolution of tagger in kinematic fitter

[Carlos Salgado]

Hi

Follow the discussion in last g12 meeting.

The formula in the code for the variance of the photon bean energy is OK.

The uncertainty in the energy of the photon is 0.001* E_beam (per NIM and Eugene P.) The hodos were built such that this is true (different widths)

Then consider a counter of width (energy) "a"  where the (assume) energy distribution is flat: then Variance = sigma^2 = 1/a* int^a_0 E^2 dE = a^2/3

Therefore if we distribute the uncertainty over a counter (energy bin) the variance is : sigma^2 = (0.001*E_beam)**2/3

=Carlos