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Desciprtion of Monte Carlo signal simulation process.
1) We start with the energy deposited in the tile.
E_dep(MeV) from GEANT.
This includes Z^2 and pathlength effects, but does not include effects of light yeild
2) Convert from E_dep to photo-electrons(pe):
pe_nom(pe) = E_dep(MeV) * pe_per_MeV(pe/MeV)
To get pe_per_MeV we for tiles we need 3 pieces of information:
2a) pe_per_MeV for tiles comes from:
1.9 (MeV/meq) # mev_per_mip = 1.9 (tiles)
pe_per_mip(pe/meq) # calibration by PMT
saturation factor S(Z) for heavy ions # voltz: S(Z) = 0.608 + 0.393 exp(-0.00483 * Z^2)
attenuation factor from geometry A
(x) # only applied close to tile edge
2b) pe_per_MeV for ribbons comes from:
0.45 (MeV/meq) # mev_per_mip = 0.45 (ribbons)
pe_per_mip(pe/meq) # calibration by PMT
saturation factor S(Z) for heavy ions # voltz: S(Z) = 0.608 + 0.393 exp(-0.00483 * Z^2)
attenuation factor from geometry A (x) # applied as a function of length along ribbon/ segement
Combine these data to get pe_per_MeV for the hit in question
2c) pe_per_MeV(pe/MeV) = A (x) * S(Z) * pe_per_mip / mev_per_mip
Calculate the nominal # of photo-electorns
2d) pe_nom(pe) = E_dep(MeV) * pe_per_MeV(pe/MeV)
3) Throw Poissons to simulate dynode chain
pe_obs(pe) = PoissonAndGain(pe_nom,gain=4,iter=5)
This means we those a Poisson about pe_nom, then scale that number by the gain=4,
and throw a Poisson about new number, repeat iter=5 times.
4) Convert the signal into MIP equivalent
signal(meq) = pe_obs(pe) / pe_per_mip(pe/meq)
Where pe_per_mip(pe/meq) is the same number as used in step 2a or 2b above.
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