[Halld-cal] BCAL sampling simulation

[David Lawrence]

Hi Andrei,

   I promised at the meeting on Tuesday to send you an e-mail indicating 
the format of the the resolution tables that I would prefer. I'm CC-ing 
the calorimetry mailing list in case anyone else would like to comment.

First, let me verify what the input parameters are:

1. Total energy of incident photon that created the shower
2. Theta angle of the incident photon
3. Distance of incident photon at point of entry into BCAL from center 
of module in azimuthal direction
4. Energy deposited in cell (whole cell, not just fibers)
5. Cell row within module (1-10)
6. Cell column within module (1-4)

I assume that depth of shower is already taken into account by index 5 
and so is not needed as separate input parameter. Let me know if this is 
not correct.

Also, please remind me how the value for parameter 4. is used. Is this 
just a cut on Ecell<50MeV or Ecell>50MeV to decide which parameter set 
to use, or are there more than 2 bins in this parameter?

What you will provide:
   Effectively, a six dimensional table that has 2 values, A.) the 
sampling fraction and B.) the sampling fluctuation coefficient.

I would suggest providing these in the form of a ROOT file containing a 
set of 3-dimensional (TH3F) histograms.
  - indices x,y,z of those would correspond to input parameters 1,2,3 
listed above
  - The names of the histograms would contain indices 4,5,6.
     e.g.
               SampFrac_0_50MeV_row2_col4
               FluctuationCoeff_0_50MeV_row2_col4

If my understanding is correct, this will lead to:
  2*10*4 = 80 histograms for each of the 2 values or 160 histograms total

Each histogram would be 8*12*32 = 3072 bins

So for single precision, this would be about a 2MB file, not accounting 
for any compression.

Please let me know if anything is incorrect or you have another idea 
regarding format.

On a side note, I would like to confirm the 272keV threshold you used is 
correct. To make it clear, this is the threshold hdgeant uses to decided 
whether to write the hit for a single SiPM to the output file, or 
discard it. The 272keV comes from requiring 1MeV deposition on the far 
end which would attenuate to 272keV on the opposite end. Electronics 
thresholds are much higher, but applied later after additional effects 
(e.g. dark hits) are included.

Regards,
-David