[Halld-cal] updated study of Fcal response in MC

[Richard Jones]

Hello Liping and all,

At your suggestion, I went back and redid my study of reconstructed showers
in the FCAL from MC, comparing hdgeant and hdgeant4, this time covering a
larger energy range up to 8 GeV. For the results, see the latest document
uploaded to docdb.

https://halldweb.jlab.org/doc-private/DocDB/ShowDocument?docid=3852

Here is a summary of what I found.

   1. I found a small bug in my fitting code that shifted the
   Ereconstructed down by 16 MeV relative to the generated in my earlier
   studies. This made the negative y-intercept in the Ereconstructed vs
   Egenerated appear worse than it actually is.
   2. I adjusted the output from shower particles in hdgeant4 relative to
   hdgeant down by 0.8% as we discussed a the last calorimeter meeting. This
   change is visible in the new results. I now claim that the agreement in the
   shower energy response between hdgeant and hdgeant4 is very good.
   3. With the new larger simulated energy range, my statistics of 100K
   events total is limiting my statistical accuracy in studying the
   non-linearity. Since there is no visible variation with polar angle seen in
   these individual plots, I added at the end a plot with the full statistics
   over the range 3-11 degrees, which has less statistical scatter and reveals
   the nonlinear behavior better.
   4. Above 4 GeV there is a very large rise in the reconstructed energy.
   Overall the nonlinear correction needs work at both the low and high energy
   ends of the Fcal spectrum.

-Richard Jones
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