[d2n-analysis-talk] low momentum pre-shower energy

[posik at jlab.org]

Hi all,

   Yesterday it was pointed out again that the pre-shower energy of Vahe's
simulation does not match the data at low momentum. Vahe's simulation
does not account for pions, so this may be a contributing factor.
Another potential contribution to the difference between the data and
simulated pre-shower energy, was the bad pre-shower block on the large
angle side of the detector that could lead to lower pre-shower energy.
In the figure labeled gap.png, you can clearly see the bad pre-shower
block. This block is located near the physical top of the detector.

 To see if this bad pre-shower block affects the pre-shower energy. To
match the simulation that Vahe did I first placed a cut on the momentum,
so my momentum range was 0.6 +/- 0.01 GeV. In the figure
Energy_600MeV.png:

I then placed  Cerenkov cuts that select the large and small angles of the
detector and plotted the pre-shower energy for each of the two angles. The
small angle pre-shower is in red and the large angle pre-shower energy is
in blue. In addition to this I also plotted the pre-shower in black and
shower energy in green with a total Cerenkov cut that selects both of the
angles (small angle || large angle) for comparison.

So looking at these energy distributions, it seems that the bad pre-shower
block does not change the energy distribution, it just suppresses the
counts. Although it is difficult to see how much the bad pre-shower block
suppresses the counts due to the rate difference between the large and
small angle sides.

-Matt
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