[d2n-analysis-talk] H2 cross section

[posik at jlab.org]

Hi Brad,

 So I am looking into the BBNormAna stuff now. In the mean time last night
I went to look at how to get the other parameters that I will need to
compute the H2 cross section.

  The first thing that I want to comment on is the shape of L.tr.tg_th,
there looks to be a dip in the center of the distribution (the middle
plot in the fig attached). Is this normal?, Or could something maybe be
blocking the angle?

  With that said, then next thing I want to do is calculate the density of
our target. To do this I use the Ideal gas law and have

  D = (P*M)/(R*T) where P = pressure, M = molar mass of H2, R = gas
constant and T= temperature

  So looking at the end of run file I find:

  HacAi_hpchan7: Temp at Ref. Cell : 41.9336
  HacAi_hpchan8: Temp at Ref. Cell : 42.3438
  HacAi_hpchan9: Temp at Ref. Cell : 41.123
  Reference Cell Gas Pressure (psi) : -277.5
  Reference Cell System Vacuum (Torr) : -282

I am assuming that the temp is in Celsius? And I am not sure why the
pressure is negative. Is this a sort of gauge pressure meaning that it is
relative to some other pressure, ie atmosphere?

 The next thing that shows up in the cross-section is the acceptance of
the LHRS which consists of 3 parameters (d_ang,d_z and d_E). In all
papers that I have read they calculate these quantities using Monte Carlo
simulation.
I do not have a Monte Carlo set up to simulate the angular acceptance. I
spoke to Huan and he had told me that there is an acceptance problem with
his Monte-Carlo acceptance. But he had told me to I could make acceptance
cuts and just assume the angular acceptance is 1.

Thanks
Matt

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