[d2n-analysis-talk] BB H2 elastic momentum

[posik at jlab.org]

Hi Brad,

  In our last meeting after looking at the sh/ps Energy vs the ps energy,
there were a lot of events that looked like pion type events (low
preshower energy events). I attached the image from last meeting below
(pid.png). Just as a refresher, the left is with the proton cuts (as
defined by the LHRS and T5 coin trigger) and BB vz target and one track
cuts. The Right has the same cuts as the left and also a 30 chan BB
cerenkov ADC cut and a BB cerenkov TDC cut.

  Brad has suggested looking at what the reconstructed momentum looks
like. Here is a plot of the BigBite reconstructed momentum from our
1pass H2 run. I attached the plot below. The left plot is with T2
trigger cut and the right plot is with a coin T5 trigger cut. Both plots
also have a BB one track cut. The mean for the T5 trigger cut momentum
falls at ~0.862 GeV, which about what is expected. If I use the elastic
scattering formula

 p' = p/{(1+[2*(p/M)*sin^2(th)]},

where p is the momentum (assume electron mass 0, p = 1.2 Gev)
p' is the scattered momentum
M is the proton mass 0.938 GeV
th is half of the scattering angle (22.5 degrees)

I get p' = 0.873 GeV

-matt
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