[d2n-analysis-talk] LHRS H2 elastic theta structure

[posik at jlab.org]

Hi all,

So after today's meeting it was suggested that the dip in the theta
distribution of the LHRS of the H2 runs could be due to the whole in the
BB shower calorimeter Since the T5 is a coin trigger and the BB shower I
believe forms the BB trigger, if the BB has a trigger hole, then the T5
should inherit this hole.

 So to see if this is the case I plotted the LHRS "L.tr.tg_th" (th.png)
and the LHRS theta vs phi (th_ph_mod.png) (see plots below). You will
notice in the T5 trigger cuts (left plots) there is a dip in the theta
variable and in the theta vs. phi 2D plot there is a clear hole in the
acceptance. I also plotted the same variables with the T3 trigger (LHRS
trigger) the right plots. The dip in theta now goes away and in the 2D
theta vs phi the acceptance no longer has a hole.

So it seems as though this theta dip is due to the hole in the BB trigger
from the shower calorimeter.

Matt
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