User name riordan
Log entry time 14:23:21 on April 09, 2006
Entry number 170105
keyword=Neutron Arm Y Position and BigBite geometryI compared the the angles we get out from the kinematics module for
momentum transfer calculated from the tracking code to what we see in the
neutron arm for elastic events.
Figure 1 is the momentum transfer theta compared to a rough theta in the
neutron arm ( theta_p = atan(na_hit_y/12m)+25.5deg for abs(na_hit_x)<.3m
). These seem to agree very well. (Incidentally, the 25.5 degree
central angle was guessed without previous knowledge since I originally
though the neutron arm was at 29degrees because that's what is in
db_run.dat. I'll correct that shortly).
Figure 2 is the momentum transfer phi vs neutron arm phi. (phi_p =
atan(na_hit_x/12m)). These do not seem to agree very well. I believe
that this is due to what we reconstruct for the Lab-y component of the
electon momentum in the tracking code. I should be able to use this data
to refine how we reconstruct the direction of the momentum and produce a
more refined set of parameters for the tracking code.
I think this is probably the best method we have for refining the
geometry for all of our configurations at the moment, since it is readily
available from hydrogen data we have.
Figure 1
Figure 2
