new simulations for fdc

[Elke-Caroline Aschenauer <elke@jlab.org>]

Dear Mihajlo,

I have seen by accident some new plots from you studying the impact of the
fdc material on the photon reconstruction in the fcal.

First of al thanks a lot for doing these studies. I apologize in advance
if I ask questions which other people have already asked or you have
explained in your accompanying email, but I have only seen the plots.

I was pretty surprised that the overall improvement is not bigger, to
understand this better I have some suggestions what to plot and some
questions.

Questions:

did you simulate for a point like target or for an extended one

what was the photon energy you simulated

did you place a cut that the conversion of the photon did really happen in
the z-range of the FDC

has the material of the cdc end-plate also been changed

do you understand this sharp edge in the photon reconstruction
efficiency around 5 degree

do you have any idea why reducing the radiation length piratically
everywhere by a factor of 2 has so little influence.

Suggestions:

would it be possible to have a 2 dimensional plot showing photons
converting vs z and r (=radial distance from the beamline)

it would be helpful to have this plots for fixed position along the
beamline.

I apologize for so many questions, but the plots are really important and
on the first look not so easy to understand.

Have a nice evening
elke






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