Re: new simulations for fdc

["Kornicer, Mihajlo" <mikornic@indiana.edu>]

Dear Elke,

here are some of the answers to your questions:
Single photons were generated from the center of the target
uniformly in polar angle and azimuth seen by the FCAL (0 < theta < 12 deg).
The grid for photon energies was from 50 MeV to 5 GeV in 100 MeV steps.

Plots of single photon reconstructio nefficiency that I put at

http://dustbunny.physics.indiana.edu/~mikornic/GlueX/fcal/NewFDCdesign/

are for photons that did not convert before the FCAL and produced a 
single cluster. Translated to cuts: one cluster reconstructed and one 
TrueShower registered in the FCAL. In terms of conversion probability, 
they are not exactly the inverse of the function shown in Fig. 9 of 
CD2-software document, GlueX-doc-806-v7.

Thus:
> did you simulate for a point like target or for an extended one
that was a particle gun with the vertex at (0, 0, 65) cm.

> did you place a cut that the conversion of the photon did really happen in
> the z-range of the FDC
There are no cuts other than on multiplicity of particles in the FCAL.
I do not have information regarding the point of conversion.
I can estimate whether a conversion has taken place before the FCAL 
only from particles that end-up in the FCAL.

>
> has the material of the cdc end-plate also been changed
I assume so, but I am not competent to answer.

>
> 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.
No

> Suggestions:
>
> would it be possible to have a 2 dimensional plot showing photons
> converting vs z and r (=radial distance from the beamline)
as I said, this requires special MC simulation to track all the particles
from their origin in the detector.

>
> it would be helpful to have this plots for fixed position along the
> beamline.
I can move the vertex along the z-axis and see if there is an effect.

I will be glad to answer any other question you might have if I can.

Regards,
Mihajlo

Quoting 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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