FDC geometry options

[David Lawrence <davidl@jlab.org>]

Hi Folks,

    I want to follow up on an issue from the June 5th Software meeting 
regarding material in the detector for the various FDC options. At that 
meeting, Mihajlo showed a couple of plots comparing the single photon 
reconstruction efficiencies for the "original" FDC design as well as 
options 1 and 2. His plots can be seen here:

http://www.jlab.org/Hall-D/software/wiki/index.php/Single_photon_reconstruction_efficiency

His plots showed realtively little difference between the various 
geometries with only statistical differences between the option1 and 
option  2 geometries. This was inconsistent with the momentum resolution 
plots I showed on the same day which indicated there was a discernible 
difference between the geometries.

Since then, I have produced radiation length scans of the 3 geometries 
which can be seen on the wiki here:

http://www.jlab.org/Hall-D/software/wiki/index.php/Image:20070615_radlen_root.gif

These appear to be consistent with scans done by Richard Jones that can 
be seen on the wiki here:

http://www.jlab.org/Hall-D/software/wiki/index.php/Detector_Material_Budget_in_the_Forward_Direction


In order to close the loop on this issue, I think we need to try and 
verify Mihajlo's plots. I suspect  there may have been a bug somewhere 
in the ones shown on June 5th. Mihajlo, could you please re-check this 
to see if you still seen the same thing?

-David

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