Acceptance Function for PREX using the Hall A spectrometers
with 5 degree Septum Magnet

Dec 5, 2011    Robert Michaels

Contents of this directory

foldedacc.dat -- (ASCII text file) --
             the acceptance function \epsilon(\theta)
             first column is scattering angle (degrees)
             second column is the relative probability to 
             reach the detector

compareAccPb.gif  -- plot of acceptance function and comparison
             to simulation.

prex_acceptL.gif -- a picture of the acceptance.  Horizontal and
             vertical angles in radians.  The smallest scattering
             angle is on the right.


Comments on the acceptance function.

     Results are averaged over two spectrometers and
     have been corrected for multiple scattering.

     Theoretical comparisons should use this function
     to integrate over the acceptance of our spectrometers.
 
     As an example, the average asymmetry is (latex format):  

$$  A  = \frac{ \int  sin(\theta) d\theta  A  \frac{d\sigma}{d\Omega}  \epsilon(\theta)}
               {\int sin(\theta) d\theta \frac{d\sigma}{d\Omega} \epsilon(\theta)}   $$

where $\frac{d\sigma}{d\Omega}$ is the cross section.

contact
Robert Michaels
Jefferson Lab
e-mail : rom@jlab.org