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Bradley,<br>
<br>
Great work. Is this cut unique for Mollers or similar thing may be
in the trident generator.<br>
<br>
Stepan<br>
<br>
<div class="moz-cite-prefix">On 5/13/16 3:25 AM, Bradley T Yale
wrote:<br>
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<p>I think I found the real problem with how the Moller
generator was initially set up.<br>
</p>
<p>This one affects the generated distribution a LOT more than
the RNG precision probably did, and explains the remaining
strangeness in the generated distribution.<br>
</p>
<p><br>
</p>
<p>Looking at the egs5 Moller procedure, the angular cut was
defined as:<br>
</p>
<p><br>
</p>
<p>abs(v(np)) > 0.010 radians <br>
</p>
<p><br>
</p>
<p>where v(np) is supposed to be theta.</p>
<p>However, the variables u, v, and w in egs are actually <b>directional
cosines</b>, p_x = p*u, p_y = p*v, and p_z = p*w.<br>
</p>
<p><br>
</p>
<p>So this means that in reality, the generator was saving
Moller events such that</p>
<p>abs [ sin(theta)*sin(phi) ] > 0.010<br>
</p>
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<p><br>
</p>
<p>which has a periodic nature to it. Plot this equation for
some value of phi (or just think about it) and you'll see
what was likely making these strange hills and gaps in the
energy distribution - full-wave rectified Mollers!</p>
<br>
The scattered beam simulation does correctly define theta
though:<br>
sqrt[ u^2 + v^2 ]<br>
<br>
I made a moller_v3 procedure with this correction (still
with a >10 mrad cut), and the comparison between before
and after is shown.<br>
The generated events now agree with the calculated cross
section (XS curve is shown on the 'bad' plot), and no
apparent missing events.<br>
<br>
These will be run through recon to see if we can finally get
good Moller agreement with data.<br>
I'm also going to try changing the scattered beam energy cut
shown in the software meeting to see if it fixes Tim's phi
vs. energy discrepancy.<br>
-Brad<br>
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