pair production

From: Maruyama, Takashi <tvm_at_SLAC.Stanford.EDU>
Date: Mon, 8 Jul 2013 16:17:07 -0700

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We have large angle pair production data from 5.5 GeV brems photons, where =
pairs are detected at more than 20 mrad, and we are comparing data and simu=
lation. In pair production, four variables, typically Energy(e+), Theta(e+)=
, Theta(e-), and Phi, are necessary to specify the final state. Since it is=
  not trivial to sample from a four-variable function and
photoproduction ta=
kes place at a very small angle, various approximations are used. Both EGS5=
  and Geant4 assume Phi=3D180 deg. Geant4 assumes Theta(e+)=3DTheta(e-),
le EGS5 treats Theta(e+) and Theta(e-) independently. Both EGS5 and Geant4 =
assume no correlation between Energy and angle. The double rate, where both=
  e+ and e- are scattered more than 20 mrad, is very sensitive to the
imation used in simulation. Fluka seems to yield best agreement with data. =
I am looking for the function that Fluka uses to simulate pair production, =
and any approximations used. I cannot find Physics Reference Manual in Flu=
ka web site.

   Takashi Maruyama
Received on Tue Jul 09 2013 - 09:29:56 CEST

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