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Home » Software Tools » Marlin et al » DDG4 particle gun (make isotropic particle gun flat in cos(theta), rather than in theta?)
DDG4 particle gun [message #2381] Mon, 29 February 2016 22:19 Go to previous message
jeans
Messages: 22
Registered: November 2012
Hello,

The isotropic particle gun in DDG4 results in a distribution uniform in theta, while a truly isotropic distribution should be uniform in cos(theta). Flat-in-theta gives a too-large number of events in the forward region. If one is an FCAL expert, the current definition is of course favourable, but for more general studies, a truly isotropic distribution would be more convenient!

(This same behaviour was also present in the Mokka particle gun.)

Would it be possible to change the definition of isotropic (in DD4hep/DDG4/src/Geant4IsotropeGenerator.cpp ), or to add the option of using the "correct" definition?

Cheers,
Daniel.
 
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