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Re: box generator [message #4324 is a reply to message #4292] Thu, 24 May 2007 19:43 Go to previous message
Pablo Genova is currently offline  Pablo Genova
Messages: 32
Registered: May 2007
continuous participant
From: *PV.INFN.IT
Hi Stefano and generators' people,

triggered also by Katarzyna and Felice, I checked the two generators, the former CbmBoxGenerator and the PndBoxGenerator with option SetCosTheta(), which Stefano wrote recently.

As they suggested, I used a detector consisting of a sphere, everything in vacuum.

You can see the results in the attached plots

1. box_NON_uniform.jpg : with uniform theta.
2. box_uniform.jpg : with uniform cos theta.

As expected the first plot shows enhanced momenta in region x=0 & y=0, i. e. along the zed axis , and only using the SetCosTheta option you get the truly uniform generation.

So everything is OK, but I would strongly suggest to put a comment a like: "if you want to generate uniformly in the solid angle use the SetCosTheta() function" or even call that function
SetUniform3D() , to avoid errors or misunderstandings.

Maybe even in the macros it is better to default to uniform distributions, with suitable comment to clear this to the user.

(I went into the mistake of supposing uniform what uniform was not!)

ciao, Pablo

ps: this forum is wonderful!

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