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Question Problems with GPS and position and direction distributions? 

Keywords: GPS, position and direction distributions, biasing, usr-defined histograms
Forum: Particles
Date: 17 Oct, 2007
From: Shahrokh <Shahrokh>

Hi,
 
I have some questions about to define position and angular distributions by using GPS, as follows:

When I execute my application, the particles traverse a plane. For each particle traversing 
this plane the position (X and Y coordinates), direction ( X, Y and Z components of momentum direction ) 
and energy are stored in six 1-D histograms by using AIDA that these horizontal axes are 
the position coordinates, the components of momentum direction and energy, respectively in which 
the particle incident upon the plane. Afterwards, I want to define these distributions (positions, directions 
and energy) by using GPS commands in user-defined histograms or biasing and save these commands in a macro file 
and then I execute again from this planar source by having these distributions in this macro file. 
In the following, I divide my works in three steps, the definition of energy, position and angular distributions 
from these six 1-D histograms by using GPS commands:
 
---------------------------
1- Energy distribution:
I can initialize this energy distribution (1-D histogram) by using the commands following:
/gps/ene/type User
/gps/hist/type energy
/gps/hist/point ... ...
 
/gps/hist/point is followed by its two arguments - the upper boundary of the bin and weight of the bin. 
I think I do it correctly. In your opinion, is it correct?
 
---------------------------
2- Direction distribution:
For the initialization of the direction distribution by using GPS, firstly I must get 
angular distribution (Phi and Theta) from momentum direction distribution. 
For this purpose, after getting X, Y and Z components of momentum direction, I can calculate 
Phi and Theta angles with the following formulas:
 
Phi = Arctan(Py/Px)
Theta = Pi - Arccos(Pz)
 
After getting two 1-D histograms from Phi and Theta distributions, I can use the following commands:
For Theta:
/gps/ang/type user
/gps/hist/type theta
/gps/hist/point ... ...
...
For Phi:
/gps/ang/type user
/gps/hist/type phi
/gps/hist/point ... ...
...
I think I do it correctly. In your opinion, is it correct?
---------------------------
3- Position distribution:
The position distribution in this plane is that many particles emanate from a region in the rectangular shape 
and a few particles emanate from the out of this region.
 
At now, I want to define a planar source by using this position distribution, but I do not know how to do it. 
I thought that I could do it by using the commands as follows:
/gps/pos/type user
/gps/hist/type biasx
/gps/hist/point ... ...
...
 
Unfortunately, I did not see the command as similar to /gps/pos/type user. 
Although I do not exactly understand the concept of biasing.
How can I do it?
Please tell me the role of biasing.
 
In the other hands, is it correct that I bias distributions by using two 1-D histograms of X and Y components, synchronously? 
Does it superimpose into the rectangular region?
 
Please guide me, 
 
Shahrokh.

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1 Question: Re: Problems with GPS and position and direction distributions?   (Shahrokh - 20 Oct, 2007)
3 None: Re: Problems with GPS and position and direction distributions?   (Fan Lei - 02 Nov, 2007)
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