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Question why polarization vector is not perpendicular to momentum ? 

Forum: Electromagnetic Processes
Date: Sep 29, 05:46
From: <zhangyf@ihep.ac.cn>

Hi,

Thanks Peter for your nice guiding firstly!

When I run the Pol01 (extented/polarisation/Pol01) program, the problem that has been showed in "Paticle" Category in this forum happens again.

Changes in the Pol01:

(1) the material of Box was changed to be G4_PLASTIC_SC_VINYLTOLUENE (2) boxSizeZ = 50. *mm (3) 122.1 keV gamma rays

Results:

>> gun/polarization 1 0 0
>> tracking/verbose 3
>> run/beamOn 1
...
      -----------------------------------------------------------------------
        StepPoint Information               PreStep            PostStep
      -----------------------------------------------------------------------
         Position - x (mm)   :                    0                   0
         Position - y (mm)   :                    0                   0
         Position - z (mm)   :                  -25    13.0631383823411
         Global Time (ns)    :  0.08339102379953801  0.2103559869486146
         Local Time (ns)     :  0.08339102379953801  0.2103559869486146
         Proper Time (ns)    :                    0                   0
         Momentum Direct - x :                    0 -0.1869627173785501
         Momentum Direct - y :                    0 -0.9193385470136727
         Momentum Direct - z :                    1  0.3462103093283293
         Momentum - x (MeV/c):                    0-0.01974379366979246
         Momentum - y (MeV/c):                    0-0.09708476021009742
         Momentum - z (MeV/c):               0.1221 0.03656079142181843
         Total Energy (MeV)  :               0.1221  0.1056028386120239
         Kinetic Energy (MeV):               0.1221  0.1056028386120239
         Velocity (mm/ns)    :           299.792458          299.792458
         Volume Name         : G4_PLASTIC_SC_VINYLTOLUENEG4_PLASTIC_SC_VINYLTOLU ENE
         Safety (mm)         :                    0    11.9368616176589
         Polarization - x    :                    1 -0.9794236864290253
         Polarization - y    :                    0 -0.1386048373629611
         Polarization - Z    :                    0                   0
         Weight              :                    1                   1
         Step Status         :           Geom Limit       PostStep Proc
         Process defined Step:       Transportation           pol-compt
      -----------------------------------------------------------------------

Questions:

According to those results (assumed to be calculated in the world frame), in the poststep, the angle between momentum and polar vector of gamma ray is about 72 degree. Why did they not perpendicular to each other? What's wrong?

Thanks for your help!

Best Regards! zhangyf

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1 None: Re: why polarization vector is not perpendicular to momentum ?   (Andreas Schaelicke - Sep 30, 13:35)
(_ Ok: Re: why polarization vector is not perpendicular to momentum ?   (zhangyf@ihep.ac.cn - Oct 08, 08:38)
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