|Message: Problems with transportation with spin||Not Logged In (login)|
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I am trying to track electrons and muons with spin in Geant4 9.5. I followed the prescription in the application developer's guide section 4.3.3. When muons go around in circles in a uniform B field, their polarization vector does indeed precess (initial polarization=[0,0,1] when headed in the +z direction).
But there are several problems:
1. The G4Track global time is not updated. This is surely a bug. When I use G4EqMagElectricField the track time is updated normally (but of course the track's polarization is zeroed).
2. The magnetic moment anomaly is set in G4Mag_SpinEqRhs, not in G4ParticleDefinition. This is a peculiar design decision which puts a rather complicated burden on developers (maintain a table of the anomalous magnetic moments for all particles, and set it in PreUserTrackingAction()).
3. The constructor of G4Mag_SpinEqRhs takes a G4MagneticField, not a G4ElectroMagneticField. As a result, the particles do not see any electric field -- neither spin nor momentum are changed by an E field.
4. According to the application developer's guide for 9.5, G4Transportation now has EnableUseMagneticMoment(). Calling this function does not seem to work: for a 2 MeV/c mu+ traveling along +z, with spin along +y, and in a 1000 tesla/meter B field gradient along +y (By=y in units tesla and mm), the track is not deflected.
I can live with item 2, but I need to get the others fixed. Suggestions?
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