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Forum: Fields: Magnetic and Otherwise
Re: None What are y and dydx in the equation of motion? (Bertalan Juhasz)
Re: None Re: What are y and dydx in the equation of motion? (John Apostolakis)
Date: 07 Apr, 2004
From: Bertalan Juhasz <Bertalan.Juhasz@cern.ch>

Thank you for the fast answer!

> My notes at hand are that the components of these vectors are:
> [y] 
> 0, 1, 2:  (x, y, z)     in Geant4 length units   (mm by default)
> 3, 4, 5:  (px, py, pz)  in Geant4 momentum units (GeV/c)
> 7:         time in lab frame
> Likely other components are not needed or important

Are the y(3,4,5) the momentum or momentum x speed_of_light? The code in G4EqMagElectricField.cc suggests it is the latter. Also, the derivative of the momentum with respect to the distance is not really a force.

> dyds are the derivatives of the above with respect to the distance 
> along the curve, (hence the name). The units (of ds) are length 
> in G4 units.

Regards,

Bertalan

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1 None: Re: What are y and dydx in the equation of motion?   (michel maire - 10 Apr, 2004)
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