Re: Spin tracking of moving muons

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On Thu, 19 Feb 2009 01:29:47 GMT, Gumplinger Peter wrote:

> Hi Kevin,
> 
> Thanks for your detailed and constructive forum posting.
>

And thanks for your detailed answers. I've now got everything I need to make forward progress.

> According to Jackson: "If the particle is relativistic (beta->1), even
> the presence of an electric field causes the longitudinal polarization
> to change only very slowly, at a rate proportional to gamma**(-2) times
> the electric field component perpendicular to v_vector." (I assume you
> are dealing with 'surface muons' - longitudinal polarized muons?)
>

Yes and no. I'm working with a student on a project with surface muons, with no E fields, but where stopped muon spin evolution is important. But I'm also working on a next generation g-2 experiment, with large quadrupole E fields that rotate spins, requiring a non-negligible correction to the final experimental results. And, I've just been asked to consider doing some spin tracking for a potential muon EDM experiment, with very large E fields. So, all these issues are very interesting to me.

I have been able to implement the missing terms in the G4EqEMFieldWithSpin class, and will send them to you and post them here once I've tested them. I also plan to implement the EDM field equations; although I doubt anyone else will have a use for them, I plan on offering the implementation for inclusion in the Geant4 distribution if you would be interested.