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The magnetic spin of the neutrino

The measurements of the neutrino magnetic spin have been made essentially at nuclear plants (Reines experiment in 1976 or the one of Krasnoiarsk in 1992), by observing the diffusion of neutrinos on electrons orbiting into atoms. No positive result has been obtained for now; only a superior limit of 5.8 10-20 MeV/Tesla for the nue. Limits on magnetic spin of numu and nutau are obtained directly from measurements made at particle accelerators or by astrophysical considerations.

Classical picture: The magnetic spin is a measurable quantity representing the spin or kinetic momentum of the particle. The kinetic momentum is linked to the "spin velocity" of the particle.

More pragmatic picture: The magnetic spin is a measurable quantity representing one of the electromagnetic components of the particle interactions. In the case of neutrino, the magnetic spin gives to it the possibility to interact electro-magnetically with electrons. If its magnetic spin is for instance 10-20 MeV/Tesla and if its energy is about 2 MeV, then its probability to interact electro-magnetically becomes of the same order of magnitude as its probability to interact by weak interaction.

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Last update: 26/06/1999 : http://wwwlapp.in2p3.fr/neutrinos/ammagnet.html
Didier Verkindt