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Bounds on the tau and muon neutrino vector and axial vector charge radius

Martin Hirsch·Enrico Nardi·Diego Restrepo
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Abstract

A Majorana neutrino is characterized by just one flavor diagonal electromagnetic form factor: the anapole moment, that in the static limit corresponds to the axial vector charge radius . Experimental information on this quantity is scarce, especially in the case of the tau neutrino. We present a comprehensive analysis of the available data on the single photon production process $e^+ e^- -> ν\barνγ$ off Z-resonance, and we discuss the constraints that these measurements can set on for the tau neutrino. We also derive limits for the Dirac case, when the presence of a vector charge radius is allowed. Finally, we comment on additional experimental data on $ν_μ$ scattering from the NuTeV, E734, CCFR and CHARM-II collaborations, and estimate the limits implied for and for the muon neutrino.

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Martin Hirsch, Enrico Nardi, Diego Restrepo. 2002-10-22. Bounds on the tau and muon neutrino vector and axial vector charge radius. https://doi.org/10.1103/physrevd.67.033005

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