Stars as Laboratories for Fundamental Physics - MPP Theory Group

Radiative Particle Decays 459
Fig. 12.4. Spectrum of photons from the solar neutrino decay ν e → ν ′ γ for
the indicated values of the anisotropy parameter α. Measurements of the
x-ray emission of the solar corona (open diamonds) according to Chodil et
al. (1965). Upper limit x- and γ-ray fluxes according to Frost et al. (1966)
and Peterson et al. (1966). Estimated albedo according to Peterson et al.
(1966). Thin solid line: Maximally allowed photon spectrum from neutrino
decay. (Figure adapted from Raffelt 1985.)
With Eq. (7.12) this translates into
µ eff < 5×10 −6 µ B m −2
eV . (12.10)
It must be stressed, again, that the recent progress in solar neutrino
astronomy has placed this result on the same footing as a terrestrial
experiment—the magnitude of the solar neutrino flux and its main
spectral features are now experimentally established!