Stars as Laboratories for Fundamental Physics - MPP Theory Group

468 Chapter 12
Fig. 12.8. Lower limit on τ γ /m ν for m ν ∼
< 40 eV and τtot /m ν ∼
> 5×10 5 s/eV
(most neutrinos pass the Earth before decaying).
Fig. 12.9. Upper limit on the radiative branching ratio B γ for m ν ∼
< 40 eV
and τ tot /m ν ∼
< 5×10 5 s/eV (most neutrinos decay between SN 1987A and
Earth).
shown in Fig. 12.9. The most conservative case yields approximately
B γ < 3×10 −10 . As a bound on an effective transition moment this is
µ eff < 0.7×10 −5 µ B m −2
eV (m eV /τ s ) 1/2 , (12.19)
where τ s = τ tot /s. Of course, if τ tot became so short that the neutrinos
would decay while still within the envelope of the progenitor even this