Production of unstable heavy neutrinos in proto-neutron stars

Understand

We discuss the production of a class of heavy sterile neutrinos $\nu_h$ in proto-neutron stars.

• The neutrinos, of mass around $50$ MeV, have a negligible mixing with the active species but relatively large dimension-5 electromagnetic couplings.
• In particular, a magnetic dipole moment $\mu\approx 10^{-6}$ GeV$^{-1}$ implies that they are thermally produced through $e^+ e^-\to \bar \nu_h \nu_h$ in the early phase of the core collapse, whereas a heavy--light transition moment $\mu_{\rm tr}\approx 10^{-8}$ GeV$^{-1}$ allows their decay $\nu_h\to \nu_i \gamma$ with a lifetime around $10^{-3}$ s.
• This type of electromagnetic couplings has been recently proposed to explain the excess of electron-like events in baseline experiments.