Spin flip of neutrinos with magnetic moment in core-collapse supernova

TL;DR

This paper investigates how neutrino magnetic moments can cause spin flips in supernovae, affecting neutrino signals and explosion dynamics, with implications for detecting neutrino properties and understanding supernova mechanisms.

Contribution

It provides detailed calculations of right-handed neutrino luminosity in supernovae and estimates detector sensitivities to neutrino magnetic moments, including new insights into Majorana neutrino effects.

Findings

Right-handed neutrino luminosity calculated up to 250 ms after bounce.

Super-Kamiokande can detect a few high-energy neutrino events from a galactic supernova for mu_Dirac=10^{-13}mu_B.

Spin flips may equilibrate electron neutrinos and non-electron antineutrinos if mu_Majorana~10^{-12}mu_B.

Abstract

Neutrino with magnetic moment can experience a chirality flip while scattering off charged particles. This effect may lead to important consequences for the dynamics and the neutrino signal of the core-collapse supernova. It is known that if neutrino is a Dirac fermion, then nu_L->nu_R transition induced by the chirality flip leads to the emission of sterile right-handed neutrinos. The typical energies of these neutrinos are rather high, E ~ (100-200)MeV. Neutrino spin precession in the magnetic field either inside the collapsing star or in the interstellar space may lead to the backward transition, nu_R->nu_L. Both possibilities are known to be interesting. In the former case high-energy neutrinos can deliver additional energy to the supernova envelope, which can help the supernova to explode. In the latter case high-energy neutrinos may be detected simultaneously with the "normal" supernova neutrino signal, which would be a smoking gun for the Dirac neutrino magnetic moment. We report the results of the calculation of the supernova right-handed neutrino luminosity up to 250 ms after bounce. They allow to refine the estimates of the energy emitted in right-handed neutrinos. Also the sensitivity of water Cherenkov detectors to the Dirac neutrino magnetic moment is estimated. For mu_Dirac=10^{-13}mu_B Super-Kamiokande is expected to detect at least few high-energy events from a galactic supernova explosion. Also we briefly discuss the case of Majorana neutrino magnetic moment. It is pointed out that spin flips may quickly equilibrate electron neutrinos with non-electron antineutrinos if mu_Majorana~10^{-12}mu_B. This may lead to various consequences for supernova physics.