Neutrino magnetic moment signatures in the supernova neutrino signal

TL;DR

This paper explores how neutrino magnetic moments could produce detectable high-energy neutrino signals from supernovae, offering a potential method to measure or constrain neutrino magnetic properties.

Contribution

It introduces a novel observational signature of neutrino magnetic moments in supernova neutrino signals and discusses how to extract magnetic moment values from such observations.

Findings

High-energy neutrino signals could indicate neutrino magnetic moments rom supernovae.

Detection thresholds depend on the magnetic moment magnitude and detector scale.

Additional neutrino deficits could help determine the magnetic moment value.

Abstract

It is known that if neutrino is a Dirac fermion with magnetic moment, then \nu_L -> \nu_R -> \nu_L transition of supernova neutrinos may occur. The first stage of such transition is due to the neutrino spin flip inside the hot dense supernova core, while the second one - due to the neutrino spin precession in the galactic magnetic field on the way from the supernova to terrestrial detectors. This can result in the detection of 60-200 MeV neutrinos simultaneously with the "normal" supernova neutrino signal, which would be a smoking gun for the Dirac neutrino magnetic moment, \mu. We argue that in case of a nearby supernova explosion (~10 kpc away from the Earth) one may observe such high-energy events in Super-Kamiokande if \mu \gtrsim 10^{-13} \mu_B, and in a Mt-scale detector if \mu \gtrsim 0.5*10^{-13} \mu_B. Such an observation by itself, however, may be not sufficient to determine the value of the magnetic moment, because of the ignorance of the interstellar magnetic field. We point out that if in addition a deficit of the neutronization burst neutrinos is established, it would be possible to extract the value of the magnetic moment from observations. We also briefly discuss a possible Majorana magnetic moment signature due to \nu_e -> \bar{\nu}_{\mu,\tau} flip inside the supernova core.