Spin-flavor precession of Dirac neutrinos in dense matter and its potential in core-collapse supernovae

TL;DR

This paper investigates the spin-flavor precession of Dirac neutrinos in dense matter under strong magnetic fields, highlighting conditions where this process is enhanced and its potential implications in core-collapse supernovae.

Contribution

It provides the first detailed analysis of Dirac neutrino spin-flavor precession in supernova environments, considering magnetic moments and matter effects, and compares it with Majorana neutrinos.

Findings

SFP of Dirac neutrinos occurs near electron fraction 1/3

Required magnetic field strength for Dirac neutrinos is around 10^14 G

SFP sensitivity depends on supernova simulation details

Abstract

We calculate the spin-flavor precession (SFP) of Dirac neutrinos induced by strong magnetic fields and finite neutrino magnetic moments in dense matter. As found in the case of Majorana neutrinos, the SFP of Dirac neutrinos is enhanced by the large magnetic field potential and suppressed by large matter potentials composed of the baryon density and the electron fraction. The SFP is possible irrespective of the large baryon density when the electron fraction is close to 1/3. The diagonal neutrino magnetic moments that are prohibited for Majorana neutrinos enable the spin precession of Dirac neutrinos without any flavor mixing. With supernova hydrodynamics simulation data, we discuss the possibility of the SFP of both Dirac and Majorana neutrinos in core-collapse supernovae. The SFP of Dirac neutrinos occurs at a radius where the electron fraction is 1/3. The required magnetic field of the proto-neutron star for the SFP is a few $10^{14}$G at any explosion time. For the Majorana neutrinos, the required magnetic field fluctuates from $10^{13}$G to $10^{15}$G. Such a fluctuation of the magnetic field is more sensitive to the numerical scheme of the neutrino transport in the supernova simulation.