Neutrino oscillations in magnetically driven supernova explosions

TL;DR

This paper explores how magnetically driven supernova explosions affect neutrino oscillations and spectra, revealing potential observational signatures linked to magnetic explosion mechanisms and magnetar formation.

Contribution

It provides the first detailed numerical analysis of neutrino flavor conversion in non-spherical, magnetically driven supernova environments, highlighting anisotropic effects on neutrino signals.

Findings

Neutrino survival probabilities vary significantly with direction in MHD supernovae.

Shock passage causes steep decreases in electron antineutrino event numbers from the polar direction.

Magnetic explosion features lead to early shock arrival in resonance regions, affecting neutrino signals.

Abstract

We investigate neutrino oscillations from core-collapse supernovae that produce magnetohydrodynamic (MHD) explosions. By calculating numerically the flavor conversion of neutrinos in the highly non-spherical envelope, we study how the explosion anisotropy has impacts on the emergent neutrino spectra through the Mikheyev-Smirnov-Wolfenstein effect. In the case of the inverted mass hierarchy with a relatively large theta_(13), we show that survival probabilities of electron type neutrinos and antineutrinos seen from the rotational axis of the MHD supernovae (i.e., polar direction), can be significantly different from those along the equatorial direction. The event numbers of electron type antineutrinos observed from the polar direction are predicted to show steepest decrease, reflecting the passage of the magneto-driven shock to the so-called high-resonance regions. Furthermore we point out that such a shock effect, depending on the original neutrino spectra, appears also for the low-resonance regions, which leads to a noticeable decrease in the electron type neutrino signals. This reflects a unique nature of the magnetic explosion featuring a very early shock-arrival to the resonance regions, which is in sharp contrast to the neutrino-driven delayed supernova models. Our results suggest that the two features in the electron type antineutrinos and neutrinos signals, if visible to the Super-Kamiokande for a Galactic supernova, could mark an observational signature of the magnetically driven explosions, presumably linked to the formation of magnetars and/or long-duration gamma-ray bursts.