Collective Flavor Oscillations Of Supernova Neutrinos and r-Process Nucleosynthesis

TL;DR

This paper investigates how collective neutrino flavor oscillations in supernovae, influenced by initial spectral conditions and neutrino hierarchy, affect r-process nucleosynthesis by altering the electron fraction.

Contribution

It analyzes the occurrence of spectral splits in neutrino spectra under various initial conditions and their impact on r-process nucleosynthesis constraints.

Findings

Spectral splits depend on initial flux ratios and energy spectra models.

Variations in spectral splits influence the electron fraction $Y_e$ in supernovae.

Constraints on initial spectral conditions are derived for successful r-process nucleosynthesis.

Abstract

Neutrino-neutrino interactions inside core-collapse supernovae may give rise to collective flavor oscillations resulting in swap between flavors. These oscillations depend on the initial energy spectra, and relative fluxes or relative luminosities of the neutrinos. It has been observed that departure from energy equipartition among different flavors can give rise to one or more sharp spectral swap over energy, termed as splits. We study the occurrence of splits in the neutrino and antineutrino spectra, varying the initial relative fluxes for different models of initial energy spectrum, in both normal and inverted hierarchy. These initial relative flux variations give rise to several possible split patterns whereas variation over different models of energy spectra give similar results. We explore the effect of these spectral splits on the electron fraction, $Y_e$, that governs r-process nucleosynthesis inside supernovae. Since spectral splits modify the electron neutrino and antineutrino spectra in the region where r-process is postulated to happen, and since the pattern of spectral splits depends on the initial conditions of the spectra and the neutrino mass hierarchy, we show that the condition $Y_e < 0.5$ required for successful r-process nucleosynthesis will lead to constraints on the initial spectral conditions, for a given neutrino mass hierarchy.