Triggering collective oscillations by three-flavor effects

TL;DR

This paper investigates how three-flavor effects, such as radiative corrections and flux differences, influence collective neutrino oscillations in supernovae, showing that even tiny effects can trigger flavor conversions regardless of theta_13.

Contribution

It demonstrates that small three-flavor perturbations can break the two-flavor approximation, leading to flavor conversions independent of the value of theta_13.

Findings

Small three-flavor effects trigger collective oscillations.

Flavor evolution depends on neutrino spectra and mass ordering.

Conversion occurs even at extremely small theta_13 values.

Abstract

Collective flavor transformations in supernovae, caused by neutrino-neutrino interactions, are essentially a two-flavor phenomenon driven by the atmospheric mass difference and the small mixing angle theta_13. In the two-flavor approximation, the initial evolution depends logarithmically on theta_13 and the system remains trapped in an unstable fixed point for theta_13 = 0. However, any effect breaking exact nu_mu-nu_tau equivalence triggers the conversion. Such three-flavor perturbations include radiative corrections to weak interactions, small differences between the nu_mu and nu_tau fluxes, or non-standard interactions. Therefore, extremely small values of theta_13 are in practice equivalent, the fate of the system depending only on the neutrino spectra and their mass ordering.