Multiangle simulation of flavor evolution in the neutronization neutrino burst from an O-Ne-Mg core-collapse supernova

We report results of the first 3×3 ``multiangle'' simulation of the evolution of neutrino flavor in the core-collapse supernova environment. In particular, we follow neutrino flavor transformation in the neutronization neutrino burst of an O-Ne-Mg core-collapse event. Though in a qualitative sense our results are consistent with those obtained in 3×3 single-angle simulations, at least in terms of neutrino mass hierarchy dependence, performing multiangle calculations is found to reduce the adiabaticity of flavor evolution in the normal neutrino mass hierarchy, resulting in lower swap energies. Differences between single-angle and multiangle results are largest for the normal neutrino mass hierarchy. Our simulations also show that current uncertainties in the measured mass-squared and mixing angle parameters translate into uncertainties in neutrino swap energies. Our results show that at low θ₁₃ it may be difficult to resolve the neutrino mass hierarchy using the O-Ne-Mg neutronization neutrino burst.