Multi-Angle Simulation of Flavor Evolution in the Neutrino Neutronization Burst From an O-Ne-Mg Core-Collapse Supernova

We report results of the first 3-by-3 "multi-angle" 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-by-3 single-angle simulations, at least in terms of neutrino mass hierarchy dependence, performing multi-angle 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 multi-angle 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 theta-13 it may be difficult to resolve the neutrino mass hierarchy using the O-Ne-Mg neutronization neutrino burst.