# 2019-05-08

Title: Detectability of collective neutrino oscillations in core-collapse supernovae

Hirokazu Sasaki (University of Tokyo, NAOJ)

abstract:

Neutrinos are elementary particles produced through weak interactions. In our nature, there are many sources of neutrinos, for example, the Sun, atmosphere of the earth, core-collapse supernovae and blazars. Neutrinos emitted from there change their flavors during the propagation. This phenomenon is called neutrino oscillations. Behaviors of such flavor transitions are sensitive to refractive effect of background electrons and neutrinos themselves. In core-collapse supernovae, large numbers of neutrinos are produced and emitted from the proto-neutron star after core-bounce. It is considered that coherent scatterings of self-interacting neutrinos induce collective neutrino oscillations near the proto-neutron star ~100 km, which is expected to affect supernova explosion and nucleosynthesis. However, a signature of such non-linear flavor conversions has not been found in observations.

In this talk, we show numerical results of collective neutrino oscillations in electron-capture supernovae. We also discuss detectability of collective neutrino oscillations in neutrino observatories such as Hyper-Kamiokande (HK) and DUNE.  A hardness ratio between a number of high energy (anti) neutrinos and low energy one traces neutrino spectral swap caused by collective neutrino oscillations. In inverted neutrino mass hierarchy, we find the hardness ratio of electron antineutrinos becomes softer. Such trend can be distinguished in HK if the distance to the supernova is 10 kpc. In normal neutrino mass hierarchy, the hardness ratio of electron type neutrino becomes softer. DUNE can clarify this effect if the explosion occurs within 2 kpc.

host contact: Masato Shirasaki