Neutrinos change their quantum numbers “flavors” during their propagation. Such quantum phenomena are known as neutrino oscillations whose behaviors are sensitive to background medium. It is theoretically predicted that “collective neutrino oscillations” are caused by neutrino self-interactions deep inside core-collapse supernovae. However, there is no observational evidence of such non-linear flavor conversions. It seems that collective neutrino oscillations occur actively in electron capture supernovae because of their dilute density structure compared with that of standard iron core-collapse supernovae.
Dr. Sasaki, Dr. Takiwaki and their collaborators carried out numerical simulations of both hydrodynamics of an electron capture supernova and neutrino oscillations inside the supernova. Then, they estimated event numbers of neutrinos and time evolutions of hardness ratios in future neutrino detectors such as Hyper-Kamiokande (HK) and DUNE. They found that the contribution of collective neutrino oscillations can be distinguished observationally in such neutrino detectors if the electron capture supernova occurs within 〜10 kpc.
Hirokazu Sasaki [hiro.sasaki ATM nao.ac.jp]
Tomoya Takiwaki [personal website]