NBIA Seminar: Rasmus S. L. Hansen – Niels Bohr Institute - University of Copenhagen

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NBIA Seminar: Rasmus S. L. Hansen

(MPI, Heidelberg)

The onset of neutrino oscillations in supernovae

The existence of neutrino oscillations is well established and the associated neutrino flavour conversion (e.g. from electron to muon neutrinos) has been observed for neutrinos from accelerators, nuclear reactors, the atmosphere and the Sun. For solar neutrinos, the effect of a large background of electrons on the neutrino flavour state is key to our theoretical understanding. In the case of a supernova, the density is many orders of magnitude larger than in the Sun. In addition, the density of neutrinos is very large, and the Hamiltonian describing the neutrino flavour evolution depends on the neutrino state itself. In some cases this leads to flavour conversion with exponentially growth which can significantly alter the neutrino signal from a supernova as well as the nucleosynthesis yield. In this talk, I will focus on the initial evolution of supernova neutrinos - both the initial evolution inside the region of neutrino emission and the initial part of the exponentially growing conversion.