TAPIR Seminar

Over the past decades our knowledge of neutrino flavor evolution has improved significantly. Our new understanding of matter resonances in the sun explained the apparent deficit in the observed number of solar neutrinos. Recently, it has become clear that in addition to the matter enhancement of flavor conversions, a new interaction will arise when the neutrino density is sufficiently high. A neutrino density of the right magnitude can be found in the early stages of core-collapse supernovae. Close to the proto-neutron star the neutrino self-interactions lead to collective flavor transformations. Further out in the supernova the matter densities are such that Mikheyev-Smirnov-Wolfenstein (MSW) resonances add their contribution to the neutrino flavor evolution. If the supernova matter is turbulent, as is expected from multidimensional supernova simulations, another layer is added to the intricate flavor evolution problem.

In this talk I will briefly outline the components needed to calculate the flavor evolution of a neutrino as it propagates from its production site at the proto-neutron star's surface through the supernova until it reaches Earth. The main focus of the talk will be on the signatures arising in the neutrino matter state survival probabilities due to the neutrino self-interactions, the matter enhanced flavor conversions, and the changes that appears in these signatures when the matter, through which the neutrino travels, is turbulent. Depending upon the hierarchy and the properties of the turbulence, the neutrino spectral signatures of collective effects and/or shock waves in the supernova may be smothered to the point where they are unobservable in the "golden" channels (νe → νμ transitions) of the neutrino signal from the next galactic core-collapse supernova. Fortunately, when these features are completely obscured the large turbulence engenders signatures of its own in neutrino mixing channels where no effects previously existed. The observability of the predicted spectral features in a future neutrino detection at Earth will be addressed briefly at the end of the talk.