Flavor Physics of High Energy Astrophysical Neutrinos

The development of km-scale neutrino telescopes is now realizing the neutrino astronomy. Astrophysical high energy neutrinos have been considered crucial for understanding the origin of ultra high energy cosmic rays and expected to provide a parallel observation on exotic object in the universe such as gamma ray bursts, active galactic nuclei and supernovae. Capable of identifying neutrino flavors, new generation telescopes will provide a parallel test of neutrino physics as well as astrophysics. This capability stimulates the flavor astronomy. In this emerging field, only the canonical pion source and the standard oscillation are mostly investigated while others are little discussed. In this research, we will not only study different kinds of astrophysical neutrino sources and various flavor transition models but also investigate their interplay. By studying flavor ratios rendered from different sources in different scenarios, we can infer the property of the source and test flavor transition models and mixing parameters with the neutrino telescope observation. If the measurement results in a flavor ratio much different from the canonical 1:1:1, it will be very interesting. We either find a different source (e.g. the tau source) or confirm a non-standard physics (e.g. neutrino decays). To measure the neutrino flavor ratio to sufficient precision requires neutrino telescopes to have capability to discriminate muon and tau neutrinos for, at such high energies, both will trigger similar track events within the detector. We simulate the sub-showers generation on the track as muons or taus traverse the detector. Once the detector measures radio signals produced by these sub-showers, the flavor can be inferred by comparing the measured track pattern with the database established from our simulation. In the near future, neutrino telescopes should score certain number of astrophysical high energy neutrino events and we can then test and review our work.

Project ID:PA10101-1176
External Project ID:NSC100-2112-M182-001-MY3