Speaker
Description
High-energy cosmic neutrinos, with energies in the TeV-PeV range, provide a way to push the energy frontier of particle physics. Their flavor composition --- the relative contribution of each neutrino flavor in the total flux --- is a powerful observable that is unique to neutrinos. The flavor composition detected at Earth depends on the neutrino production process --- and so can probe the astrophysics of the sources --- and on the flavor transitions that the neutrinos undergo en route to Earth --- and so can probe neutrino physics. Because many high-energy new-physics models propose significant modifications to the flavor composition, there is a large potential to test neutrino physics by measuring the flavor composition with increasing precision. Representative new-physics models include unstable neutrinos, new neutrino interactions, sterile neutrinos, and the violation of fundamental symmetries. We will show concrete examples that illustrate how the tests of particle physics physics --- and of astrophysics --- via the flavor composition are accessible already today, and how the coming decade may extend these tests to energies a thousandfold higher.
