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Abstract |
Neutrino mixing parameters are measured exclusively below 1 TeV. We show, for the first time, how to translate the flavor composition of TeV-PeV astrophysical neutrinos into direct constraints on the standard mixing parameters, placing the high-energy regime on the same quantitative footing as sub-TeV global fits. Present 11.4-year IceCube Medium-Energy Starting Events data leave these parameters unconstrained, limited by flavor-measurement uncertainties, and an irreducible degeneracy between theta 12 and the unknown astrophysical neutrino production mechanism. However, upcoming multitelescope observations will resolve theta 23 and theta 13 with 17%-50% precision. While coarser than terrestrial precision, this marks the transition of TeV-PeV neutrinos from a qualitative consistency check to a genuine measurement of three-flavor mixing. Finally, we establish concrete benchmarks for detecting beyond-Standard-Model effects, providing a roadmap to probe new physics that grows with energy and remains invisible to terrestrial neutrino experiments. |
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