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Measuring neutrino mixing above 1 TeV with astrophysical neutrinos

Mauricio Bustamante1,*, Qinrui Liu2,3,4,5,†, and Gabriela Barenboim6,‡

  • *Contact author: mbustamante@nbi.ku.dk
  • †Contact author: qinrui_liu@sfu.ca
  • ‡Contact author: gabriela.barenboim@uv.es
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Phys. Rev. D 114, 083005 – Published 2 October, 2026

DOI: https://doi.org/10.1103/76bd-86sg

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 θ12 and the unknown astrophysical neutrino production mechanism. However, upcoming multitelescope observations will resolve θ23 and θ13 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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Phys. Rev. D 114, 083005– Published 2 October, 2026
  • Received 14 March 2026
  • Revised 16 July 2026
  • Accepted 8 September 2026
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