Characterization of the Three-Flavor Composition of Cosmic Neutrinos with IceCube

Icecube Collaboration

doi:10.1103/vntd-m133

Characterization of the Three-Flavor Composition of Cosmic Neutrinos with IceCube

Icecube Collaboration

Research output: Contribution to journal › Article › peer-review

Abstract

The flavor composition of cosmic neutrinos probes both the physical properties of their sources and oscillations over energies and distances unreachable by terrestrial experiments. Using 11.4 yr of IceCube data, we analyze the flavor composition of the all-sky neutrino flux from 5 TeV-10 PeV, significantly lowering the analysis threshold from a previous minimum of 35 TeV. The best-fit flavor fractions are fe,fμ,fτ=0.30-0.15+0.20, 0.37-0.16+0.14, 0.33-0.25+0.24. For the first time, we report that neutrinos of all three flavors are present in the observed cosmic neutrino flux at >90% confidence level. We infer the flavor composition at their sources, finding good agreement with pion decay while pure neutron decay is disfavored, with posterior probability 2.7×10-5 (∼4σ).

Original language	English (US)
Article number	081002
Journal	Physical Review Letters
Volume	137
Issue number	8
DOIs	https://doi.org/10.1103/vntd-m133
Publication status	Published - 21 Aug 2026
Externally published	Yes

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10.1103/vntd-m133

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@article{1197372c71fc46f48116223b5f1893c3,

title = "Characterization of the Three-Flavor Composition of Cosmic Neutrinos with IceCube",

abstract = "The flavor composition of cosmic neutrinos probes both the physical properties of their sources and oscillations over energies and distances unreachable by terrestrial experiments. Using 11.4 yr of IceCube data, we analyze the flavor composition of the all-sky neutrino flux from 5 TeV-10 PeV, significantly lowering the analysis threshold from a previous minimum of 35 TeV. The best-fit flavor fractions are fe,fμ,fτ=0.30-0.15+0.20, 0.37-0.16+0.14, 0.33-0.25+0.24. For the first time, we report that neutrinos of all three flavors are present in the observed cosmic neutrino flux at >90\% confidence level. We infer the flavor composition at their sources, finding good agreement with pion decay while pure neutron decay is disfavored, with posterior probability 2.7{\texttimes}10-5 (∼4σ).",

author = "\{Icecube Collaboration\} and R. Abbasi and M. Ackermann and J. Adams and Agarwalla, \{S. K.\} and Aguilar, \{J. A.\} and M. Ahlers and Alameddine, \{J. M.\} and S. Ali and Amin, \{N. M.\} and K. Andeen and C. Arg{\"u}elles and Y. Ashida and S. Athanasiadou and Axani, \{S. N.\} and R. Babu and X. Bai and J. Baines-Holmes and \{Balagopal V\}, A. and Barwick, \{S. W.\} and S. Bash and V. Basu and R. Bay and Beatty, \{J. J.\} and \{Becker Tjus\}, J. and P. Behrens and J. Beise and C. Bellenghi and B. Benkel and S. Benzvi and D. Berley and E. Bernardini and Besson, \{D. Z.\} and E. Blaufuss and L. Bloom and S. Blot and I. Bodo and F. Bontempo and \{Book Motzkin\}, \{J. Y.\} and \{Boscolo Meneguolo\}, C. and S. B{\"o}ser and O. Botner and J. B{\"o}ttcher and J. Braun and B. Brinson and Z. Brisson-Tsavoussis and Burley, \{R. T.\} and D. Butterfield and Campana, \{M. A.\} and K. Carloni and J. Carpio",

note = "Publisher Copyright: {\textcopyright} 2026 American Physical Society. ",

year = "2026",

month = aug,

day = "21",

doi = "10.1103/vntd-m133",

language = "English (US)",

volume = "137",

journal = "Physical Review Letters",

issn = "0031-9007",

publisher = "American Physical Society",

number = "8",

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TY - JOUR

T1 - Characterization of the Three-Flavor Composition of Cosmic Neutrinos with IceCube

AU - Icecube Collaboration

AU - Abbasi, R.

AU - Ackermann, M.

AU - Adams, J.

AU - Agarwalla, S. K.

AU - Aguilar, J. A.

AU - Ahlers, M.

AU - Alameddine, J. M.

AU - Ali, S.

AU - Amin, N. M.

AU - Andeen, K.

AU - Argüelles, C.

AU - Ashida, Y.

AU - Athanasiadou, S.

AU - Axani, S. N.

AU - Babu, R.

AU - Bai, X.

AU - Baines-Holmes, J.

AU - Balagopal V, A.

AU - Barwick, S. W.

AU - Bash, S.

AU - Basu, V.

AU - Bay, R.

AU - Beatty, J. J.

AU - Becker Tjus, J.

AU - Behrens, P.

AU - Beise, J.

AU - Bellenghi, C.

AU - Benkel, B.

AU - Benzvi, S.

AU - Berley, D.

AU - Bernardini, E.

AU - Besson, D. Z.

AU - Blaufuss, E.

AU - Bloom, L.

AU - Blot, S.

AU - Bodo, I.

AU - Bontempo, F.

AU - Book Motzkin, J. Y.

AU - Boscolo Meneguolo, C.

AU - Böser, S.

AU - Botner, O.

AU - Böttcher, J.

AU - Braun, J.

AU - Brinson, B.

AU - Brisson-Tsavoussis, Z.

AU - Burley, R. T.

AU - Butterfield, D.

AU - Campana, M. A.

AU - Carloni, K.

AU - Carpio, J.

PY - 2026/8/21

Y1 - 2026/8/21

N2 - The flavor composition of cosmic neutrinos probes both the physical properties of their sources and oscillations over energies and distances unreachable by terrestrial experiments. Using 11.4 yr of IceCube data, we analyze the flavor composition of the all-sky neutrino flux from 5 TeV-10 PeV, significantly lowering the analysis threshold from a previous minimum of 35 TeV. The best-fit flavor fractions are fe,fμ,fτ=0.30-0.15+0.20, 0.37-0.16+0.14, 0.33-0.25+0.24. For the first time, we report that neutrinos of all three flavors are present in the observed cosmic neutrino flux at >90% confidence level. We infer the flavor composition at their sources, finding good agreement with pion decay while pure neutron decay is disfavored, with posterior probability 2.7×10-5 (∼4σ).

AB - The flavor composition of cosmic neutrinos probes both the physical properties of their sources and oscillations over energies and distances unreachable by terrestrial experiments. Using 11.4 yr of IceCube data, we analyze the flavor composition of the all-sky neutrino flux from 5 TeV-10 PeV, significantly lowering the analysis threshold from a previous minimum of 35 TeV. The best-fit flavor fractions are fe,fμ,fτ=0.30-0.15+0.20, 0.37-0.16+0.14, 0.33-0.25+0.24. For the first time, we report that neutrinos of all three flavors are present in the observed cosmic neutrino flux at >90% confidence level. We infer the flavor composition at their sources, finding good agreement with pion decay while pure neutron decay is disfavored, with posterior probability 2.7×10-5 (∼4σ).

UR - https://www.scopus.com/pages/publications/105049062367

U2 - 10.1103/vntd-m133

DO - 10.1103/vntd-m133

M3 - Article

AN - SCOPUS:105049062367

SN - 0031-9007

VL - 137

JO - Physical Review Letters

JF - Physical Review Letters

IS - 8

M1 - 081002

ER -

Characterization of the Three-Flavor Composition of Cosmic Neutrinos with IceCube

Abstract

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