Characterization of the Three-Flavor Composition of Cosmic Neutrinos with IceCube
Journal article, 2026

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 f(e); f(mu); f(tau) = 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 & times; 10(-5) (similar to 4 sigma).

Author

R. Abbasi

Loyola University of Chicago

M. Ackermann

Deutsches Elektronen-Synchrotron (DESY)

J. Adams

University of Canterbury

S. K. Agarwalla

University of Wisconsin Madison

Institute of Physics Bhubaneswar

J. A. Aguilar

Université libre de Bruxelles (ULB)

S. Ali

University of Kansas

N. M. Amin

University of Delaware

K. Andeen

Marquette University

C. Arguelles

Harvard University

Y. Ashida

University of Utah

S. Athanasiadou

Deutsches Elektronen-Synchrotron (DESY)

S. N. Axani

University of Delaware

X. Bai

South Dakota School of Mines & Technology

J. Baines-Holmes

University of Wisconsin Madison

V. A. Balagopal

University of Delaware

University of Wisconsin Madison

S. W. Barwick

University of California

S. Bash

Technical University of Munich

V. Basu

University of Utah

R. Bay

University of California

J. J. Beatty

Ohio State University

J. Becker Tjus

P. Behrens

RWTH Aachen University

C. Bellenghi

Technical University of Munich

B. Benkel

Deutsches Elektronen-Synchrotron (DESY)

D. Berley

University of Maryland

E. Bernardini

National Institute for Nuclear Physics

University of Padua

D. Z. Besson

University of Kansas

E. Blaufuss

University of Maryland

L. Bloom

University of Alabama

S. Blot

Deutsches Elektronen-Synchrotron (DESY)

I. Bodo

University of Wisconsin Madison

F. Bontempo

Karlsruhe Institute of Technology (KIT)

J. Y. Book Motzkin

Harvard University

C. Boscolo Meneguolo

National Institute for Nuclear Physics

University of Padua

S. Boser

Johannes Gutenberg University Mainz

J. Bottcher

RWTH Aachen University

J. Braun

University of Wisconsin Madison

B. Brinson

Georgia Institute of Technology

Z. Brisson-Tsavoussis

Queen's University

R. T. Burley

University of Adelaide

D. Butterfield

University of Wisconsin Madison

M. A. Campana

Drexel University

K. Carloni

Harvard University

J. Carpio

University of Nevada, Las Vegas

S. Chattopadhyay

University of Wisconsin Madison

Institute of Physics Bhubaneswar

N. Chau

Université libre de Bruxelles (ULB)

Z. Chen

State University of New York

D. Chirkin

University of Wisconsin Madison

S. Choi

University of Utah

B. A. Clark

University of Maryland

P. Coleman

RWTH Aachen University

G. H. Collin

Massachusetts Institute of Technology (MIT)

D. A. Coloma Borja

University of Padua

A. Connolly

Ohio State University

J. M. Conrad

Massachusetts Institute of Technology (MIT)

D. F. Cowen

Pennsylvania State University

C. De Clercq

Vrije Universiteit Brussel (VUB)

J. J. DeLaunay

Pennsylvania State University

D. Delgado

Harvard University

T. Delmeulle

Université libre de Bruxelles (ULB)

S. Deng

RWTH Aachen University

P. Desiati

University of Wisconsin Madison

K. D. de Vries

Vrije Universiteit Brussel (VUB)

G. de Wasseige

Universite catholique de Louvain

J. C. Diaz-Velez

University of Wisconsin Madison

T. Ding

University of Nevada, Las Vegas

M. Dittmer

University of Münster

A. Domi

University of Erlangen-Nuremberg (FAU)

L. Draper

University of Utah

L. Dueser

RWTH Aachen University

D. Durnford

University of Alberta

K. Dutta

Johannes Gutenberg University Mainz

M. A. DuVernois

University of Wisconsin Madison

T. Ehrhardt

Johannes Gutenberg University Mainz

L. Eidenschink

Technical University of Munich

A. Eimer

University of Erlangen-Nuremberg (FAU)

P. Eller

Technical University of Munich

R. Engel

Karlsruhe Institute of Technology (KIT)

H. Erpenbeck

University of Wisconsin Madison

W. Esmail

University of Münster

S. Eulig

Harvard University

J. Evans

University of Maryland

P. A. Evenson

University of Delaware

K. L. Fan

University of Maryland

K. Fang

University of Wisconsin Madison

K. Farrag

Chiba University

A. R. Fazely

Southern University and A&M College

A. Fedynitch

Academia Sinica

N. Feigl

Humboldt University of Berlin

C. Finley

Stockholm University

L. Fischer

Deutsches Elektronen-Synchrotron (DESY)

D. Fox

Pennsylvania State University

A. Franckowiak

Ruhr-Universität Bochum

S. Fukami

Deutsches Elektronen-Synchrotron (DESY)

P. Furst

RWTH Aachen University

J. Gallagher

University of Wisconsin Madison

E. Ganster

RWTH Aachen University

A. Garcia

Harvard University

M. Garcia

University of Delaware

G. Garg

University of Wisconsin Madison

Institute of Physics Bhubaneswar

E. Genton

Universite catholique de Louvain

Harvard University

L. Gerhardt

Lawrence Berkeley National Laboratory

A. Ghadimi

University of Alabama

J. G. Gonzalez

University of Delaware

S. Goswami

University of Nevada, Las Vegas

D. Grant

Simon Fraser University

S. J. Gray

University of Maryland

S. Griffin

University of Wisconsin Madison

D. Guevel

University of Wisconsin Madison

C. Gunther

RWTH Aachen University

C. Ha

Chung-Ang University

C. Haack

University of Erlangen-Nuremberg (FAU)

L. Halve

RWTH Aachen University

F. Halzen

University of Wisconsin Madison

L. Hamacher

RWTH Aachen University

M. Ha Minh

Technical University of Munich

M. Handt

RWTH Aachen University

K. Hanson

University of Wisconsin Madison

J. Hardin

Massachusetts Institute of Technology (MIT)

P. Hatch

Queen's University

A. Haungs

Karlsruhe Institute of Technology (KIT)

J. Haussler

RWTH Aachen University

J. Hellrung

Ruhr-Universität Bochum

L. Hennig

University of Erlangen-Nuremberg (FAU)

F. Henningsen

Simon Fraser University

L. Heuermann

RWTH Aachen University

R. Hewett

University of Canterbury

A. Hidvegi

Stockholm University

C. Hill

Chiba University

G. c. Hill

University of Adelaide

R. Hmaid

Chiba University

K. D. Hoffman

University of Maryland

D. Hooper

University of Wisconsin Madison

S. Hori

University of Wisconsin Madison

K. Hoshina

University of Wisconsin Madison

University of Tokyo

M. Hostert

Harvard University

W. Hou

Karlsruhe Institute of Technology (KIT)

M. Hrywniak

Stockholm University

T. Huber

Karlsruhe Institute of Technology (KIT)

K. Hultqvist

Stockholm University

K. Hymon

Academia Sinica

A. Ishihara

Chiba University

W. Iwakiri

Chiba University

S. Jain

University of Wisconsin Madison

O. Janik

University of Erlangen-Nuremberg (FAU)

M. Jansson

Universite catholique de Louvain

M. Jeong

University of Utah

M. Jin

Harvard University

N. Kamp

Harvard University

D. Kang

Karlsruhe Institute of Technology (KIT)

W. Kang

Drexel University

A. Kappes

University of Münster

T. Karg

Deutsches Elektronen-Synchrotron (DESY)

M. Karl

Technical University of Munich

A. Karle

University of Wisconsin Madison

A. Katil

University of Alberta

M. Kauer

University of Wisconsin Madison

J. L. Kelley

University of Wisconsin Madison

M. Khanal

University of Utah

A. Khatee Zathul

University of Wisconsin Madison

A. Kheirandish

University of Nevada, Las Vegas

H. Kimku

Chung-Ang University

J. Kiryluk

State University of New York

C. Klein

University of Erlangen-Nuremberg (FAU)

S. R. Klein

Lawrence Berkeley National Laboratory

University of California

Y. Kobayashi

Chiba University

R. Koirala

University of Delaware

H. Kolanoski

Humboldt University of Berlin

T. Kontrimas

Technical University of Munich

L. Kopke

Johannes Gutenberg University Mainz

C. Kopper

University of Erlangen-Nuremberg (FAU)

P. Koundal

University of Delaware

M. Kowalski

Humboldt University of Berlin

Deutsches Elektronen-Synchrotron (DESY)

A. Kravka

University of Utah

N. Krieger

Ruhr-Universität Bochum

J. Krishnamoorthi

University of Wisconsin Madison

T. Krishnan

Harvard University

K. Kruiswijk

Universite catholique de Louvain

A. Kumar

Deutsches Elektronen-Synchrotron (DESY)

E. Kun

Ruhr-Universität Bochum

N. Kurahashi

Drexel University

N. Lad

Deutsches Elektronen-Synchrotron (DESY)

C. Lagunas Gualda

Technical University of Munich

L. Lallement Arnaud

Université libre de Bruxelles (ULB)

M. Lamoureux

Universite catholique de Louvain

M. J. Larson

University of Maryland

J. P. Lazar

Universite catholique de Louvain

A. Leszczynska

University of Delaware

J. Liao

Georgia Institute of Technology

C. Lin

University of Delaware

Q. R. Liu

Simon Fraser University

M. Liubarska

University of Alberta

C. Love

Drexel University

L. Lu

University of Wisconsin Madison

F. Lucarelli

University of Geneva

W. Luszczak

Ohio State University

Y. Lyu

University of California

Lawrence Berkeley National Laboratory

M. Macdonald

Harvard University

J. Madsen

University of Wisconsin Madison

E. Magnus

Vrije Universiteit Brussel (VUB)

Y. Makino

University of Wisconsin Madison

E. Manao

Technical University of Munich

S. Mancina

National Institute for Nuclear Physics

University of Padua

A. Mand

University of Wisconsin Madison

I. C. Mari

Université libre de Bruxelles (ULB)

S. Marka

Columbia University

Z. Marka

Columbia University

L. Marten

RWTH Aachen University

I. Martinez-Soler

Harvard University

R. Maruyama

Yale University

J. Mauro

Universite catholique de Louvain

F. McNally

Mercer University

K. Meagher

University of Wisconsin Madison

S. Mechbal

Deutsches Elektronen-Synchrotron (DESY)

A. Medina

Ohio State University

M. Meier

Chiba University

Y. Merckx

Vrije Universiteit Brussel (VUB)

L. Merten

Ruhr-Universität Bochum

J. Mitchell

Southern University and A&M College

L. Molchany

South Dakota School of Mines & Technology

S. Mondal

University of Utah

T. Montaruli

University of Geneva

R. W. Moore

University of Alberta

Y. Morii

Chiba University

A. Mosbrugger

University of Erlangen-Nuremberg (FAU)

M. Moulai

University of Wisconsin Madison

D. Mousadi

Deutsches Elektronen-Synchrotron (DESY)

E. Moyaux

Universite catholique de Louvain

T. Mukherjee

Karlsruhe Institute of Technology (KIT)

R. Naab

Deutsches Elektronen-Synchrotron (DESY)

M. Nakos

University of Wisconsin Madison

J. Necker

Deutsches Elektronen-Synchrotron (DESY)

L. Neste

Stockholm University

M. Neumann

University of Münster

K. Noda

Chiba University

A. Noell

RWTH Aachen University

A. Novikov

University of Delaware

A. Obertacke

Stockholm University

V. O'Dell

University of Wisconsin Madison

A. Olivas

University of Maryland

R. Orsoe

Technical University of Munich

J. Osborn

University of Wisconsin Madison

V. Palusova

Johannes Gutenberg University Mainz

H. Pandya

University of Delaware

A. Parenti

Université libre de Bruxelles (ULB)

N. Park

Queen's University

E. N. Paudel

University of Alabama

L. Paul

South Dakota School of Mines & Technology

T. Pernice

Deutsches Elektronen-Synchrotron (DESY)

J. Peterson

University of Wisconsin Madison

M. Plum

South Dakota School of Mines & Technology

V. Poojyam

University of Alabama

Y. Popovych

Johannes Gutenberg University Mainz

M. Prado Rodriguez

University of Wisconsin Madison

R. Procter-Murphy

University of Maryland

G. T. Przybylski

Lawrence Berkeley National Laboratory

L. Pyras

University of Utah

C. Raab

Universite catholique de Louvain

J. Rack-Helleis

Johannes Gutenberg University Mainz

N. Rad

Deutsches Elektronen-Synchrotron (DESY)

K. Rawlins

University of Alaska Anchorage

Z. Rechav

University of Wisconsin Madison

A. Rehman

University of Delaware

I. Reistroffer

South Dakota School of Mines & Technology

E. Resconi

Technical University of Munich

S. Reusch

Deutsches Elektronen-Synchrotron (DESY)

C. D. Rho

Sungkyunkwan University

L. Ricca

Universite catholique de Louvain

B. Riedel

University of Wisconsin Madison

E. J. Roberts

University of Adelaide

M. Rongen

University of Erlangen-Nuremberg (FAU)

A. Rosted

Chiba University

C. Rott

University of Utah

L. Ruohan

Technical University of Munich

D. Ryckbosch

Ghent university

P. Sampathkumar

Karlsruhe Institute of Technology (KIT)

M. Santander

University of Alabama

S. Sarkar

University of Oxford

M. Scarnera

Universite catholique de Louvain

P. Schaile

Technical University of Munich

M. Schaufel

RWTH Aachen University

H. Schieler

Karlsruhe Institute of Technology (KIT)

S. Schindler

University of Erlangen-Nuremberg (FAU)

L. Schlickmann

Johannes Gutenberg University Mainz

B. Schluter

University of Münster

F. Schluter

Université libre de Bruxelles (ULB)

T. Schmidt

University of Maryland

F. G. Schroder

University of Delaware

Karlsruhe Institute of Technology (KIT)

L. Schumacher

University of Erlangen-Nuremberg (FAU)

S. Schwirn

RWTH Aachen University

S. Sclafani

University of Maryland

D. Seckel

University of Delaware

L. Seen

University of Wisconsin Madison

M. Seikh

University of Kansas

S. Seunarine

University of Wisconsin

P. A. Sevle Myhr

Universite catholique de Louvain

R. Shah

Drexel University

N. Shimizu

Chiba University

B. Skrzypek

University of California

R. Snihur

University of Wisconsin Madison

J. Soedingrekso

Ghent university

A. Sogaard

Ohio State University

D. Soldin

University of Delaware

P. Soldin

Lawrence Berkeley National Laboratory

G. M. Spiczak

University of Maryland

C. Spiering

Georgia Institute of Technology

J. Stachurska

Ghent university

M. Stamatikos

Ohio State University

T. Stanev

University of Delaware

T. Stezelberger

Lawrence Berkeley National Laboratory

G. W. Sullivan

University of Maryland

I. Taboada

Georgia Institute of Technology

S. Ter-Antonyan

Southern University and A&M College

A. Terliuk

Technical University of Munich

A. Thakuri

South Dakota School of Mines & Technology

M. Thiesmeyer

University of Wisconsin Madison

W. G. Thompson

Harvard University

J. Thwaites

University of Wisconsin Madison

S. Tilav

University of Delaware

S. Toscano

Université libre de Bruxelles (ULB)

D. Tosi

University of Wisconsin Madison

A. Trettin

Deutsches Elektronen-Synchrotron (DESY)

A. K. Upadhyay

University of Wisconsin Madison

Institute of Physics Bhubaneswar

K. Upshaw

Southern University and A&M College

A. Vaidyanathan

Marquette University

N. Valtonen-Mattila

Ruhr-Universität Bochum

J. Valverde

Marquette University

J. Vandenbroucke

University of Wisconsin Madison

T. Van Eeden

Deutsches Elektronen-Synchrotron (DESY)

N. van Eijndhoven

Vrije Universiteit Brussel (VUB)

J. van Santen

Deutsches Elektronen-Synchrotron (DESY)

J. Vara

University of Münster

M. Venugopal

Karlsruhe Institute of Technology (KIT)

M. Vereecken

Universite catholique de Louvain

S. Vergara Carrasco

University of Canterbury

S. Verpoest

University of Delaware

D. Veske

Columbia University

A. Vijai

University of Maryland

J. Villarreal

Massachusetts Institute of Technology (MIT)

C. Walck

Stockholm University

A. Wang

Georgia Institute of Technology

E. H. S. Warrick

Southern University and A&M College

P. Weigel

Massachusetts Institute of Technology (MIT)

A. Weindl

Karlsruhe Institute of Technology (KIT)

J. Weldert

Johannes Gutenberg University Mainz

A. Y. Wen

Harvard University

C. Wendt

University of Wisconsin Madison

M. Weyrauch

Karlsruhe Institute of Technology (KIT)

C. H. Wiebusch

RWTH Aachen University

D. R. Williams

University of Alabama

M. Wolf

Technical University of Munich

G. Wrede

University of Erlangen-Nuremberg (FAU)

X. W. Xu

Southern University and A&M College

J. P. Yanez

University of Alberta

Y. Yao

University of Wisconsin Madison

E. Yildizci

University of Wisconsin Madison

S. Yoshida

Chiba University

R. Young

University of Kansas

F. Yu

Harvard University

S. Yu

University of Utah

T. Yuan

University of Wisconsin Madison

S. Yun-Carcamo

Drexel University

A. Zander Jurowitzki

Technical University of Munich

A. Zegarelli

Ruhr-Universität Bochum

Z. Zhang

State University of New York

P. Zhelnin

Harvard University

P. Zilberman

University of Wisconsin Madison

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 137 8 081002

Subject Categories (SSIF 2025)

Subatomic Physics

DOI

10.1103/vntd-m133

More information

Latest update

9/4/2026 1