Search for Extremely-High-Energy Neutrinos and First Constraints on the Ultrahigh-Energy Cosmic-Ray Proton Fraction with IceCube

doi:10.1103/PhysRevLett.135.031001

. 2025 Jul 18;135(3):031001.

doi: 10.1103/PhysRevLett.135.031001.

Search for Extremely-High-Energy Neutrinos and First Constraints on the Ultrahigh-Energy Cosmic-Ray Proton Fraction with IceCube

R Abbasi¹, M Ackermann², J Adams³, S K Agarwalla⁴, J A Aguilar⁵, M Ahlers⁶, J M Alameddine⁷, N M Amin⁸, K Andeen⁹, C Argüelles¹⁰, Y Ashida¹¹, S Athanasiadou², S N Axani⁸, R Babu¹², X Bai¹³, A Balagopal V⁴, M Baricevic⁴, S W Barwick¹⁴, S Bash¹⁵, V Basu⁴, R Bay¹⁶, J J Beatty^{17

18}, J Becker Tjus¹⁹, J Beise²⁰, C Bellenghi¹⁵, S BenZvi²¹, D Berley²², E Bernardini²³, D Z Besson²⁴, E Blaufuss²², L Bloom²⁵, S Blot², F Bontempo²⁶, J Y Book Motzkin¹⁰, C Boscolo Meneguolo²³, S Böser²⁷, O Botner²⁰, J Böttcher²⁸, J Braun⁴, B Brinson²⁹, Z Brisson-Tsavoussis³⁰, J Brostean-Kaiser², L Brusa²⁸, R T Burley³¹, D Butterfield⁴, M A Campana³², I Caracas²⁷, K Carloni¹⁰, J Carpio^{33

34}, S Chattopadhyay⁴, N Chau⁵, Z Chen³⁵, D Chirkin⁴, S Choi^{36

37}, B A Clark²², A Coleman²⁰, P Coleman²⁸, G H Collin³⁸, A Connolly^{17

18}, J M Conrad³⁸, R Corley¹¹, D F Cowen^{39

40}, C De Clercq⁴¹, J J DeLaunay²⁵, D Delgado¹⁰, S Deng²⁸, A Desai⁴, P Desiati⁴, K D de Vries⁴¹, G de Wasseige⁴², T DeYoung¹², A Diaz³⁸, J C Díaz-Vélez⁴, P Dierichs²⁸, M Dittmer⁴³, A Domi⁴⁴, L Draper¹¹, H Dujmovic⁴, D Durnford⁴⁵, K Dutta²⁷, M A DuVernois⁴, T Ehrhardt²⁷, L Eidenschink¹⁵, A Eimer⁴⁴, P Eller¹⁵, E Ellinger⁴⁶, S El Mentawi²⁸, D Elsässer⁷, R Engel^{26

47}, H Erpenbeck⁴, W Esmail⁴³, J Evans²², P A Evenson⁸, K L Fan²², K Fang⁴, K Farrag⁴⁸, A R Fazely⁴⁹, A Fedynitch⁵⁰, N Feigl⁵¹, S Fiedlschuster⁴⁴, C Finley⁵², L Fischer², D Fox³⁹, A Franckowiak¹⁹, S Fukami², P Fürst²⁸, J Gallagher⁵³, E Ganster²⁸, A Garcia¹⁰, M Garcia⁸, G Garg⁴, E Genton^{10

42}, L Gerhardt⁵⁴, A Ghadimi²⁵, C Girard-Carillo²⁷, C Glaser²⁰, T Glüsenkamp²⁰, J G Gonzalez⁸, S Goswami^{33

34}, A Granados¹², D Grant⁵⁵, S J Gray²², S Griffin⁴, S Griswold²¹, K M Groth⁶, D Guevel⁴, C Günther²⁸, P Gutjahr⁷, C Ha⁵⁶, C Haack⁴⁴, A Hallgren²⁰, L Halve²⁸, F Halzen⁴, L Hamacher²⁸, H Hamdaoui³⁵, M Ha Minh¹⁵, M Handt²⁸, K Hanson⁴, J Hardin³⁸, A A Harnisch¹², P Hatch³⁰, A Haungs²⁶, J Häußler²⁸, K Helbing⁴⁶, J Hellrung¹⁹, J Hermannsgabner²⁸, L Heuermann²⁸, N Heyer²⁰, S Hickford⁴⁶, A Hidvegi⁵², C Hill⁴⁸, G C Hill³¹, R Hmaid⁴⁸, K D Hoffman²², S Hori⁴, K Hoshina⁴, M Hostert¹⁰, W Hou²⁶, T Huber²⁶, K Hultqvist⁵², M Hünnefeld⁴, R Hussain⁴, K Hymon^{7

50}, A Ishihara⁴⁸, W Iwakiri⁴⁸, M Jacquart⁴, S Jain⁴, O Janik⁴⁴, M Jansson³⁶, M Jeong¹¹, M Jin¹⁰, B J P Jones⁵⁷, N Kamp¹⁰, D Kang²⁶, W Kang³⁶, X Kang³², A Kappes⁴³, D Kappesser²⁷, L Kardum⁷, T Karg², M Karl¹⁵, A Karle⁴, A Katil⁴⁵, U Katz⁴⁴, M Kauer⁴, J L Kelley⁴, M Khanal¹¹, A Khatee Zathul⁴, A Kheirandish^{33

34}, J Kiryluk³⁵, S R Klein^{16

54}, Y Kobayashi⁴⁸, A Kochocki¹², R Koirala⁸, H Kolanoski⁵¹, T Kontrimas¹⁵, L Köpke²⁷, C Kopper⁴⁴, D J Koskinen⁶, P Koundal⁸, M Kowalski^{51

2}, T Kozynets⁶, N Krieger¹⁹, J Krishnamoorthi⁴, T Krishnan¹⁰, K Kruiswijk⁴², E Krupczak¹², A Kumar², E Kun¹⁹, N Kurahashi³², N Lad², C Lagunas Gualda¹⁵, M Lamoureux⁴², M J Larson²², F Lauber⁴⁶, J P Lazar⁴², K Leonard DeHolton⁴⁰, A Leszczyńska⁸, J Liao²⁹, M Lincetto¹⁹, Y T Liu⁴⁰, M Liubarska⁴⁵, C Love³², L Lu⁴, F Lucarelli⁵⁸, W Luszczak^{17

18}, Y Lyu^{16

54}, J Madsen⁴, E Magnus⁴¹, K B M Mahn¹², Y Makino⁴, E Manao¹⁵, S Mancina²³, A Mand⁴, W Marie Sainte⁴, I C Mariş⁵, S Marka⁵⁹, Z Marka⁵⁹, M Marsee²⁵, I Martinez-Soler¹⁰, R Maruyama⁶⁰, F Mayhew¹², F McNally⁶¹, J V Mead⁶, K Meagher⁴, S Mechbal², A Medina¹⁸, M Meier⁴⁸, Y Merckx⁴¹, L Merten¹⁹, J Mitchell⁴⁹, T Montaruli⁵⁸, R W Moore⁴⁵, Y Morii⁴⁸, R Morse⁴, M Moulai⁴, T Mukherjee²⁶, R Naab², M Nakos⁴, U Naumann⁴⁶, J Necker², A Negi⁵⁷, L Neste⁵², M Neumann⁴³, H Niederhausen¹², M U Nisa¹², K Noda⁴⁸, A Noell²⁸, A Novikov⁸, A Obertacke Pollmann⁴⁸, V O'Dell⁴, A Olivas²², R Orsoe¹⁵, J Osborn⁴, E O'Sullivan²⁰, V Palusova²⁷, H Pandya⁸, N Park³⁰, G K Parker⁵⁷, V Parrish¹², E N Paudel⁸, L Paul¹³, C Pérez de Los Heros²⁰, T Pernice², J Peterson⁴, A Pizzuto⁴, M Plum¹³, A Pontén²⁰, Y Popovych²⁷, M Prado Rodriguez⁴, B Pries¹², R Procter-Murphy²², G T Przybylski⁵⁴, L Pyras¹¹, C Raab⁴², J Rack-Helleis²⁷, N Rad², M Ravn²⁰, K Rawlins⁶², Z Rechav⁴, A Rehman⁸, E Resconi¹⁵, S Reusch², W Rhode⁷, B Riedel⁴, A Rifaie⁴⁶, E J Roberts³¹, S Robertson^{16

54}, S Rodan^{36

37}, M Rongen⁴⁴, A Rosted⁴⁸, C Rott^{11

36}, T Ruhe⁷, L Ruohan¹⁵, D Ryckbosch⁶³, I Safa⁴, J Saffer⁴⁷, D Salazar-Gallegos¹², P Sampathkumar²⁶, A Sandrock⁴⁶, M Santander²⁵, S Sarkar⁴⁵, S Sarkar⁶⁴, J Savelberg²⁸, P Savina⁴, P Schaile¹⁵, M Schaufel²⁸, H Schieler²⁶, S Schindler⁴⁴, L Schlickmann²⁷, B Schlüter⁴³, F Schlüter⁵, N Schmeisser⁴⁶, T Schmidt²², J Schneider⁴⁴, F G Schröder^{26

8}, L Schumacher⁴⁴, S Schwirn²⁸, S Sclafani²², D Seckel⁸, L Seen⁴, M Seikh²⁴, M Seo³⁶, S Seunarine⁶⁵, P Sevle Myhr⁴², R Shah³², S Shefali⁴⁷, N Shimizu⁴⁸, M Silva⁴, B Skrzypek¹⁶, B Smithers⁵⁷, R Snihur⁴, J Soedingrekso⁷, A Søgaard⁶, D Soldin¹¹, P Soldin²⁸, G Sommani¹⁹, C Spannfellner¹⁵, G M Spiczak⁶⁵, C Spiering², J Stachurska⁶³, M Stamatikos¹⁸, T Stanev⁸, T Stezelberger⁵⁴, T Stürwald⁴⁶, T Stuttard⁶, G W Sullivan²², I Taboada²⁹, S Ter-Antonyan⁴⁹, A Terliuk¹⁵, M Thiesmeyer⁴, W G Thompson¹⁰, J Thwaites⁴, S Tilav⁸, K Tollefson¹², C Tönnis³⁶, S Toscano⁵, D Tosi⁴, A Trettin², M A Unland Elorrieta⁴³, A K Upadhyay⁴, K Upshaw⁴⁹, A Vaidyanathan⁹, N Valtonen-Mattila²⁰, J Vandenbroucke⁴, N van Eijndhoven⁴¹, D Vannerom³⁸, J van Santen², J Vara⁴³, F Varsi⁴⁷, J Veitch-Michaelis⁴, M Venugopal²⁶, M Vereecken⁴², S Vergara Carrasco³, S Verpoest⁸, D Veske⁵⁹, A Vijai²², C Walck⁵², A Wang²⁹, C Weaver¹², P Weigel³⁸, A Weindl²⁶, J Weldert⁴⁰, A Y Wen¹⁰, C Wendt⁴, J Werthebach⁷, M Weyrauch²⁶, N Whitehorn¹², C H Wiebusch²⁸, D R Williams²⁵, L Witthaus⁷, M Wolf¹⁵, G Wrede⁴⁴, X W Xu⁴⁹, J P Yanez⁴⁵, E Yildizci⁴, S Yoshida⁴⁸, R Young²⁴, F Yu¹⁰, S Yu¹¹, T Yuan⁴, A Zegarelli¹⁹, S Zhang¹², Z Zhang³⁵, P Zhelnin¹⁰, P Zilberman⁴, M Zimmerman⁴; IceCube Collaboration

Affiliations

¹ Department of Physics, Loyola University Chicago, Chicago, Illinois 60660, USA.
² Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany.
³ Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
⁴ Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
⁵ Université Libre de Bruxelles, Science Faculty CP230, B-1050 Brussels, Belgium.
⁶ Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark.
⁷ Department of Physics, TU Dortmund University, D-44221 Dortmund, Germany.
⁸ Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA.
⁹ Department of Physics, Marquette University, Milwaukee, Wisconsin 53201, USA.
¹⁰ Department of Physics and Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, Massachusetts 02138, USA.
¹¹ Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA.
¹² Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
¹³ Physics Department, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701, USA.
¹⁴ Department of Physics and Astronomy, University of California, Irvine, California 92697, USA.
¹⁵ Physik-department, Technische Universität München, D-85748 Garching, Germany.
¹⁶ Department of Physics, University of California, Berkeley, California 94720, USA.
¹⁷ Department of Astronomy, Ohio State University, Columbus, Ohio 43210, USA.
¹⁸ Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210, USA.
¹⁹ Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
²⁰ Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
²¹ Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.
²² Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
²³ Dipartimento di Fisica e Astronomia Galileo Galilei, Università Degli Studi di Padova, I-35122 Padova PD, Italy.
²⁴ Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA.
²⁵ Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA.
²⁶ Karlsruhe Institute of Technology, Institute for Astroparticle Physics, D-76021 Karlsruhe, Germany.
²⁷ Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz, Germany.
²⁸ III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen, Germany.
²⁹ School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
³⁰ Department of Physics, Engineering Physics, and Astronomy, Queen's University, Kingston, Ontario K7L 3N6, Canada.
³¹ Department of Physics, University of Adelaide, Adelaide 5005, Australia.
³² Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, USA.
³³ Department of Physics and Astronomy, University of Nevada, Las Vegas, Nevada 89154, USA.
³⁴ Nevada Center for Astrophysics, University of Nevada, Las Vegas, Nevada 89154, USA.
³⁵ Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA.
³⁶ Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea.
³⁷ Institute of Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea.
³⁸ Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
³⁹ Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
⁴⁰ Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
⁴¹ Vrije Universiteit Brussel (VUB), Dienst ELEM, B-1050 Brussels, Belgium.
⁴² Centre for Cosmology, Particle Physics and Phenomenology - CP3, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
⁴³ Institut für Kernphysik, Universität Münster, D-48149 Münster, Germany.
⁴⁴ Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany.
⁴⁵ Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.
⁴⁶ Department of Physics, University of Wuppertal, D-42119 Wuppertal, Germany.
⁴⁷ Karlsruhe Institute of Technology, Institute of Experimental Particle Physics, D-76021 Karlsruhe, Germany.
⁴⁸ Department of Physics and The International Center for Hadron Astrophysics, Chiba University, Chiba 263-8522, Japan.
⁴⁹ Department of Physics, Southern University, Baton Rouge, Louisiana 70813, USA.
⁵⁰ Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan.
⁵¹ Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin, Germany.
⁵² Oskar Klein Centre and Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden.
⁵³ Department of Astronomy, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
⁵⁴ Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
⁵⁵ Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
⁵⁶ Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea.
⁵⁷ Department of Physics, University of Texas at Arlington, 502 Yates Street, Science Hall Room 108, Box 19059, Arlington, Texas 76019, USA.
⁵⁸ Département de physique nucléaire et corpusculaire, Université de Genève, CH-1211 Genève, Switzerland.
⁵⁹ Columbia Astrophysics and Nevis Laboratories, Columbia University, New York, New York 10027, USA.
⁶⁰ Department of Physics, Yale University, New Haven, Connecticut 06520, USA.
⁶¹ Department of Physics, Mercer University, Macon, Georgia 31207-0001, USA.
⁶² Department of Physics and Astronomy, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, Alaska 99508, USA.
⁶³ Department of Physics and Astronomy, University of Gent, B-9000 Gent, Belgium.
⁶⁴ Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
⁶⁵ Department of Physics, University of Wisconsin, River Falls, Wisconsin 54022, USA.

PMID: 40758031
DOI: 10.1103/PhysRevLett.135.031001

Search for Extremely-High-Energy Neutrinos and First Constraints on the Ultrahigh-Energy Cosmic-Ray Proton Fraction with IceCube

R Abbasi et al. Phys Rev Lett. 2025.

. 2025 Jul 18;135(3):031001.

doi: 10.1103/PhysRevLett.135.031001.

Authors

Affiliations

¹ Department of Physics, Loyola University Chicago, Chicago, Illinois 60660, USA.
² Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany.
³ Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand.
⁴ Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
⁵ Université Libre de Bruxelles, Science Faculty CP230, B-1050 Brussels, Belgium.
⁶ Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark.
⁷ Department of Physics, TU Dortmund University, D-44221 Dortmund, Germany.
⁸ Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA.
⁹ Department of Physics, Marquette University, Milwaukee, Wisconsin 53201, USA.
¹⁰ Department of Physics and Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, Massachusetts 02138, USA.
¹¹ Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112, USA.
¹² Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA.
¹³ Physics Department, South Dakota School of Mines and Technology, Rapid City, South Dakota 57701, USA.
¹⁴ Department of Physics and Astronomy, University of California, Irvine, California 92697, USA.
¹⁵ Physik-department, Technische Universität München, D-85748 Garching, Germany.
¹⁶ Department of Physics, University of California, Berkeley, California 94720, USA.
¹⁷ Department of Astronomy, Ohio State University, Columbus, Ohio 43210, USA.
¹⁸ Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210, USA.
¹⁹ Fakultät für Physik und Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
²⁰ Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
²¹ Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA.
²² Department of Physics, University of Maryland, College Park, Maryland 20742, USA.
²³ Dipartimento di Fisica e Astronomia Galileo Galilei, Università Degli Studi di Padova, I-35122 Padova PD, Italy.
²⁴ Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA.
²⁵ Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA.
²⁶ Karlsruhe Institute of Technology, Institute for Astroparticle Physics, D-76021 Karlsruhe, Germany.
²⁷ Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz, Germany.
²⁸ III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen, Germany.
²⁹ School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
³⁰ Department of Physics, Engineering Physics, and Astronomy, Queen's University, Kingston, Ontario K7L 3N6, Canada.
³¹ Department of Physics, University of Adelaide, Adelaide 5005, Australia.
³² Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, USA.
³³ Department of Physics and Astronomy, University of Nevada, Las Vegas, Nevada 89154, USA.
³⁴ Nevada Center for Astrophysics, University of Nevada, Las Vegas, Nevada 89154, USA.
³⁵ Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA.
³⁶ Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea.
³⁷ Institute of Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea.
³⁸ Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
³⁹ Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
⁴⁰ Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
⁴¹ Vrije Universiteit Brussel (VUB), Dienst ELEM, B-1050 Brussels, Belgium.
⁴² Centre for Cosmology, Particle Physics and Phenomenology - CP3, Université catholique de Louvain, Louvain-la-Neuve, Belgium.
⁴³ Institut für Kernphysik, Universität Münster, D-48149 Münster, Germany.
⁴⁴ Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany.
⁴⁵ Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada.
⁴⁶ Department of Physics, University of Wuppertal, D-42119 Wuppertal, Germany.
⁴⁷ Karlsruhe Institute of Technology, Institute of Experimental Particle Physics, D-76021 Karlsruhe, Germany.
⁴⁸ Department of Physics and The International Center for Hadron Astrophysics, Chiba University, Chiba 263-8522, Japan.
⁴⁹ Department of Physics, Southern University, Baton Rouge, Louisiana 70813, USA.
⁵⁰ Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan.
⁵¹ Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin, Germany.
⁵² Oskar Klein Centre and Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden.
⁵³ Department of Astronomy, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
⁵⁴ Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
⁵⁵ Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada.
⁵⁶ Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea.
⁵⁷ Department of Physics, University of Texas at Arlington, 502 Yates Street, Science Hall Room 108, Box 19059, Arlington, Texas 76019, USA.
⁵⁸ Département de physique nucléaire et corpusculaire, Université de Genève, CH-1211 Genève, Switzerland.
⁵⁹ Columbia Astrophysics and Nevis Laboratories, Columbia University, New York, New York 10027, USA.
⁶⁰ Department of Physics, Yale University, New Haven, Connecticut 06520, USA.
⁶¹ Department of Physics, Mercer University, Macon, Georgia 31207-0001, USA.
⁶² Department of Physics and Astronomy, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, Alaska 99508, USA.
⁶³ Department of Physics and Astronomy, University of Gent, B-9000 Gent, Belgium.
⁶⁴ Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom.
⁶⁵ Department of Physics, University of Wisconsin, River Falls, Wisconsin 54022, USA.

PMID: 40758031
DOI: 10.1103/PhysRevLett.135.031001

Abstract

We present a search for the diffuse extremely-high-energy neutrino flux using 12.6 years of IceCube data. The nonobservation of neutrinos with energies well above 10 PeV constrains the all-flavor neutrino flux at 10^{18} eV to a level of E^{2}Φ_{ν_{e}+ν_{μ}+ν_{τ}}≃10^{-8} GeV cm^{-2} s^{-1} sr^{-1}, the most stringent limit to date. Using these data, we constrain the proton fraction of ultrahigh-energy cosmic rays (UHECRs) above ≃30 EeV to be ≲70% (at 90% CL) if the cosmological evolution of the sources is comparable to or stronger than the star formation rate. This is the first result to disfavor the "proton-only" hypothesis for UHECR in this evolution regime using neutrino data. This result complements direct air-shower measurements by being insensitive to uncertainties associated with hadronic interaction models. We also evaluate the tension between IceCube's nonobservation and the ∼200 PeV KM3NeT neutrino candidate (KM3-230213A), finding it to be ∼2.9σ based on a joint-livetime fit between neutrino datasets.

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Search for Extremely-High-Energy Neutrinos and First Constraints on the Ultrahigh-Energy Cosmic-Ray Proton Fraction with IceCube

Affiliations

Search for Extremely-High-Energy Neutrinos and First Constraints on the Ultrahigh-Energy Cosmic-Ray Proton Fraction with IceCube

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Affiliations

Abstract

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