Probing the PeV region in the astrophysical neutrino spectrum using from the Southern sky
R. Abbasi17, M. Ackermann65, J. Adams18, S. K. Agarwalla40,*, J. A. Aguilar11, M. Ahlers22, J. M. Alameddine23, N. M. Amin44, K. Andeen42 et al. (IceCube Collaboration)
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Yoshida16, R. Young36, F. Yu14, S. Yu53, T. Yuan40, A. Zegarelli10, S. Zhang24, Z. Zhang56, P. Zhelnin14, P. Zilberman40, and M. Zimmerman40 (IceCube Collaboration)
- 1III. Physikalisches Institut, RWTH Aachen University, D-52056 Aachen, Germany
- 2Department of Physics, University of Adelaide, Adelaide, 5005, Australia
- 3Department of Physics and Astronomy, University of Alaska Anchorage, 3211 Providence Drive, Anchorage, Alaska 99508, USA
- 4Department of Physics, University of Texas at Arlington, 502 Yates Street, Science Hall Room 108, Box 19059, Arlington, Texas 76019, USA
- 5School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
- 6Department of Physics, Southern University, Baton Rouge, Louisiana 70813, USA
- 7Department of Physics, University of California, Berkeley, California 94720, USA
- 8Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
- 9Institut für Physik, Humboldt-Universität zu Berlin, D-12489 Berlin, Germany
- 10Fakultät für Physik and Astronomie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
- 11Université Libre de Bruxelles, Science Faculty CP230, B-1050 Brussels, Belgium
- 12Vrije Universiteit Brussel (VUB), Dienst ELEM, B-1050 Brussels, Belgium
- 13Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
- 14Department of Physics and Laboratory for Particle Physics and Cosmology, Harvard University, Cambridge, Massachusetts 02138, USA
- 15Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
- 16Department of Physics and The International Center for Hadron Astrophysics, Chiba University, Chiba 263-8522, Japan
- 17Department of Physics, Loyola University Chicago, Chicago, Illinois 60660, USA
- 18Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
- 19Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- 20Department of Astronomy, Ohio State University, Columbus, Ohio 43210, USA
- 21Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, Ohio 43210, USA
- 22Niels Bohr Institute, University of Copenhagen, DK-2100 Copenhagen, Denmark
- 23Department of Physics, TU Dortmund University, D-44221 Dortmund, Germany
- 24Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
- 25Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1, Canada
- 26Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, D-91058 Erlangen, Germany
- 27Physik-department, Technische Universität München, D-85748 Garching, Germany
- 28Département de physique nucléaire et corpusculaire, Université de Genève, CH-1211 Genève, Switzerland
- 29Department of Physics and Astronomy, University of Gent, B-9000 Gent, Belgium
- 30Department of Physics and Astronomy, University of California, Irvine, California 92697, USA
- 31Karlsruhe Institute of Technology, Institute for Astroparticle Physics, D-76021 Karlsruhe, Germany
- 32Karlsruhe Institute of Technology, Institute of Experimental Particle Physics, D-76021 Karlsruhe, Germany
- 33Department of Physics, Engineering Physics, and Astronomy, Queen’s University, Kingston, Ontario K7L 3N6, Canada
- 34Department of Physics and Astronomy, University of Nevada, Las Vegas, Nevada 89154, USA
- 35Nevada Center for Astrophysics, University of Nevada, Las Vegas, Nevada 89154, USA
- 36Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045, USA
- 37Centre for Cosmology, Particle Physics and Phenomenology—CP3, Université catholique de Louvain, Louvain-la-Neuve, Belgium
- 38Department of Physics, Mercer University, Macon, Georgia 31207-0001, USA
- 39Department of Astronomy, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA
- 40Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin–Madison, Madison, Wisconsin 53706, USA
- 41Institute of Physics, University of Mainz, Staudinger Weg 7, D-55099 Mainz, Germany
- 42Department of Physics, Marquette University, Milwaukee, Wisconsin 53201, USA
- 43Institut für Kernphysik, Universität Münster, D-48149 Münster, Germany
- 44Bartol Research Institute and Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716, USA
- 45Department of Physics, Yale University, New Haven, Connecticut 06520, USA
- 46Columbia Astrophysics and Nevis Laboratories, Columbia University, New York, New York 10027, USA
- 47Department of Physics, University of Oxford, Parks Road, Oxford, England OX1 3PU, United Kingdom
- 48Dipartimento di Fisica e Astronomia Galileo Galilei, Università Degli Studi di Padova, I-35122 Padova PD, Italy
- 49Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, USA
- 50Physics Department, South Dakota School of Mines and Technology, Rapid City, Sourth Dakota 57701, USA
- 51Department of Physics, University of Wisconsin, River Falls, Wisconsin 54022, USA
- 52Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627, USA
- 53Department of Physics and Astronomy, University of Utah, Salt Lake City, Urah 84112, USA
- 54Department of Physics, Chung-Ang University, Seoul 06974, Republic of Korea
- 55Oskar Klein Centre and Department of Physics, Stockholm University, SE-10691 Stockholm, Sweden
- 56Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794-3800, USA
- 57Department of Physics, Sungkyunkwan University, Suwon 16419, Republic of Korea
- 58Institute of Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea
- 59Institute of Physics, Academia Sinica, Taipei, 11529, Taiwan
- 60Department of Physics and Astronomy, University of Alabama, Tuscaloosa, Alabama 35487, USA
- 61Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- 62Department of Physics, Pennsylvania State University, University Park, Pennsylvania 16802, USA
- 63Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden
- 64Department of Physics, University of Wuppertal, D-42119 Wuppertal, Germany
- 65Deutsches Elektronen-Synchrotron DESY, Platanenallee 6, D-15738 Zeuthen, Germany
- *Also at Institute of Physics, Sachivalaya Marg, Sainik School Post, Bhubaneswar 751005, India.
- †Also at Department of Space, Earth and Environment, Chalmers University of Technology, 412 96 Gothenburg, Sweden.
- ‡Also at Earthquake Research Institute, University of Tokyo, Bunkyo, Tokyo 113-0032, Japan.
Phys. Rev. D 112, 012022 – Published 25 July, 2025
DOI: https://doi.org/10.1103/2hnq-1fsx
Abstract
IceCube has observed a diffuse astrophysical neutrino flux over the energy region from a few TeV to a few PeV. At PeV energies, the spectral shape is not yet well measured due to the low statistics of the data. This analysis probes the gap between 1 and 10 PeV by using high-energy downgoing muon neutrinos. To reject the large atmospheric muon background, two complementary techniques are combined. The first technique selects events with high stochasticity to reject atmospheric muon bundles whose stochastic energy losses are smoothed due to high muon multiplicity. The second technique vetoes atmospheric muons with the IceTop surface array. Using 9 yrs of data, we found two neutrino candidate events in the signal region, consistent with expectation from background, each with relatively high signal probabilities. A joint maximum likelihood estimation is performed using this sample and an independent 9.5-yr sample of tracks to measure the neutrino spectrum. A likelihood ratio test is done to compare the single power-law (SPL) vs hypothesis; the model is not significantly better than the SPL. High-energy astrophysical objects from four source catalogs are also checked around the direction of the two events. No significant coincidence was found.