Eur. Phys. J. C (2019) 79: 234
https://doi.org/10.1140/epjc/s10052-019-6680-0

Regular Article - Experimental Physics

Search for steady point-like sources in the astrophysical muon neutrino flux with 8 years of IceCube data

¹ III. Physikalisches Institut, RWTH Aachen University, 52056, Aachen, Germany
² Department of Physics, University of Adelaide, Adelaide, 5005, Australia
³ Department of Physics and Astronomy, University of Alaska Anchorage, 3211 Providence Dr., Anchorage, AK, 99508, USA
⁴ Department of Physics, University of Texas at Arlington, 502 Yates St., Science Hall Rm 108, Box 19059, Arlington, TX, 76019, USA
⁵ CTSPS, Clark-Atlanta University, Atlanta, GA, 30314, USA
⁶ School of Physics and Center for Relativistic Astrophysics, Georgia Institute of Technology, Atlanta, GA, 30332, USA
⁷ Department of Physics, Southern University, Baton Rouge, LA, 70813, USA
⁸ Department of Physics, University of California, Berkeley, CA, 94720, USA
⁹ Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
¹⁰ Institut für Physik, Humboldt-Universität zu Berlin, 12489, Berlin, Germany
¹¹ Fakultät für Physik & Astronomie, Ruhr-Universität Bochum, 44780, Bochum, Germany
¹² Science Faculty CP230, Université Libre de Bruxelles, 1050, Brussels, Belgium
¹³ Dienst ELEM, Vrije Universiteit Brussel (VUB), 1050, Brussels, Belgium
¹⁴ Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
¹⁵ Department of Physics and Institute for Global Prominent Research, Chiba University, Chiba, 263-8522, Japan
¹⁶ Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
¹⁷ Department of Physics, University of Maryland, College Park, MD, 20742, USA
¹⁸ Department of Physics and Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH, 43210, USA
¹⁹ Department of Astronomy, Ohio State University, Columbus, OH, 43210, USA
²⁰ Niels Bohr Institute, University of Copenhagen, 2100, Copenhagen, Denmark
²¹ Department of Physics, TU Dortmund University, 44221, Dortmund, Germany
²² Department of Physics and Astronomy, Michigan State University, East Lansing, MI, 48824, USA
²³ Department of Physics, University of Alberta, Edmonton, Alberta, T6G 2E1, Canada
²⁴ Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91058, Erlangen, Germany
²⁵ Département de Physique Nucléaire et Corpusculaire, Université de Genève, 1211, Geneva, Switzerland
²⁶ Department of Physics and Astronomy, University of Gent, 9000, Gent, Belgium
²⁷ Department of Physics and Astronomy, University of California, Irvine, CA, 92697, USA
²⁸ Department of Physics and Astronomy, University of Kansas, Lawrence, KS, 66045, USA
²⁹ SNOLAB, 1039 Regional Road 24, Creighton Mine 9, Lively, ON, P3Y 1N2, Canada
³⁰ Department of Physics and Astronomy, UCLA, Los Angeles, CA, 90095, USA
³¹ Department of Astronomy, University of Wisconsin, Madison, WI, 53706, USA
³² Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin, Madison, WI, 53706, USA
³³ Institute of Physics, University of Mainz, Staudinger Weg 7, 55099, Mainz, Germany
³⁴ Department of Physics, Marquette University, Milwaukee, WI, 53201, USA
³⁵ Physik-Department, Technische Universität München, 85748, Garching, Germany
³⁶ Institut für Kernphysik, Westfälische Wilhelms-Universität Münster, 48149, Münster, Germany
³⁷ Department of Physics and Astronomy, Bartol Research Institute, University of Delaware, Newark, DE, 19716, USA
³⁸ Department of Physics, Yale University, New Haven, CT, 06520, USA
³⁹ Department of Physics, University of Oxford, 1 Keble Road, Oxford, OX1 3NP, UK
⁴⁰ Department of Physics, Drexel University, 3141 Chestnut Street, Philadelphia, PA, 19104, USA
⁴¹ Physics Department, South Dakota School of Mines and Technology, Rapid City, SD, 57701, USA
⁴² Department of Physics, University of Wisconsin, River Falls, WI, 54022, USA
⁴³ Department of Physics and Astronomy, University of Rochester, Rochester, NY, 14627, USA
⁴⁴ Department of Physics, Oskar Klein Centre, Stockholm University, 10691, Stockholm, Sweden
⁴⁵ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY, 11794-3800, USA
⁴⁶ Department of Physics, Sungkyunkwan University, Suwon, 440-746, Korea
⁴⁷ Department of Physics and Astronomy, University of Alabama, Tuscaloosa, AL, 35487, USA
⁴⁸ Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA, 16802, USA
⁴⁹ Department of Physics, Pennsylvania State University, University Park, PA, 16802, USA
⁵⁰ Department of Physics and Astronomy, Uppsala University, Box 516, 75120, Uppsala, Sweden
⁵¹ Department of Physics, University of Wuppertal, 42119, Wuppertal, Germany
⁵² DESY, 15738, Zeuthen, Germany
⁵³ https://icecube.wisc.edu/

^* e-mail: analysis@icecube.wisc.edu

Received: 19 November 2018
Accepted: 13 February 2019
Published online: 13 March 2019

Abstract

The IceCube Collaboration has observed a high-energy astrophysical neutrino flux and recently found evidence for neutrino emission from the blazar TXS 0506056. These results open a new window into the high-energy universe. However, the source or sources of most of the observed flux of astrophysical neutrinos remains uncertain. Here, a search for steady point-like neutrino sources is performed using an unbinned likelihood analysis. The method searches for a spatial accumulation of muon-neutrino events using the very high-statistics sample of about 497,000 neutrinos recorded by IceCube between 2009 and 2017. The median angular resolution is at 1 TeV and improves to for neutrinos with an energy of 1 PeV. Compared to previous analyses, this search is optimized for point-like neutrino emission with the same flux-characteristics as the observed astrophysical muon-neutrino flux and introduces an improved event-reconstruction and parametrization of the background. The result is an improvement in sensitivity to the muon-neutrino flux compared to the previous analysis of assuming an spectrum. The sensitivity on the muon-neutrino flux is at a level of . No new evidence for neutrino sources is found in a full sky scan and in an a priori candidate source list that is motivated by gamma-ray observations. Furthermore, no significant excesses above background are found from populations of sub-threshold sources. The implications of the non-observation for potential source classes are discussed.