Improved Characterization of the Astrophysical Muon–neutrino Flux with 9.5 Years of IceCube Data
Rasha Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, M. Ahrens, Jean-Marco Alameddine, Cyril Martin Alispach, A. A. Alves, N. M. Amin, K. Andeen, T. Anderson, G. Anton, C. Argüelles, Yosuke Ashida, Spencer Axani, X. Bai, Aswathi Balagopal, Anastasia Maria Barbano, S. W. Barwick, Benjamin Bastian, Vedant Basu, S. Baur, R. Bay, J. J. Beatty, Karl H. Becker, J. Becker Tjus, Chiara Bellenghi, S. BenZvi, D. Berley, E. Bernardini, D. Besson, G. Binder, D. Bindig, E. Blaufuss, Summer Blot, Matthias Boddenberg, Federico Bontempo, Jürgen Borowka, S. Böser, O. Botner, J. Böttcher, Etienne Bourbeau, Federica Bradascio, J. Braun, Bennett Brinson, S. Bron, Jannes Brostean-Kaiser, Sally-Ann Browne, A. Burgman, Ryan T. Burley, Raffaela Busse, Michael Campana, Erin Carnie-Bronca, Kunal Deoskar, Z. Chen, D. Chirkin, K. Choi, Brian Clark, K. Clark, Lew Classen, Alan Coleman, G. H. Collin, J. M. Conrad, Paul Coppin, Pablo Correa, D. F. Cowen, R. Cross, Christian Dappen, Pranav Dave, C. De Clercq, James DeLaunay, Diyaselis Delgado, H.-P. Dembinski, Kunal Deoskar, Abhishek Desai, P. Desiati, K. D. de Vries, G. de Wasseige, M. de With, T. DeYoung, A. Diaz, J. C. Díaz–Vélez, Markus Dittmer, Hrvoje Dujmović, M. Dunkman, M. A. DuVernois, Emily Dvorak, Thomas Ehrhardt, P. Eller, R. Engel, Hannah Erpenbeck, John Evans, P. A. Evenson, Kwok Lung Fan, A. R. Fazely, Nora Feigl, Sebastian Fiedlschuster, Aaron Fienberg, K. Filimonov
Abstract
Abstract We present a measurement of the high-energy astrophysical muon–neutrino flux with the IceCube Neutrino Observatory. The measurement uses a high-purity selection of 650k neutrino-induced muon tracks from the northern celestial hemisphere, corresponding to 9.5 yr of experimental data. With respect to previous publications, the measurement is improved by the increased size of the event sample and the extended model testing beyond simple power-law hypotheses. An updated treatment of systematic uncertainties and atmospheric background fluxes has been implemented based on recent models. The best-fit single power-law parameterization for the astrophysical energy spectrum results in a normalization of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msubsup> <mml:mrow> <mml:mi>ϕ</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>@</mml:mo> <mml:mn>100</mml:mn> <mml:mi>TeV</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>μ</mml:mi> </mml:mrow> </mml:msub> <mml:mo>+</mml:mo> <mml:msub> <mml:mrow> <mml:mover accent="true"> <mml:mrow> <mml:mi>ν</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>¯</mml:mo> </mml:mrow> </mml:mover> </mml:mrow> <mml:mrow> <mml:mi>μ</mml:mi> </mml:mrow> </mml:msub> </mml:mrow> </mml:msubsup> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>1.44</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.26</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.25</mml:mn> </mml:mrow> </mml:msubsup> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>18</mml:mn> </mml:mrow> </mml:msup> <mml:mspace width="0.25em"/> <mml:msup> <mml:mrow> <mml:mi>GeV</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:msup> <mml:mrow> <mml:mi>cm</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>2</mml:mn> </mml:mrow> </mml:msup> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> <mml:msup> <mml:mrow> <mml:mi>sr</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:math> and a spectral index <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>γ</mml:mi> </mml:mrow> <mml:mrow> <mml:mi>SPL</mml:mi> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:msubsup> <mml:mrow> <mml:mn>2.37</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> <mml:mrow> <mml:mo>+</mml:mo> <mml:mn>0.09</mml:mn> </mml:mrow> </mml:msubsup> </mml:math> , constrained in the energy range from 15 TeV to 5 PeV. The model tests include a single power law with a spectral cutoff at high energies, a log-parabola model, several source-class-specific flux predictions from the literature, and a model-independent spectral unfolding. The data are consistent with a single power-law hypothesis, however, spectra with softening above one PeV are statistically more favorable at a two-sigma level.