IceCube high-energy starting event sample: Description and flux characterization with 7.5 years of data
R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, M. Ahrens, Cyril Martin Alispach, A. A. Alves, N. M. Amin, K. Andeen, T. Anderson, I. Ansseau, G. Anton, C. Argüelles, Spencer Axani, X. Bai, Aswathi Balagopal, Anastasia Maria Barbano, S. W. Barwick, Benjamin Bastian, Vedant Basu, V. Baum, S. Baur, R. Bay, J. J. Beatty, K. Becker, J. Becker Tjus, Chiara Bellenghi, S. BenZvi, D. Berley, E. Bernardini, D. Besson, G. Binder, D. Bindig, E. Blaufuss, Summer Blot, S. Böser, O. Botner, J. Böttcher, Etienne Bourbeau, J. Bourbeau, Federica Bradascio, J. Braun, S. Bron, Jannes Brostean-Kaiser, A. Burgman, Raffaela Busse, Michael Campana, C. Chen, D. Chirkin, S. Choi, Brian Clark, K. Clark, Lew Classen, Alan Coleman, G. H. Collin, J. M. Conrad, Paul Coppin, Pablo Correa, D. F. Cowen, R. Cross, Pranav Dave, C. De Clercq, James DeLaunay, H.-P. Dembinski, Kunal Deoskar, S. De Ridder, Abhishek Desai, P. Desiati, K. D. de Vries, G. de Wasseige, M. de With, T. DeYoung, Sukeerthi Dharani, A. Diaz, J. C. Díaz–Vélez, Hrvoje Dujmović, M. Dunkman, M. A. DuVernois, Emily Dvorak, Thomas Ehrhardt, P. Eller, R. Engel, John Evans, P. A. Evenson, S. Fahey, A. R. Fazely, Sebastian Fiedlschuster, Aaron Fienberg, K. Filimonov, C. Finley, Leander Fischer, D. B. Fox, A. Franckowiak, Edward Friedman, Alexander Fritz, Philipp Fürst, T. K. Gaisser, J. S. Gallagher, Erik Ganster
Abstract
The IceCube Neutrino Observatory has established the existence of a high-energy all-sky neutrino flux of astrophysical origin. This discovery was made using events interacting within a fiducial region of the detector surrounded by an active veto and with reconstructed energy above 60 TeV, commonly known as the high-energy starting event sample (HESE). We revisit the analysis of the HESE sample with an additional 4.5 years of data, newer glacial ice models, and improved systematics treatment. This paper describes the sample in detail, reports on the latest astrophysical neutrino flux measurements, and presents a source search for astrophysical neutrinos. We give the compatibility of these observations with specific isotropic flux models proposed in the literature as well as generic power-law-like scenarios. Assuming ${\ensuremath{\nu}}_{e}:{\ensuremath{\nu}}_{\ensuremath{\mu}}:{\ensuremath{\nu}}_{\ensuremath{\tau}}=1:1:1$, and an equal flux of neutrinos and antineutrinos, we find that the astrophysical neutrino spectrum is compatible with an unbroken power law, with a preferred spectral index of ${2.87}_{\ensuremath{-}0.19}^{+0.20}$ for the 68% confidence interval.