학술논문
Characteristics of the Diffuse Astrophysical Electron and Tau Neutrino Flux with Six Years of IceCube High Energy Cascade Data
Document Type
article
Author
Aartsen, MG; Ackermann, M; Adams, J; Aguilar, JA; Ahlers, M; Ahrens, M; Alispach, C; Andeen, K; Anderson, T; Ansseau, I; Anton, G; Argüelles, C; Auffenberg, J; Axani, S; Backes, P; Bagherpour, H; Bai, X; V., A Balagopal; Barbano, A; Barwick, SW; Bastian, B; Baum, V; Baur, S; Bay, R; Beatty, JJ; Becker, K-H; Tjus, J Becker; BenZvi, S; Berley, D; Bernardini, E; Besson, DZ; Binder, G; Bindig, D; Blaufuss, E; Blot, S; Bohm, C; Böser, S; Botner, O; Böttcher, J; Bourbeau, E; Bourbeau, J; Bradascio, F; Braun, J; Bron, S; Brostean-Kaiser, J; Burgman, A; Buscher, J; Busse, RS; Carver, T; Chen, C; Cheung, E; Chirkin, D; Choi, S; Clark, K; Classen, L; Coleman, A; Collin, GH; Conrad, JM; Coppin, P; Correa, P; Cowen, DF; Cross, R; Dave, P; De Clercq, C; DeLaunay, JJ; Dembinski, H; Deoskar, K; De Ridder, S; Desiati, P; de Vries, KD; de Wasseige, G; de With, M; DeYoung, T; Diaz, A; Díaz-Vélez, JC; Dujmovic, H; Dunkman, M; Dvorak, E; Eberhardt, B; Ehrhardt, T; Eller, P; Engel, R; Evenson, PA; Fahey, S; Fazely, AR; Felde, J; Filimonov, K; Finley, C; Fox, D; Franckowiak, A; Friedman, E; Fritz, A; Gaisser, TK; Gallagher, J; Ganster, E; Garrappa, S; Gerhardt, L; Ghorbani, K; Glauch, T; Glüsenkamp, T
Source
Physical Review Letters. 125(12)
Subject
Language
Abstract
We report on the first measurement of the astrophysical neutrino flux using particle showers (cascades) in IceCube data from 2010-2015. Assuming standard oscillations, the astrophysical neutrinos in this dedicated cascade sample are dominated (∼90%) by electron and tau flavors. The flux, observed in the sensitive energy range from 16 TeV to 2.6 PeV, is consistent with a single power-law model as expected from Fermi-type acceleration of high energy particles at astrophysical sources. We find the flux spectral index to be γ=2.53±0.07 and a flux normalization for each neutrino flavor of ϕ_{astro}=1.66_{-0.27}^{+0.25} at E_{0}=100 TeV, in agreement with IceCube's complementary muon neutrino results and with all-neutrino flavor fit results. In the measured energy range we reject spectral indices γ≤2.28 at ≥3σ significance level. Because of high neutrino energy resolution and low atmospheric neutrino backgrounds, this analysis provides the most detailed characterization of the neutrino flux at energies below ∼100 TeV compared to previous IceCube results. Results from fits assuming more complex neutrino flux models suggest a flux softening at high energies and a flux hardening at low energies (p value ≥0.06). The sizable and smooth flux measured below ∼100 TeV remains a puzzle. In order to not violate the isotropic diffuse gamma-ray background as measured by the Fermi Large Area Telescope, it suggests the existence of astrophysical neutrino sources characterized by dense environments which are opaque to gamma rays.