Improved Characterization of the Astrophysical Muon–neutrino Flux with 9.5 Years of IceCube Data

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 ϕ @ 100 TeV ν μ + ν ¯ μ = 1.44 − 0.26 + 0.25 × 10 − 18 GeV − 1 cm − 2 s − 1 sr − 1 and a spectral index γ SPL = 2.37 − 0.09 + 0.09 , 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.

The ultra-high-energy neutrino-nucleon cross section: measurement forecasts for an era of cosmic EeV-neutrino discovery

“…We have not discovered a flux of UHE neutrinos yet, so we are forced to consider different possibilities. In our forecasts, we assume a wide variety of UHE neutrino flux predictions that span the breadth available in the literature, from pessimistic to optimistic [29,[54][55][56][57][58][59][60][61][62]. We model in detail the flavor content of neutrinos and antineutrinos in the flux, and keep track of it throughout.…”

“…5. Benchmark UHE neutrino flux models used in our analysis [29,[54][55][56][57][58][59][60][61][62]. Highlighted models 2, 4, 6, and 7 receive special attention in the main text, but results for all models are shown in Tables I and II, and in Appendix A.…”

“…In this plot, we showcase 10-year forecasts for three attractive flux scenarios that may afford the most precise cross-section measurements [54,55] (models 2, 4, and 7 below). Table II shows results for many more flux models [29,[54][55][56][57][58][59][60][61][62] (Section IV).…”

“…In this plot, we showcase 10-year forecasts for three attractive flux scenarios that may afford the most precise cross-section measurements [54,55] (models 2, 4, and 7 below). Table II shows results for many more flux models [29,[54][55][56][57][58][59][60][61][62] (Section IV). The precision of cross-section measurements that we report accounts for the significant uncertainty on the flux normalization (Section VII), and detector resolution (Section VI).…”

“…in the size of their flux and a wide variety of shapes of their energy spectrum from the literature [29,[54][55][56][57][58][59][60][61][62].…”