High-energy fluxes of atmospheric neutrinos

TL;DR

This paper provides detailed calculations of high-energy atmospheric neutrino spectra using various hadronic models and cosmic ray parameterizations, comparing results with IceCube data to understand background neutrino fluxes and potential astrophysical signals.

Contribution

It offers new high-energy neutrino flux calculations based on multiple models and cosmic ray spectra, aligning them with experimental measurements and exploring implications for astrophysical neutrino detection.

Findings

Prompt neutrino flux predictions are consistent with IceCube limits.

The neutrino flavor ratio decreases with energy, indicating possible early charm decay contributions.

Diffuse astrophysical neutrino flux may explain flavor ratio behavior below 10 TeV.

Abstract

High-energy neutrinos from decays of mesons, produced in collisions of cosmic ray particles with air nuclei, form unavoidable background for detection of astrophysical neutrinos. More precise calculations of the high-energy neutrino spectrum are required since measurements in the IceCube experiment reach the intriguing energy region where a contribution of the prompt neutrinos and/or astrophysical ones should be discovered. Basing on the referent hadronic models QGSJET II-03, SIBYLL 2.1, we calculate high-energy spectra, both of the muon and electron atmospheric neutrinos, averaged over zenith-angles. The computation is made using three parameterizations of cosmic ray spectra which include the knee region. All calculations are compared with the atmospheric neutrino measurements by Frejus and IceCube. The prompt neutrino flux predictions obtained with thequark-gluon string model (QGSM) for the charm production by Kaidalov & Piskunova do not contradict to the IceCube measurements and upper limit on the astrophysical muon neutrino flux. Neutrino flavor ratio, $\phi_{\nu_ mu}/\phi_{\nu_e}$, extracted from IceCube data decreases in the energy range $0.1 - 5$ TeV energy contrary to that one might expect from the conventional neutrino flux. Presumable reasons of such behavior are: i) early arising contribution from decays of charmed particle, differing from predictions of present models, ii) revealed diffuse flux of astrophysical electron neutrinos. The likely diffuse flux of astrophysical neutrinos related to the PeV neutrino events, detected in the IceCube experiment, leads to a decrease of the flavor ratio at the energy below 10 TeV, that is in qualitative agreement with a rough approximation for theflavor ratio obtained from the IceCube data.