Current constraints from cosmogenic neutrinos on the fraction of protons in UHECRs

Abstract

Cosmogenic neutrinos are created when ultra-high-energy cosmic rays (UHECRs) interact with extragalactic photon backgrounds. In general, the expected flux of these cosmogenic neutrinos depends on multiple parameters, describing the sources and propagation of UHECRs. In our recent paper (van Vliet et al. 2019), we show that a `sweet spot` occurs at a neutrino energy of $E_{\nu }\sim 1$ EeV. At that energy the flux mainly depends on two parameters, the source evolution and the fraction of protons in UHECRs at Earth for $E_p\gtrsim 30$ EeV. Therefore, with current upper limits on the cosmogenic neutrino flux at $E_{\nu }\sim 1$ EeV and assuming a certain source class, a constraint on the composition of UHECRs can be obtained. This constraint is independent of hadronic interaction models and indicates that the combination of a large proton fraction and a strong source evolution is disfavored. Upcoming neutrino experiments will be able to constrain the fraction of protons in UHECRs even further, and for any realistic model for the evolution of UHECR sources.

Presented at the 36th International Cosmic Ray Conference (ICRC 2019)

References in corpus (8)

• The Giant Radio Array for Neutrino Detection (GRAND): Science and Design
• Cosmogenic Neutrinos: parameter space and detectabilty from PeV to ZeV
• A new view on Auger data and cosmogenic neutrinos in light of different nuclear disintegration and air-shower models
• Determining the fraction of cosmic-ray protons at ultra-high energies with cosmogenic neutrinos
• Targeting ultra-high energy neutrinos with the ARIANNA experiment
• Progress towards characterizing ultrahigh energy cosmic ray sources
• Astrophysics Uniquely Enabled by Observations of High-Energy Cosmic Neutrinos
• Predictions for the flux of high-energy cosmogenic neutrinos and the influence of the extragalactic magnetic field