Constraints on the origin of the ultra-high energy cosmic-rays using cosmic diffuse neutrino flux limits: An analytical approach

TL;DR

This paper develops an analytical method to constrain the properties of ultra-high energy cosmic-ray sources using diffuse neutrino flux limits, revealing that current and future neutrino observations can significantly restrict source evolution scenarios.

Contribution

It introduces a semi-analytic formula linking neutrino flux limits to cosmic-ray source characteristics in a model-independent manner.

Findings

IceCube neutrino limits constrain strongly evolving sources.

Future detectors can further restrict source evolution models.

Analytical approach simplifies constraints on cosmic-ray origins.

Abstract

Astrophysical neutrinos are expected to be produced in the interactions of ultra-high energy cosmic-rays with surrounding photons. The fluxes of the astrophysical neutrinos are highly dependent on the characteristics of the cosmic-ray sources, such as their cosmological distributions. We study possible constraints on the properties of cosmic-ray sources in a model-independent way using experimentally obtained diffuse neutrino flux above 100 PeV. The semi-analytic formula is derived to estimate the cosmogenic neutrino fluxes as functions of source evolution parameter and source extension in redshift. The obtained formula converts the upper-limits on the neutrino fluxes into the constraints on the cosmic-ray sources. It is found that the recently obtained upper-limit on the cosmogenic neutrinos by IceCube constrains the scenarios with strongly evolving ultra-high energy cosmic-ray sources, and the future limits from an 1 km^3 scale detector are able to further constrain the ultra-high energy cosmic-rays sources with evolutions comparable to the cosmic star formation rate.