Gamma-Ray Constraints on Maximum Cosmogenic Neutrino Fluxes and UHECR Source Evolution Models

TL;DR

This paper investigates the maximum expected cosmogenic neutrino fluxes based on UHECR source models and gamma-ray background constraints, highlighting detectability prospects with IceCube and ARA, and evaluating source evolution scenarios.

Contribution

It provides the first comprehensive analysis of cosmogenic neutrino flux limits within the dip model considering recent gamma-ray background data and source evolution models.

Findings

Largest fluxes detectable by IceCube in 10 years

Fluxes could be 2-3 times higher in incomplete models

Certain source evolution models are disfavored by gamma-ray data

Abstract

The dip model assumes that the ultra-high energy cosmic rays (UHECRs) above 10$^{18}$ eV consist exclusively of protons and is consistent with the spectrum and composition measure by HiRes. Here we present the range of cosmogenic neutrino fluxes in the dip-model which are compatible with a recent determination of the extragalactic very high energy (VHE) gamma-ray diffuse background derived from 2.5 years of Fermi/LAT data. We show that the largest fluxes predicted in the dip model would be detectable by IceCube in about 10 years of observation and are within the reach of a few years of observation with the ARA project. In the incomplete UHECR model in which protons are assumed to dominate only above 10$^{19}$ eV, the cosmogenic neutrino fluxes could be a factor of 2 or 3 larger. Any fraction of heavier nuclei in the UHECR at these energies would reduce the maximum cosmogenic neutrino fluxes. We also consider here special evolution models in which the UHECR sources are assumed to have the same evolution of either the star formation rate (SFR), or the gamma-ray burst (GRB) rate, or the active galactic nuclei (AGN) rate in the Universe and found that the last two are disfavored (and in the dip model rejected) by the new VHE gamma-ray background.