Ultrahigh-energy neutrino fluxes and their constraints

Abstract

Applying our recently developed propagation code we review extragalactic neutrino fluxes above 10 14 eV in various scenarios and how they are constrained by current data. We specifically identify scenarios in which the cosmogenic neutrino flux above ≃ 10 18 eV, produced by pion production of ultra high energy cosmic rays outside their sources, is considerably higher than the "WaxmanBahcall bound". This is easy to achieve for sources with hard injection spectra and luminosities that were higher in the past. Such fluxes would significantly increase the chances to detect ultra-high energy neutrinos with experiments currently under construction or in the proposal stage.

Neutrino bounds on astrophysical sources and new physics

“…The latter must therefore inject nucleons with energies of at least 10 12 GeV. Indeed, contributions to the nucleon channel from semi-local sources [37], as well as recently discussed possibilities [38] of source spectra harder than E −1.5 ν and source evolutions stronger than (1 + z) 4 , would all significantly enhance the cosmogenic neutrino flux. Contributions from decaying topological defects, active galactic nuclei, and other speculative sources would have a similar effect.…”

Bounds on the cosmogenic neutrino flux

“…Lower and upper dotted line: flux from Ref. [10], assuming (E max , α, n) = (1×10 21 eV,1.5, 3) and (3×10 22 eV,1.0, 3), respectively, where α denotes the proton injection spectral index (cf. Eq.…”

“…In the following, we make the usual assumption [7,8,9,10,11] that the r and E i dependences of the source luminosity distribution factorize, L p (r, E i ) = ρ(r) J p (E i ), and that the redshift evolution of the sources can be parametrized by a simple power-law,…”

A Search for Ultra-High Energy Neutrinos and Cosmic-Rays with ANITA-2

“…ESS-01 lines show the flux of ν µ for two source evolution scenarios from [51]. The KKSS-02 line shows the flux predicted by [109] in the case of strong source evolution and an injected UHECR spectrum that follows E CR ∝ E −1 .…”