Cosmogenic neutrinos: parameter space and detectabilty from PeV to ZeV

Abstract

Abstract. While propagating from their source to the observer, ultrahigh energy cosmic rays interact with cosmological photon backgrounds and generate to the socalled "cosmogenic neutrinos". Here we study the parameter space of the cosmogenic neutrino flux given recent cosmic ray data and updates on plausible source evolution models. The shape and normalization of the cosmogenic neutrino flux are very sensitive to some of the current unknowns of ultrahigh energy cosmic ray sources and composition. We investigate various chemical compositions and maximum proton acceleration energies E p,max which are allowed by current observations. We consider different models of source evolution in redshift and three possible scenarios for the Galactic to extragalactic transition.We summarize the parameter space for cosmogenic neutrinos into three regions: an optimistic scenario that is currently being constrained by observations, a plausible range of models in which we base many of our rate estimates, and a pessimistic scenario that will postpone detection for decades to come. We present the implications of these three scenarios for the detection of cosmogenic neutrinos from PeV to ZeV (10 14−21 eV) with the existing and upcoming instruments. In the plausible range of parameters, the narrow flux variability in the EeV energy region assures low but detectable rates for IceCube (0.06 − 0.2 neutrino per year) and the Pierre Auger Observatory (0.03 − 0.06 neutrino per year), and detection should happen in the next decade. If EeV neutrinos are detected, PeV information can help select between competing models of cosmic ray composition at the highest energy and the Galactic to extragalactic transition at ankle energies. With improved sensitivity, ZeV neutrino observatories, such as ANITA and JEM-EUSO could explore and place limits on the maximum acceleration energy.

Extragalactic propagation of ultrahigh energy cosmic-rays

“…On the other hand, the maximum energy at the sources must be large enough for particles above the pion production threshold to be present at all redshifts. The influence of composition [157,158,66,160,164] is slightly more complicated to handle, however, for a given maximum energy per nucleon (of course above the pion production threshold) the neutrino flux predicted for heavy primaries (say iron) is lower but comparable with the expectations for proton primaries. The difference depends mostly on the spectral index required to fit the UHECR spectrum (the neutrino deficit for heavy primaries is larger when a soft spectral index is needed) and on the required total injected CR luminosity (which is usually lower in the case of heavy primaries, due to the lower energy losses they experience below 10 19 eV, see Fig .2b and discussion in [165]).…”

Ultrahigh-energy cosmic ray production by turbulence in gamma-ray burst jets and cosmogenic neutrinos

“…The thin lines show the all-flavour cosmogenic neutrino intensities for the models A-D, which are below the upper limits (grey shaded area) by IceCube taken from Heinze et al [80] based on Ishihara [81], and ANITA-II [82]. For comparison, we also plot the model spectra of the cosmogenic neutrinos by Kotera et al [83] (thin dotted line, denoted as KAO10) and prompt plus cosmogenic neutrinos by Asano and Mészáros [22] (thin dashed line, denoted as AM14).…”

“…4) at 10 19 eV (the typical energy of the parent protons for such neutrinos) are also close to each other. As a representative model characteristic of previous studies, we also plot the GZK neutrino spectrum for the ankle transition model by Kotera et al [83] (WW model), in which UHECRs are injected with a power-law spectrum of p = 2.1 and a cut-off energy of 10 20.5 eV following the star formation rate derived in Hopkins and Beacom [86]. The total neutrino spectrum (prompt plus cosmogenic) based on the shock acceleration in GRBs by Asano and Mészáros [22] (the injection spectrum is shown in Fig.…”

Radio Cherenkov signals from the Moon: Neutrinos and cosmic rays

“…[30] and three models for the flux of cosmogenic neutrinos (dashed) from Ref. [9] with the assumption of proton primaries. [29].…”