Ultra-high energy event KM3-230213A as a cosmogenic neutrino in light of minimal UHECR flux models

Abstract

Recently, the KM3NeT experiment reported the detection of a neutrino with exceptionally high energy E = 220 PeV, whose origin remains unclear. The corresponding value of the neutrino flux is in tension with the results of other high-energy neutrino experiments. In this study, we discuss the possibility that this neutrino is cosmogenic, i. e., produced by ultra-high energy cosmic rays (UHECR) during their propagation through the intergalactic medium. We adopt the UHECR flux models derived by the Telescope Array experiment, which features a predominantly light mass composition. We show that the predictions of the cosmogenic neutrino flux in these models are consistent with the measurements of the KM3NeT-only and with that of the "global neutrino observatory" at approximately 2$σ$ level. Notably, this result is achieved in a minimal version of the UHECR flux models, that assume one source population with a standard cosmological evolution. We also estimate the corresponding cosmogenic gamma-ray flux and show that it is consistent with Fermi-LAT IGRB measurements and UHE gamma-ray limits; the improvement of the latter can probe these predictions in future.

Figures (5)

• Figure 1: Effective areas of the experiments used in this work. These are full-sky averages, summed over all neutrino flavors, and averaged over both neutrinos and antineutrinos.
• Figure 2: Simulated spectra of UHECR mass components according to the TA flux models (solid lines). The upper and lower plots correspond to the best-fit and local min. models, respectively. Black dots with error bars --- all-particle UHECR spectrum measured with the TA SD.
• Figure 3: Energy-squared per-flavour neutrino fluxes, assuming neutrino equipartition ($\nu_e:\nu_\mu:\nu_\tau = 1:1:1$). Red and olive crosses denote KM3NeT-only measurement KM3NeT:2025npi and combined $E^{-2}$ fit Baikal-GVD:2025kbe. Vertical bars represent the $1\sigma$, $2\sigma$, $3\sigma$ and $1\sigma$ Feldman–Cousins confidence intervals Feldman:1997qc of these estimates respectively. Blue and green solid lines show the fluxes for the best-fit and local min. models, respectively.
• Figure 4: Energy spectrum of cascade photons. Blue and green solid lines represent the estimated flux for the best-fit and local min. models, respectively. Red points with error bars represent the Fermi IGRB measurements for galactic foreground model B Fermi-LAT:2014ryh.
• Figure 5: Upper limits on the integral UHE gamma ray flux. Here we compare predictions of the models (solid lines) with the observations (markers with downward arrows). Upper limits from Auger PierreAuger:2024aylPierreAuger:2022aty are marked in green and orange, limits from TA TelescopeArray:2018rbtKharuk:2023gts are marked in pink and purple, limits from KASCADE(-Grande) KASCADEGrande:2017vwf are marked in red and limits from EAS-MSU Fomin:2017ypo are marked in teal. Blue and green solid lines correspond to the best-fit and local min. models, accordingly.