Scrutinizing the cosmogenic origin of the KM3-230213A event: A Multimessenger Perspective

TL;DR

This paper investigates whether the ultra-high-energy neutrino event KM3-230213A has a cosmogenic origin by modeling cosmic-ray interactions and comparing predictions with multimessenger astrophysical data.

Contribution

It presents a self-consistent multimessenger model that constrains the origin of the neutrino event, favoring a hard proton spectrum extending beyond 10^20 eV with specific source evolution.

Findings

A steep sub-ankle proton component is disfavored by gamma-ray background constraints.

A hard proton spectrum with evolution ∝ (1+z)^3 can explain the neutrino event without violating limits.

Constraints on extragalactic cosmic-ray sources are sharpened, guiding future observations.

Abstract

The recent detection of the neutrino event KM3-230213A ($\sim$~220 PeV) by the KM3NeT/ARCA telescope, the most energetic ever observed, could represent the long-awaited evidence for a cosmogenic origin, arising from the interaction of an ultra-high-energy cosmic ray with background photons. Its secure confirmation would mark a major advance in high-energy astrophysics. We perform a self-consistent multimessenger transport calculation of protons and their secondary $\gamma$-rays and neutrinos from cosmologically evolving sources, confronting predictions with data from the Pierre Auger Observatory, IceCube, KM3NeT, and the Fermi-LAT isotropic $\gamma$-ray background. A steep sub-ankle proton component saturates the diffuse $\gamma$-ray background and is disfavoured, whereas a hard proton spectrum extending beyond $10^{20}$~eV with evolution $\propto (1+z)^3$ reproduces KM3-230213A without violating any limits. This scenario requires a proton fraction $\lesssim 10$\% at $3\times 10^{19}$~eV and excludes faster-evolving sources. Joint UHE-neutrino and $\gamma$-ray observations thus sharpen constraints on extragalactic cosmic-ray sources and set targets for AugerPrime and next-generation neutrino telescopes.