Neutrinos from Primordial Black Holes in Theories with Extra Dimensions

TL;DR

This work links the KM3-230213A high-energy neutrino to a UV-complete scenario with large extra dimensions by proposing Hawking evaporation of 5D primordial black holes residing in the bulk. Emission is dominated by bulk gravitons and sterile neutrinos, with SM brane emission suppressed until the final evaporation stage, naturally avoiding gamma-ray constraints. Sterile-active oscillations induced by shortcuts through the extra dimension can convert bulk sterile neutrinos into active neutrinos with a resonant enhancement near $E_\nu \sim 10^8$ GeV, yielding a neutrino-line feature without a photon counterpart. The authors argue that the required PBH abundance is extremely small relative to dark matter and remains compatible with IceCube bounds on superheavy dark matter decays, offering a testable link between quantum gravity effects and high-energy neutrino observations, and they discuss memory-burdened PBHs as potential DM candidates in this framework.

Abstract

The quantum gravity scale within the dark dimension scenario ($M_* \sim 10^{9}~{\rm GeV}$) roughly coincides with the energy scale of the KM3-230213A neutrino ($E_ν\sim 10^{8}~{\rm GeV}$). We propose an interpretation for this intriguing coincidence in terms of Hawking evaporation of five-dimensional (5D) primordial black holes (PBHs). 5D PBHs are bigger, colder, and longer-lived than 4D PBHs of the same mass. For brane observers, PBHs residing in the higher-dimensional bulk decay essentially invisibly (only through gravitationally and sterile coupled modes). As a consequence, constraints on the density of PBHs relative to that of dark matter from null searches of Hawking evaporation can be avoided. We demonstrate that Hawking evaporation of 5D bulk PBHs can explain the KM3-230213A neutrino, evade constraints from upper limits on the gamma-ray flux, and remain consistent with IceCube upper limits on the partial decay width of superheavy dark matter particles into neutrinos.

Figures (3)

• Figure 1: Schematic representation of the propagation of a sterile neutrino through a geodesic in the bulk and an active neutrino confined to the brane Pas:2005rb.
• Figure 2: Oscillation amplitude $\sin^2 (2\tilde{\theta})$ as a function of the neutrino energy $E_\nu$, for a resonance energy of $E_{\rm res} = 10^8~{\rm GeV}$.
• Figure 3: Schematic representation of a 5D black hole localized on the brane.