High-Energy Neutrinos from Black Hole Evaporation in Neutron Stars

Abstract

We investigate the production of high-energy neutrinos from microscopic black holes formed through the gravitational collapse of asymmetric dark matter accumulated inside neutron stars. When Hawking evaporation dominates over accretion, long-lived, feebly interacting particles beyond the Standard Model escape the neutron star and subsequently decay into high-energy neutrinos. We analyze the repeated cycle of dark matter capture, black hole formation, and evaporation, identifying two distinct regimes determined by the competition between the dark matter thermalization time and the collapse cycle. In particular, we identify a partially thermalized regime in which the dark matter cloud evolves toward a quasi-stationary state with a temperature significantly exceeding that of the neutron star core. We derive the time-integrated Hawking emission, the resulting secondary neutrino spectra, and the expected Galactic and diffuse extragalactic neutrino fluxes. The predicted signal exhibits two distinctive signatures: a broad neutrino spectrum with a characteristic energy scale set by the initial Hawking temperature of the evaporating black hole, whose spectral peak naturally lies above $\mathcal{O}(10)$ TeV, and an extended Galactic component strongly concentrated toward the Galactic Center. Although the predicted event rates are generally small, the resulting signal may contribute at the percent level to the observed Galactic high-energy neutrino flux under favorable microscopic and astrophysical conditions. The proposed mechanism provides a new observational window on Hawking evaporation through microscopic black holes continuously produced inside neutron stars, linking dark matter, compact objects, black hole thermodynamics and high-energy neutrino astronomy.