Identifying Spin Properties of Evaporating Black Holes through Asymmetric Neutrino and Photon Emission

TL;DR

This paper investigates how asymmetric neutrino and photon emissions from evaporating black holes can reveal their spin properties and orientation, especially for nearby primordial black holes during their final explosive stages.

Contribution

It introduces a detailed analysis of anisotropic particle emissions from Kerr black holes, improving previous models by considering Earth's privileged viewing angle and exploring observational signatures.

Findings

Neutrino emissions are asymmetric and can indicate black hole spin orientation.

Photon spectra show angular dependence, aiding in black hole characterization.

Neutrino detection is feasible for black holes within 10^{-4} parsecs during the last 100 seconds of evaporation.

Abstract

Kerr black holes radiate neutrinos in an asymmetric pattern, preferentially in the lower hemisphere relative to the black hole's rotation axis, while antineutrinos are predominantly produced in the upper hemisphere. Leveraging this asymmetric emission, we explore the potential of high-energy, $E_\nu \gtrsim 1$ TeV, neutrino and antineutrino detection to reveal crucial characteristics of an evaporating primordial black hole at the time of its burst when observed near Earth. We improve upon previous calculations by carefully accounting for the non-isotropic particle emission, as Earth occupies a privileged angle relative to the black hole's rotation axis. Additionally, we investigate the angular dependence of primary and secondary photon spectra and assess the evaporating black hole's time evolution during the final explosive stages of its lifetime. Since photon events outnumber neutrinos by about three orders of magnitude, we find that a neutrino measurement can aid in identifying the initial angular momentum and the black hole hemisphere facing Earth only for evaporating black holes within our solar system, at distances $\lesssim 10^{-4}$ pc, and observed during the final 100 s of their lifetime.