The Maximal Gravitational Wave Signal from Asteroid-Mass Primordial Black Hole Mergers At Resonant Microwave Cavities

TL;DR

This paper evaluates the potential for detecting gravitational waves from asteroid-mass primordial black hole mergers using resonant microwave cavities, highlighting the rarity of such events despite updated detection calculations.

Contribution

It updates the calculation of detection distances and event rates for primordial black hole mergers in the asteroid-mass range using resonant microwave cavities.

Findings

Maximal detection rates are linked to binaries from non-monochromatic mass functions.

Detection events are predicted to be extremely rare even under optimistic conditions.

Resonant microwave cavities have limited sensitivity for these black hole mergers.

Abstract

Primordial black holes can be the entirety of the dark matter in a broad, approximately five-orders-of-magnitude-wide mass range, the ``asteroid mass range'', between $10^{-16}\ M_{\rm Sun}$ -- where constraints originate from evaporation -- and $10^{-11}\ M_{\rm Sun}$ -- from microlensing. A direct detection in this mass range is very challenging with any known observational or experimental methods. Here we update the calculation of the sight distance for narrow-band detectors such as resonant microwave cavities, and the resulting maximal event rate. We find that the largest detection rates are associated with binaries from non-monochromatic mass functions in early-formed three-body systems. Even in the most optimistic setup, these events are anticipated to be extremely rare.