Boosted dark matter from primordial black holes produced in a first-order phase transition

TL;DR

Addresses whether a cosmological first-order phase transition in a dark sector can form Fermi balls that collapse into PBHs, whose Hawking evaporation yields a boosted $χ$ flux detectable via electron scattering. It builds a predictive framework coupling FB/PBH dynamics to Hawking emission, computes the boosted-$χ$ flux at Earth, and evaluates DM event rates in XENONnT/XENON1T and SK/HK, plus GW signals at THEIA/$μ$Ares and $\Delta N_{ m eff}$ in CMB-S4. A parameter-space scan reveals regions where joint DM signals and GW detections are possible while obeying cosmological bounds, and six benchmark points illustrate the expected spectra. This work provides a concrete link between early-Universe phase transitions, PBH production, boosted dark matter, and upcoming multi-messenger probes.

Abstract

During a cosmological first-order phase transition in a dark sector, fermion dark matter particles $χ$ can form macroscopic Fermi balls that collapse to primordial black holes (PBHs) under certain conditions. The evaporation of the PBHs produces a boosted $χ$ flux, which may be detectable if $χ$ couples to visible matter. We consider the interaction of $χ$ with electrons, and calculate signals of the dark matter flux in the XENON1T, XENONnT, Super-Kamiokande and Hyper-Kamiokande experiments. A correlated gravitational wave signal from the phase transition can be observed at THEIA and $μ$Ares. An amount of dark radiation measurable by CMB-S4 is an epiphenomenon of the phase transition.

Figures (2)

• Figure 1: The parameter space in which a GW signal can be detected at THEIA/$\mu$Ares is shown with green points. The yellow points are excluded by current XENON1T/XENONnT/SK data at $2\sigma$, and the red points are consistent with these data at $2\sigma$, but can produce a $2\sigma$ DM signal in future XENONnT/HK data and a GW signal at THEIA/$\mu$Ares. The solid black curve in the top left panel shows the current bound from observations of the extragalactic gamma-ray background and from the damping of small scale CMB anisotropies. The stars mark the six benchmark points in Table \ref{['tab:BP']}. All points satisfy $\Omega_{\rm PBH} h^2 \leq 0.12$, $\Delta N_{\rm eff}\leq 0.5$ and $m_\chi(T_\star)-m > 2 T_{{\rm SM}\star}$.
• Figure 2: Gravitational wave spectra for the benchmark points in Table \ref{['tab:BP']}.