Primordial black holes as cosmic accelerators of light dark matter: Novel direct detection constraints

TL;DR

Primordial black holes can emit boosted light dark sector particles via Hawking radiation, producing a relativistic DM flux that can generate electron recoils in direct-detection experiments. The authors compute the PBH-evaporated DM flux, treat constant, scalar, and vector DM–electron cross sections with full relativistic kinematics, and model Earth attenuation numerically to derive 90% CL constraints from XENONnT, LZ, and PandaX-4T, with prospects for Super-K and Hyper-K. They demonstrate that attenuation and the Lorentz structure of the interaction shape recoil spectra and bounds, enabling competitive constraints on PBH abundance $f_ ext{PBH}$ and offering a complementary probe to traditional cosmological limits. This work establishes a robust framework to explore light dark sectors and PBHs with terrestrial detectors, emphasizing realistic cross sections and in-medium effects.

Abstract

Current multiton dark matter (DM) detectors are largely incapable of detecting light dark matter from the Galactic halo due to the energy threshold limitations of their recoil measurements. However, primordial black holes (PBHs) can evaporate via Hawking radiation to particles whose energies are set by the black hole temperature. Consequently, weakly interacting light dark matter (or dark radiation) particles produced in this manner can reach the Earth with sufficient flux and kinetic energy above the experimental thresholds. This opens up a novel avenue to probe the light dark sector in terrestrial experiments. In this work, we explore this possibility by considering fermionic DM produced through PBH evaporation and investigate its electron recoil signatures in direct detection experiments. We analyze both energy independent (constant) and energy dependent (scalar and vector mediated) DM-electron interactions, highlighting the strong dependence of the recoil spectra on the underlying Lorentz structure of the interaction. In addition, we also account for the attenuation effects due to loss of kinetic energy while DM traverses through Earth's crust, which can significantly modify the incoming DM flux. Incorporating these effects carefully, we place constraints on light DM using the electron recoil data from XENONnT, LZ, and PandaX-4T. Finally, we also discuss the detection prospects of such dark matter in current and future generation neutrino detectors, such as Super Kamiokande and Hyper Kamiokande.

Figures (17)

• Figure 1: Differential DM flux per unit solid angle, $\mathop{}\!\mathrm{d}^{2}\Phi_\chi/\mathop{}\!\mathrm{d} T_\chi\,\mathop{}\!\mathrm{d}\Omega$, from PBH evaporation as a function of the DM kinetic energy $T_\chi$ for a DM mass of $m_\chi = 1~\mathrm{MeV}$. Results are shown for two benchmark PBH masses, $M_{\rm PBH}=10^{15}~\mathrm{g}$ (red) and $10^{16}~\mathrm{g}$ (blue), with corresponding PBH abundance fractions consistent with cosmological limits, $f_{\rm PBH}=3.9\times10^{-7}$ and $5.9\times10^{-4}$, respectively. For each benchmark, the Galactic (dashed), extragalactic (dash–dotted), and total (solid) flux components are displayed.
• Figure 2: The event spectra of $e$ upon being scattered by $\chi$ evaporated from a PBH with $M_{\rm PBH}=10^{15}$ gm and $f_{\rm PBH}=3.9 \times 10^{-7}$ in (a) XENONnT, (b) LZ and (c) PandaX-4T. Rates for different cross-sections e.g constant (magenta), vector (red) and scalar (blue) are depicted by different solid colored lines. Grey region signifies the known backgrounds denoted as $B_0$ where as the black dots with (without in (b)) error bars signify the observed event data.
• Figure 3: Constant cross-section: Constraints at $90\%$ C.L. on DM $\chi$ with constant cross-section evaporated from PBH using XENONnT (light blue), PandaX-4T (light yellow) and LZ (light red) . Chosen PBH BPs are (a) $M_{\rm PBH}=10^{15}$gm with $f_{\rm PBH}=3.9\times 10^{-7}$ and (b) $M_{\rm PBH}=10^{16}$gm with $f_{\rm PBH}=5.9\times 10^{-4}$. Other existing constraints are also displayed.
• Figure 4: Vector cross-section: Constraints at $90\%$ C.L. on DM $\chi$ with vector cross-section evaporated from PBH using XENONnT (light blue), PandaX-4T (light yellow) and LZ (light red) . Chosen PBH BPs are (a) $M_{\rm PBH}=10^{15}$gm with $f_{\rm PBH}=3.9\times 10^{-7}$ and (b) $M_{\rm PBH}=10^{16}$gm with $f_{\rm PBH}=5.9\times 10^{-4}$. Other existing constraints are also displayed.
• Figure 5: Scalar cross-section: Constraints at $90\%$ C.L. on DM $\chi$ with scalar cross-section evaporated from PBH using XENONnT (light blue), PandaX-4T (light yellow) and LZ (light red) . Chosen PBH BPs are (a) $M_{\rm PBH}=10^{15}$gm with $f_{\rm PBH}=3.9\times 10^{-7}$ and (b) $M_{\rm PBH}=10^{16}$gm with $f_{\rm PBH}=5.9\times 10^{-4}$. Other existing constraints are also displayed.