Search for boosted keV-MeV light dark matter particles from evaporating primordial black holes at the CDEX-10 experiment

We present novel constraints on boosted light dark matter particles (denoted as ``$χ$'') from evaporating primordial black holes (PBHs) using 205.4 kg·day data from the China Jinping Underground Laboratory's CDEX-10 p-type point contact germanium detector with a 160 eVee analysis threshold. $χ$ from PBHs with masses ranging from 1×10¹⁵ g to 7×10¹⁶ g are searched in this work. In the presence of PBH abundance compatible with present bounds, our result excludes the $χ$-nucleon elastic-scattering cross section region from 3.4×10⁻³² cm² to 2.3×10⁻²⁹ cm² for $χ$ of 1 keV to 24 MeV from PBHs with masses of 5×10¹⁵ g, as well as from 1.1×10⁻²⁸ cm² to 7.6×10⁻²⁸ cm² for $χ$ of 1 keV to 0.6 MeV from PBHs with masses of 7×10¹⁶ g. If the $χ$-nucleon elastic-scattering cross section can be determined in the future, the abundance of PBHs may be severely constrained by $χ$ evaporation. With the lower threshold (160 eVee) of the CDEX-10 experiment compared to the previously used experiments, this work allows for a better reach at soft spectra produced by heavier PBHs, which demonstrates the vast potential of such a technical route to pursue $χ$ from larger PBHs with a low threshold.