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 ``$\chi$’') from evaporating primordial black holes (PBHs) using 205.4 kg$\cdot$day data from the China Jinping Underground Laboratory’s CDEX-10 p-type point contact germanium detector with a 160 eVee analysis threshold. $\chi$ from PBHs with masses ranging from 1$\times$10${}^{15}$ g to 7$\times$10${}^{16}$ g are searched in this work. In the presence of PBH abundance compatible with present bounds, our result excludes the $\chi$-nucleon elastic-scattering cross section region from 3.4$\times$10${}^{-32}$ cm${}^2$ to 2.3$\times$10${}^{-29}$ cm${}^2$ for $\chi$ of 1 keV to 24 MeV from PBHs with masses of 5$\times$10${}^{15}$ g, as well as from 1.1$\times$10${}^{-28}$ cm${}^2$ to 7.6$\times$10${}^{-28}$ cm${}^2$ for $\chi$ of 1 keV to 0.6 MeV from PBHs with masses of 7$\times$10${}^{16}$ g. If the $\chi$-nucleon elastic-scattering cross section can be determined in the future, the abundance of PBHs may be severely constrained by $\chi$ 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 $\chi$ from larger PBHs with a low threshold.