Mineral Detection of Cosmic-Ray Boosted Dark Matter

Abstract

We present the first dedicated analysis of cosmic-ray dark matter (CRDM) in paleo detectors. Owing to their large kinetic energies, CRDM particles generate nuclear-recoil tracks that extend to substantially larger lengths than those produced by dominant backgrounds from neutrinos and intrinsic radioactivity. Combined with the ultra-large effective geological exposure of $\mathcal{O}(10^{5})~\mathrm{t\,yr}$, paleo detectors provide a uniquely sensitive probe of sub-GeV DM. Considering both constant and vector-mediator interactions, we find that paleo detectors improve the sensitivity to the DM--proton scattering cross section by one to two orders of magnitude compared with the latest XENONnT limits.

Figures (3)

• Figure 1: Differential flux of CRDM for the vector-mediator model. (Top) Total CRDM spectrum (solid black) and the individual contributions from different cosmic-ray species (dashed), assuming $g_\chi=g_q=0.1$, $m_V=1~{\rm GeV}$, and $m_\chi=0.1~{\rm GeV}$. (Bottom) Impact of inelastic scattering on the CRDM flux: the solid curves include both elastic and deep-inelastic scattering (EL+DIS), while the dashed curves show the elastic-only contribution (EL). Different colours correspond to different DM mass $m_\chi$, namely $m_\chi=100~{\rm MeV}$ (black), $10~{\rm MeV}$ (red), and $1~{\rm MeV}$ (blue).
• Figure 2: Binned track length distributions in Gypsum [$\mathrm{Ca(SO_4)\!\cdot\!2(H_2O)}$] for CRDM in the vector-mediator model. The red and blue curves show CRDM signals for $m_\chi=10^{-5}~\mathrm{GeV}$ and $10^{-3}~\mathrm{GeV}$, respectively, while the black, orange, and green curves denote the dominant nuclear recoil backgrounds from neutrinos, radiogenic neutrons, and $^{238}\mathrm{U}\!\rightarrow\!^{234}\mathrm{Th}+\alpha$ decays. The input parameters are $g_\chi=g_q=0.1$ and $m_V=1~\mathrm{GeV}$.
• Figure 3: Constraints on the DM--proton scattering cross section as a function of the DM mass. The purple and green curves show the projected sensitivities of paleo detectors using Gypsum and Olivine, respectively, while the red curves indicate the XENONnT limits. The dotted curves correspond to the constant cross section scenario, whereas the dashed and solid curves denote the vector-mediator model with $m_V=10~\mathrm{MeV}$ and $m_V=1~\mathrm{GeV}$. Existing constraints from PandaX-4T PandaX:2023xgl, SENSEI SENSEI:2023zdf, and BBN Giovanetti:2021izc are shown for comparison.