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Constraints on ultra-heavy dark matter from the CDEX-10 experiment at the China Jinping Underground Laboratory

Y. F. Wang, L. T. Yang, Q. Yue, K. J. Kang, Y. J. Li, H. P. An, Greeshma C., J. P. Chang, H. Chen, Y. H. Chen, J. P. Cheng, J. Y. Cui, W. H. Dai, Z. Deng, Y. X. Dong, C. H. Fang, H. Gong, Q. J. Guo, T. Guo, X. Y. Guo, L. He, J. R. He, H. X. Huang, T. C. Huang, S. Karmakar, Y. S. Lan, H. B. Li, H. Y. Li, J. M. Li, J. Li, M. C. Li, Q. Y. Li, R. M. J. Li, X. Q. Li, Y. L. Li, Y. F. Liang, B. Liao, F. K. Lin, S. T. Lin, J. X. Liu, R. Z. Liu, S. K. Liu, Y. D. Liu, Y. Liu, Y. Y. Liu, H. Ma, Y. C. Mao, A. Mureed, H. Pan, N. C. Qi, J. Ren, X. C. Ruan, M. B. Shen, H. Y. Shi, M. K. Singh, T. X. Sun, W. L. Sun, C. J. Tang, Y. Tian, H. F. Wan, G. F. Wang, J. Z. Wang, L. Wang, Q. Wang, Q. Wang, Y. X. Wang, H. T. Wong, Y. C. Wu, H. Y. Xing, K. Z. Xiong, R. Xu, Y. Xu, T. Xue, Y. L. Yan, N. Yi, C. X. Yu, H. J. Yu, X. Yu, M. Zeng, Z. Zeng, F. S. Zhang, P. Zhang, P. Zhang, Z. Y. Zhang, M. G. Zhao, J. F. Zhou, Z. Y. Zhou, J. J. Zhu

TL;DR

This work develops a comprehensive Monte Carlo framework to predict UHDM energy deposition in $p$-type point-contact germanium detectors at CJPL, explicitly modeling Earth shielding effects. It compares two cross-section models, $A^4$ scaling and per-nucleus scaling, under a standard halo model velocity distribution to generate UHDM spectra and then fits 205.4 kg·day of CDEX-10 data in the 0.16–4.16 keVee range. With no observed excess, the study derives 90% C.L. exclusion regions for UHDM masses from $10^{6}$ to $10^{11}$ GeV, finding the strongest solid-state limits below $10^{8}$ GeV. The results mark the first UHDM limits from a solid-state detector and highlight the impact of Earth shielding on sensitivity, pointing to the upcoming CDEX-50 as a route to stronger constraints.

Abstract

We report a search for ultra-heavy dark matter (UHDM) with the CDEX-10 experiment at the China Jinping Underground Laboratory (CJPL). Using a Monte Carlo framework that incorporates Earth shielding effects, we simulated UHDM propagation and energy deposition in p-type point-contact germanium detectors ($p$PCGe). Analysis of 205.4 kg$\cdot$day exposure in the 0.16-4.16 keVee range showed no excess above background. Our results exclude the spin-independent UHDM-nucleon scattering with two cross section scales, with the UHDM mass from $10^6$ GeV to $10^{11}$ GeV, and provide the most stringent constraints with solid-state detectors below $10^8$ GeV.

Constraints on ultra-heavy dark matter from the CDEX-10 experiment at the China Jinping Underground Laboratory

TL;DR

This work develops a comprehensive Monte Carlo framework to predict UHDM energy deposition in -type point-contact germanium detectors at CJPL, explicitly modeling Earth shielding effects. It compares two cross-section models, scaling and per-nucleus scaling, under a standard halo model velocity distribution to generate UHDM spectra and then fits 205.4 kg·day of CDEX-10 data in the 0.16–4.16 keVee range. With no observed excess, the study derives 90% C.L. exclusion regions for UHDM masses from to GeV, finding the strongest solid-state limits below GeV. The results mark the first UHDM limits from a solid-state detector and highlight the impact of Earth shielding on sensitivity, pointing to the upcoming CDEX-50 as a route to stronger constraints.

Abstract

We report a search for ultra-heavy dark matter (UHDM) with the CDEX-10 experiment at the China Jinping Underground Laboratory (CJPL). Using a Monte Carlo framework that incorporates Earth shielding effects, we simulated UHDM propagation and energy deposition in p-type point-contact germanium detectors (PCGe). Analysis of 205.4 kgday exposure in the 0.16-4.16 keVee range showed no excess above background. Our results exclude the spin-independent UHDM-nucleon scattering with two cross section scales, with the UHDM mass from GeV to GeV, and provide the most stringent constraints with solid-state detectors below GeV.
Paper Structure (8 sections, 9 equations, 5 figures, 1 table)

This paper contains 8 sections, 9 equations, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Derivation of UHDM Spectrum
  3. Procedures
  4. Results and discussion
  5. Data analysis
  6. Procedures
  7. Constraints and discussion
  8. Conclusion

Figures (5)

  • Figure 1: Expectation spectrum for UHDM with $A^4$ scale cross section. The parameters are settled for: (a) Identical cross section as $\sigma_{\chi - n} = 10^{-30}~\mathrm{cm^2}$, and different particle mass including $10^{9}~\mathrm{GeV}$, $10^{10}~\mathrm{GeV}$ and $10^{11}~\mathrm{GeV}$. (b) Identical mass as $10^{10}~\mathrm{GeV}$, and different cross section including $10^{-32}~\mathrm{cm^2}$, $10^{-30}~\mathrm{cm^2}$ and $10^{-29}~\mathrm{cm^2}$. Dashed lines represent the spectra without ESS process. The particles with $\sigma_{\chi-n} = 10^{-32}~\mathrm{cm^2}$ are not affected by ESS, so the red dashed line coincides with the solid line.
  • Figure 2: Structure of the Earth and the path of a UHDM particle (yellow array). The structure species it crosses is determined by the angle $\mathrm{\theta}$.
  • Figure 3: The velocity distribution after shielding ($f(v_{\mathrm{ESS}})$) and expectation spectrum of UHDM contributed by different components. The mass of particle is settled as $10^{10}~\mathrm{GeV}$. $A^4$ scale is used here, and cross section $\sigma_{\chi-n}$ is (a, b) $1\times 10^{-32}~\mathrm{cm^2}$, (c, d) $1\times 10^{-30}~\mathrm{cm^2}$, (e, f) $1\times 10^{-29}~\mathrm{cm^2}$, (g, h) $5\times 10^{-27}~\mathrm{cm^2}$ and (i, j) $5\times 10^{-26}~\mathrm{cm^2}$. As the cross-section increases, UHDM particles of different components become the dominant contributors to the energy spectrum respectively, while their velocity distributions exhibit an increased probability below 100 km/s, contributed by the ESS.
  • Figure 4: (a) The bestfit result for the simulation spectrum with the parameters of $m_{\chi} = 10^{10}~\mathrm{GeV}$ and $\sigma_{\chi - n} = 10^{-33}~\mathrm{cm^2}$, using the $A^4$ cross section scale. CDEX-10 experimental residual spectrum is used in this fit. The energy resolution is considered in this plot, with the standard deviation settled as $\sigma = 35.8 + 16.6\times \sqrt{E}~ (\mathrm{eV})$XR, where $E$ is in keV. (b) Bestfit result for the simulation spectra with same mass ($m_{\chi} = 10^{10}~\mathrm{GeV}$) and different cross section. By using the minimum-$\chi^2$, parameter $\sigma_{\chi - n} = 10^{-33}~\mathrm{cm^2}$ is under the exclusion area, while $\sigma_{\chi - n} = 10^{-32}~\mathrm{cm^2}$ and $\sigma_{\chi - n} = 10^{-30}~\mathrm{cm^2}$ are within the $90\%$ C.L. exclusion area.
  • Figure 5: Exclusion regions with (a) the $A^4$ scale for UHDM mass vs UHDM-nucleon cross section and (b) the A-independent scale for UHDM mass vs UHDM-nucleus cross section. A $90\%$ confidence level (C.L.) one-side upper limit is provided for both exclusions. Our results are compared with those from other direct detection experiments, including Majorana Majorana_UHDM, DAMA dama_UHDM, CDMS and EDELWEISS cdms_UHDMcdms0_UHDM using solid-state detectors, as well as XENON-1T Majorana_UHDM and DEAP-3600 DEAP3600_UHDM using liquid scintillator detectors.