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First search for light fermionic dark matter absorption on electrons using germanium detector in CDEX-10 experiment

J. X. Liu, L. T. Yang, Q. Yue, K. J. Kang, Y. J. Li, H. P. An, Greeshma C., J. P. Chang, Y. H. Chen, J. P. Cheng, W. H. Dai, Z. Deng, C. H. Fang, X. P. Geng, H. Gong, Q. J. Guo, T. Guo, X. Y. Guo, L. He, J. R. He, J. W. Hu, H. X. Huang, T. C. Huang, L. Jiang, S. Karmakar, 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, S. K. Liu, Y. D. Liu, Y. Liu, Y. Y. Liu, H. Ma, Y. C. Mao, Q. Y. Nie, H. Pan, N. C. Qi, J. Ren, X. C. Ruan, M. B. Shen, M. K. Singh, T. X. Sun, W. L. Sun, C. J. Tang, Y. Tian, G. F. Wang, J. Z. Wang, L. Wang, Q. Wang, Y. F. 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, M. Zeng, Z. Zeng, B. T. Zhang, F. S. Zhang, L. Zhang, P. Zhang, Z. H. Zhang, Z. Y. Zhang, J. Z. Zhao, K. K. Zhao, M. G. Zhao, J. F. Zhou, Z. Y. Zhou, J. J. Zhu

Abstract

We present the first results of the search for sub-MeV fermionic dark matter absorbed by electron targets of germanium using the 205.4~kg$\cdot$day data collected by the CDEX-10 experiment, with the analysis threshold of 160~eVee. No significant dark matter (DM) signals over the background are observed. Results are presented as limits on the cross section of DM--electron interaction. We present new constraints of cross section in the DM range of 0.1--10 keV/$c^2$ for vector and axial-vector interaction. The upper limit on the cross section is set to be $\rm 6.8\times10^{-46}~cm^2$ for vector interaction, and $\rm 2.3\times10^{-46}~cm^2$ for axial-vector interaction at DM mass of 5 keV/$c^2$.

First search for light fermionic dark matter absorption on electrons using germanium detector in CDEX-10 experiment

Abstract

We present the first results of the search for sub-MeV fermionic dark matter absorbed by electron targets of germanium using the 205.4~kgday data collected by the CDEX-10 experiment, with the analysis threshold of 160~eVee. No significant dark matter (DM) signals over the background are observed. Results are presented as limits on the cross section of DM--electron interaction. We present new constraints of cross section in the DM range of 0.1--10 keV/ for vector and axial-vector interaction. The upper limit on the cross section is set to be for vector interaction, and for axial-vector interaction at DM mass of 5 keV/.
Paper Structure (10 equations, 4 figures, 2 tables)

This paper contains 10 equations, 4 figures, 2 tables.

Figures (4)

  • Figure 1: Predicted visible energy spectra of the fermionic DM absorbed by electron targets of Ge for a vector-type operator for $m_\chi$ = 2 keV/$c^2$ and $\sigma_e v_\chi$ = $10^{-45}$ cm$^2$. Contributions by different shells of electrons are shown in different colors. The signals used in this analysis (summation from $1s$ to $3d$) are shown in gray shade. In this scenario with $m_\chi$ = 2 keV/$c^2$, $K$-shell ($n$=1) electrons cannot be ionized due to the small $m_\chi$. The $N$-shell ($n$=4) spectra shown here is calculated assuming Ge atoms as isolated atoms, but the contribution from the $N$ shell is not included. The energy resolution is not considered in this figure.
  • Figure 2: Expected HPGe detector response in the vector interaction case at $\sigma_e v_\chi =\rm 10^{-45}~cm^2$ for $m_\chi =\rm 2~keV/c^2$ (blue) and $m_\chi =\rm 12~keV/c^2$ (red) are superimposed. Experimental data from CDEX-10 before combined efficiency correction in 0.16-2.16 keVee are also depicted. The bin width is 100 eVee.
  • Figure 3: The spectrum from CDEX-10 (black point with error bar), together with the best-fit signal (red dotted line) for $m_\chi$ = 12 keV/$c^2$. The light blue solid line is the best fit for the background. The red solid line is the summation of the best fits of signal and background. The contribution from isotope $\rm ^{68}Ga~(M)$ is too small to be seen in this plot.
  • Figure 4: The 90% confidence level (CL) exclusion limits on $\sigma_e v_\chi$ of the fermionic DM absorbed by electron target for the (a) axial-vector operator and (b) vector operator from CDEX-10 is shown in red. Results from PandaX-4T FDEA_3_PandaX (blue) are superimposed. The exclusion regions of direct detection experiments are shown with shade. Results of DM invisible decay($\chi \rightarrow 3\nu$) and overproduction for both operators and DM visible decay($\chi\rightarrow\gamma\gamma\nu$) for the axial-vector operator are also shown (dashed dot line) FDEA_1_GSFCMB_Plank.