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Limits on WIMP dark matter with NaI(Tl) crystals in three years of COSINE-100 data

G. H. Yu, N. Carlin, J. Y. Cho, J. J. Choi, S. Choi, A. C. Ezeribe, L. E. Franca, C. Ha, I. S. Hahn, S. J. Hollick, E. J. Jeon, H. W. Joo, W. G. Kang, M. Kauer, B. H. Kim, H. J. Kim, J. Kim, K. W. Kim, S. H. Kim, S. K. Kim, W. K. Kim, Y. D. Kim, Y. H. Kim, Y. J. Ko, D. H. Lee, E. K. Lee, H. Lee, H. S. Lee, H. Y. Lee, I. S. Lee, J. Lee, J. Y. Lee, M. H. Lee, S. H. Lee, S. M. Lee, Y. J. Lee, D. S. Leonard, N. T. Luan, V. H. A. Machado, B. B. Manzato, R. H. Maruyama, R. J. Neal, S. L. Olsen, B. J. Park, H. K. Park, H. S. Park, J. C. Park, K. S. Park, S. D. Park, R. L. C. Pitta, H. Prihtiadi, S. J. Ra, C. Rott, K. A. Shin, D. F. F. S. Cavalcante, M. K. Son, N. J. C. Spooner, L. T. Truc, L. Yang

Abstract

We report limits on WIMP dark matter derived from three years of data collected by the COSINE-100 experiment with NaI(Tl) crystals, achieving an improved energy threshold of 0.7 keV. This lowered threshold enhances sensitivity in the sub-GeV mass range, extending the reach for direct detection of low-mass dark matter. Although no excess of WIMP-like events was observed, the increased sensitivity enabled a model-insensitive comparison between the expected WIMP signal rate-based on mass limits from our data-and DAMA's reported modulation amplitude. Our findings strongly disfavor the DAMA signal as originating from WIMP interactions, fully excluding DAMA/LIBRA 3$σ$ allowed regions and providing enhanced WIMP mass limits by an order of magnitude in the spin-independent model compared to previous results. In the spin-dependent model, cross-section upper limits were obtained in the mass range [0.1-5.0] GeV/c$^2$, with additional sensitivity to sub-GeV WIMPs through the inclusion of the Migdal effect. These results represent substantial progress in low-mass dark matter exploration and reinforce constraints on the longstanding DAMA claim.

Limits on WIMP dark matter with NaI(Tl) crystals in three years of COSINE-100 data

Abstract

We report limits on WIMP dark matter derived from three years of data collected by the COSINE-100 experiment with NaI(Tl) crystals, achieving an improved energy threshold of 0.7 keV. This lowered threshold enhances sensitivity in the sub-GeV mass range, extending the reach for direct detection of low-mass dark matter. Although no excess of WIMP-like events was observed, the increased sensitivity enabled a model-insensitive comparison between the expected WIMP signal rate-based on mass limits from our data-and DAMA's reported modulation amplitude. Our findings strongly disfavor the DAMA signal as originating from WIMP interactions, fully excluding DAMA/LIBRA 3 allowed regions and providing enhanced WIMP mass limits by an order of magnitude in the spin-independent model compared to previous results. In the spin-dependent model, cross-section upper limits were obtained in the mass range [0.1-5.0] GeV/c, with additional sensitivity to sub-GeV WIMPs through the inclusion of the Migdal effect. These results represent substantial progress in low-mass dark matter exploration and reinforce constraints on the longstanding DAMA claim.
Paper Structure (4 equations, 4 figures)

This paper contains 4 equations, 4 figures.

Figures (4)

  • Figure 1: A comparison of MLP selection efficiency down to 0.7 keV between the 1$\sigma$ band of COSINE-100 C2 and the electron-recoil and nuclear-recoil selection efficiencies from the NaI(Tl) crystal sample.
  • Figure 2: Results of background modeling for (top) single- and (bottom) multiple-hit events summed over five crystals, shown with the 1 and 2 $\sigma$ systematic uncertainty band.
  • Figure 3: Fit example of WIMP presence test on COSINE-100 3-year data, considering SI model and $m_{\chi}$=11.5 GeV/$c^2$. The expected spectrum based on DAMA/LIBRA's observation($\sigma_{\text{SI}}=1.5\times10^{-4}$ pb, without Migdal) is shown as a red dashed line.
  • Figure 4: The COSINE-100 3-year 90% C.L. upper limits on (a) SI and (b) SD WIMP-nucleon cross sections. In (a), the DAMA/LIBRA 3$\sigma$ region is overlaid for comparison. In (b), leading experimental constraints are shown, and the COSINE-100 SD limits, including the Migdal effect, extend sensitivity to the sub-GeV masses. Furthermore, more stringent limits are expected from COSINE-100U.