Achieving a 0.49 keV threshold in the COSINE-100 dark matter experiment

The COSINE-100 experiment searched for weakly interacting massive particles (WIMPs) with NaI(Tl) crystals at the Yangyang Underground Laboratory. Using its full 6-year dataset, we lower the analysis threshold to 0.49 keV. A multi-layer perceptron classifier separates scintillation events from photomultiplier tube noise. It is trained with approximately $3\times10^{6}$ simulated scintillation waveforms per crystal, separately for groups of events with similar numbers of photoelectron clusters. The selection keeps more than 10% of scintillation events at 0.49 keV while limiting noise contamination to below 1%. The selection efficiency is validated with $^{22}$Na-calibration data and internal $^{22}$Na events, and the selection performance is stable over the six years of data taking. With this threshold, the median expected upper limit on the spin-dependent WIMP-proton cross section reaches $1.1\times10^{-36}$ cm$^2$ at a WIMP mass of 2.5 GeV/$c^2$, probing previously unexplored parameter space in the 2.0-2.8 GeV/$c^2$ mass range.

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Authors

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

Published

Oct 14, 2026

Paper type

preprint

Source

Arxiv