S.M. Lee, G. Adhikari, N. Carlin, J.Y. Cho, J.J. Choi, S. Choi, A.C. Ezeribe, L.E. França, 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, S.W. Kim, W.K. Kim, Y.D. Kim, Y.H. Kim, Y.J. Ko, D.H. Lee, E.K. Lee, H. Lee, H.Y. Lee, I.S. Lee, J. Lee, J.Y. Lee, M.H. Lee, S.H. Lee, Y.J. Lee, D.S. Leonard, N.T. Luan, B.B. Manzato, R.H. Maruyama, R.J. Neal, J.A. Nikkel, 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, A. Scarff, M.K. Son, N.J.C. Spooner, L.T. Truc, L. Yang, G.H. Yu
We present a comprehensive study of the nonproportionality of NaI(Tl) scintillation detectors within the context of dark matter search experiments. Our investigation, which integrates COSINE-100 data with supplementary γ spectroscopy, measures light yields across diverse energy levels from full-energy γ peaks produced by the decays of various isotopes. These γ peaks of interest were produced by decays supported by both long and short-lived isotopes. Analyzing peaks from decays supported only by short-lived isotopes presented a unique challenge due to their limited statistics and overlapping energies, which was overcome by long-term data collection and a time-dependent analysis. A key achievement is the direct measurement of the 0.87 keV light yield, resulting from the cascade following electron capture decay of 22Na from internal contamination. This measurement, previously accessible only indirectly, deepens our understanding of NaI(Tl) scintillator behavior in the region of interest for dark matter searches. This study holds substantial implications for background modeling and the interpretation of dark matter signals in NaI(Tl) experiments. © The Author(s) 2024.
Department of Physics and Astronomy, Seoul National University, Seoul, 08826, South Korea; Department of Physics and Wright Laboratory, Yale University, New Haven, 06520, CT, United States; Physics Institute, University of São Paulo, São Paulo, 05508-090, Brazil; Center for Underground Physics, Institute for Basic Science (IBS), Daejeon, 34126, South Korea; Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, United Kingdom; Department of Physics, Chung-Ang University, Seoul, 06973, South Korea; Center for Exotic Nuclear Studies, Institute for Basic Science (IBS), Daejeon, 34126, South Korea; Department of Science Education, Ewha Womans University, Seoul, 03760, South Korea; IBS School, University of Science and Technology (UST), Daejeon, 34113, South Korea; Department of Physics and Wisconsin IceCube Particle Astrophysics Center, University of Wisconsin-Madison, Madison, 53706, WI, United States; Department of Physics, Kyungpook National University, Daegu, 41566, South Korea; Department of Physics, Sejong University, Seoul, 05006, South Korea; Korea Research Institute of Standards and Science, Daejeon, 34113, South Korea; Department of Accelerator Science, Korea University, Sejong, 30019, South Korea; Department of Physics and IQS, Chungnam National University, Daejeon, 34134, South Korea; Department of Physics, Universitas Negeri Malang, Malang, 65145, Indonesia; Department of Physics, Sungkyunkwan University, Suwon, 16419, South Korea; Department of Physics and Astronomy, University of Utah, Salt Lake City, 84112, UT, United States