COSINE-100: Full dataset challenges the annual modulation signal of DAMA/LIBRA

For over 25 years, the DAMA/LIBRA collaboration has claimed to observe an annual modulation signal, suggesting the existence of dark matter interactions. However, no experiment employing different target materials has observed a dark matter signal consistent with their result. To address this puzzle, the COSINE-100 collaboration conducted a model-independent test using sodium iodide crystal detectors, the same target material as DAMA/LIBRA. Analyzing data collected over 6.4 years by the effective mass of 61.3 kg, with improved energy calibration and time-dependent background modeling, we found no evidence of an annual modulation signal, challenging the DAMA/LIBRA result with a confidence level greater than 3σ. This finding represents a substantial step toward resolving the long-standing debate surrounding DAMA/LIBRA’s dark matter claim, indicating that the observed modulation is unlikely to be caused by dark matter interactions.