Combined Annual Modulation Dark Matter Search with COSINE-100 and ANAIS-112

The annual modulation signal, claimed to be consistent with dark matter as observed by DAMA/LIBRA in a sodium-iodide based detector, has persisted for over two decades. COSINE-100 and ANAIS-112 were designed to test the claim directly using the same target material. COSINE-100, located at Yangyang Underground Laboratory in South Korea, and ANAIS-112, located at Canfranc Underground Laboratory in Spain, have been taking data since 2016 and 2017, respectively. Each experiment published its respective results independently. In this Letter, we present the results of an annual modulation search as a test of the signal observed by DAMA/LIBRA with the first three respective years of data from COSINE-100 and ANAIS-112. Using a Markov Chain Monte Carlo method, we find best fit values for modulation amplitude of -0.0002±0.0026 cpd/kg/keV in the 1-6 keV and 0.0021±0.0028 cpd/kg/keV in the 2-6 keV energy regions. These results are not compatible with DAMA/LIBRA's assertion for their observation of annual modulation at 3.7σ and 2.6σ, respectively. Performing a simple combination of the newly released 6-year datasets from both experiments finds values consistent with no modulation at 0.0005±0.0019 cpd/kg/keV in the 1-6 keV and 0.0027±0.0021 cpd/kg/keV in the 2-6 keV energy regions with 4.7σ and 3.5σ respective exclusions of the DAMA/LIBRA signal.