Model-independent results from DAMA/LIBRA-phase2-empowered

The DAMA/LIBRA-phase2 experiment was upgraded in 2021 to enhance its sensitivity by lowering the software energy threshold while maintaining a large efficiency. The new configuration, referred to as DAMA/LIBRA-phase2-empowered, collected data for three years. This study extends the investigation of the long-standing, model-independent annual modulation effect pointed out by the DAMA highly radiopure NaI(Tl) experimental setups at the Gran Sasso National Laboratory of the National Institute for Nuclear Physics, using different experimental configurations. The software energy threshold of DAMA/LIBRA-phase2-empowered is below 1 keV, and the exposure is 0.541 t⋅yr. Adding these new results to the previously released DAMA/LIBRA-phase2, the exposure is 2.07 t⋅yr over 11 independent annual cycles, yielding evidence for a signal that fulfills all the requirements of the model-independent Dark Matter annual modulation signature at a confidence level of 13.9 σ in the 1–6 keV energy region. In the 2–6 keV interval, where data from DAMA/NaI and DAMA/LIBRA-phase1 are also available, the combined exposure reaches 3.40 t⋅yr, corresponding to a confidence level of 15.3 σ. No systematic effect or side process capable of simultaneously satisfying all the distinctive features of the exploited Dark Matter annual modulation signature and accounting for the observed modulation amplitude is available.