New and recent results, and perspectives from DAMA/LIBRA–phase2

Here the results obtained by analysing other two annual cycles of DAMA/LIBRA– phase2 are presented and the long-standing model-independent annual modulation effect measured by DAMA deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. with different experimental configurations is summarized. In particular, profiting from a second generation high quantum efficiency photomultipliers and new electronics, the DAMA/LIBRA–phase2 apparatus (≃ 250 kg highly radio-pure NaI(Tl)) has allowed the reaching of lower software energy threshold. Including the results of the two new annual cycles, the total exposure of DAMA/LIBRA–phase2 over 8 annual cycles is 1.53 ton × yr. The evidence of a signal that meets all the requirements of the model independent Dark Matter (DM) annual modulation signature is further confirmed: 11.8 σ C.L. in the energy region (1–6) keV. In the energy region between 2 and 6 keV, where data are also available from DAMA/NaI and DAMA/LIBRA–phase1, the achieved C.L. for the full exposure (2.86 ton × yr) is 13.7 σ; the modulation amplitude of the single-hit scintillation events is: (0.01014±0.00074) cpd/kg/keV, the measured phase is (142.4±4.2) days and the measured period is (0.99834 ± 0.00067) yr, values all well in agreement with those expected for DM particles. No systematics or side reaction able to mimic the exploited DM signature (i.e. to account for the whole measured modulation amplitude and to simultaneously satisfy all the requirements of the signature) has been found or suggested by anyone throughout some decades thus far.