First model independent results from DAMA/LIBRA-phase2.
Bernabei R., Belli P., Bussolotti A., Cappella F., Caracciolo V., Cerulli R., Dai C.J., D'Angelo A., Di Marco A., He H.L., Incicchitti A., Ma X.H., Mattei A., Merlo V., Montecchia F., Sheng X.D., Ye Z.P.
III - Astrofisica
Aula 32B-3 - Venerdì 21 h 15:30 - 18:30
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The first model-independent results obtained by the DAMA/LIBRA-phase2 experiment are presented. The data have been collected over 6 annual cycles corresponding to a total exposure of 1.13 ton $\times$ yr, deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. The DAMA/LIBRA-phase2 apparatus, $\simeq$ 250 kg highly radio-pure NaI(Tl), profits of a second generation high quantum efficiency photomultipliers and of new electronics with respect to DAMA/LIBRA-phase1. The improved experimental configuration has also allowed lowering the software energy threshold. New data analysis strategies are presented. The DAMA/LIBRA-phase2 data confirm the evidence for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature, at 9.5 $\sigma$ 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 (cumulative exposure 1.33 ton $\times$ yr, corresponding to 14 annual cycles), the achieved C.L. for the full exposure (2.46 ton $\times$ yr) is 12.9 $\sigma,$ the modulation amplitude of the single hit scintillation events is: (0.0103 $\pm$ 0.0008) cpd/kg/keV, the measured phase is (145$\pm$5) days and the measured period is (0.999$\pm$0.001) yr. All these values are good in agreement with those expected for DM particles. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over some decades.