First Model Independent Results from DAMA/LIBRA–Phase2

Abstract

The first results obtained by the DAMA/LIBRA⁻phase2 experiment are presented. The data have been collected over six independent annual cycles corresponding to a total exposure of 1.13 ton × year, deep underground at the Gran Sasso National Laboratory. The DAMA/LIBRA⁻phase2 apparatus, about 250 kg highly radio-pure NaI(Tl), profits from a second generation high quantum efficiency photomultipliers and of new electronics with respect to DAMA/LIBRA⁻phase1. The improved experimental configuration has also allowed to lower the software energy threshold. The DAMA/LIBRA⁻phase2 data confirm the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature, at 9.5 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 (2.46 ton × year) is 12.9 σ .

Keywords

• dark matter
• low background NaI(Tl) scintillators
• model-independent annual modulation signature