Search

The results obtained with the total exposure of 1.04 ton × yr collected by DAMA/LIBRA–phase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. during 7 annual cycles are summarized. The DAMA/LIBRA–phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles) give evidence at 9.3 σ C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target. No systematic or side reaction able to mimic the exploited DM signature has been found or suggested by anyone over more than a decade. The same data of DAMA/LIBRA–phase1 have also been analyzed searching for possible DM second-order diurnal effect; at present, the DM diurnal modulation amplitude – expected because of the Earth diurnal motion – evaluated on the basis of the DAMA Dark Matter annual modulation results is below the reached experimental sensitivity. Some of the perspectives of the presently running DAMA/LIBRA–phase2 are outlined.

The DAMA/LIBRA experiment, running at the Gran Sasso National Labo- ratory of the I.N.F.N. in Italy, has a sensitive mass of about 250 kg highly radiopure NaI(Tl). It is mainly devoted to the investigation of Dark Matter (DM) particles in the Galactic halo by exploiting the model independent DM annual modulation signature. The present DAMA/LIBRA experiment and the former DAMA/NaI one (the first generation experiment having an exposed mass of about 100 kg) have released so far results cor- responding to a total exposure of 1.17 ton × yr over 13 annual cycles. They provide a model independent evidence of the presence of DM particles in the galactic halo at 8.9 σ C.L. on the basis of the investigated DM signature. The data of another annual cycle in the same DAMA/LIBRA running conditions are at hand. After the replacement at the end of 2012 of all the photomultipliers (PMTs) with new ones, having higher quantum efficiency, DAMA/LIBRA has entered to its phase 2; such a replacements allowed the lowering of the software energy threshold of the experiment in the present data taking. A short summary of the obtained results is presented and future perspectives of the experi- ment mentioned.

An experiment to search for double beta processes in 106Cd by using cadmium tungstate crystal scintillator enriched in 106Cd (106CdWO4) in coincidence with the four crystals HPGe detector GeMulti is in progress at the STELLA facility of the Gran Sasso underground laboratory of INFN (Italy). The 106CdWO4 scintillator is viewed by a low-background photomultiplier tube through a lead tungstate crystal light-guide produced from deeply purified archaeological lead to suppress gamma quanta from the photomultiplier tube. Here we report the first results of the experiment after 3233 hours of the data taking. A few new improved limits on double beta processes in 106Cd are obtained, in particular T1/2(2nuECb+) > 8.4e20 yr at 90% C.L.

Barium fluoride (BaF$_2$) crystal scintillators are promising detectors to search for double beta decay processes in $^{130}$Ba ($Q_{2{\beta}}$ = 2619(3) keV) and $^{132}$Ba ($Q_{2{\beta}}$ = 844(1) keV). The $^{130}$Ba isotope is of particular interest because of the indications on 2${\beta}$ decay found in two geochemical experiments. The radioactive contamination of BaF$_2$ scintillation crystal with mass of 1.714 kg was measured over 113.4 hours in a low-background DAMA/R&D set-up deep underground (3600 m w.e.) at the Gran Sasso National Laboratories of INFN (LNGS, Italy). The half-life of $^{212}$Po (present in the crystal scintillator due to contamination by radium) was estimated as $T_{1/2}$ = 298.8 $\pm$ 0.8(stat.) $\pm$ 1.4(syst.) ns by analysis of the events pulse profiles., Comment: Contribution to Proc. of Int. Workshop on Radiopure Scintillators RPSCINT 2013, 17-20.09.2013, Kyiv, Ukraine; to be published in EPJ Web of Conferences; 4 pages, 7 figure and 1 table

The DAMA project develops and uses new/improved low background scintil- lation detectors to investigate the Dark Matter (DM) particle component(s) in the galactic halo and rare processes deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N.. Here some highlights of DAMA/LIBRA (Large sodium Iodide Bulk for Rare processes) as a unique apparatus in direct DM investigation for its full sensitive mass, target material, intrinsic radio-purity, methodological approach and all the controls performed on the experimental parameters are outlined. The DAMA/LIBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles) have reached a model-independent evidence at 9.3 σ C.L. for the pres- ence of DM particles in the galactic halo exploiting the DM annual modulation signature with highly radio-pure NaI(Tl) target. Some of the perspectives of the presently run- ning DAMA/LIBRA-phase2 are summarised and the powerful tools offered by a model independent strategy of DM investigation are pointed out.

Radiopure ZnWO 4 crystal scintillators with mass (0.1–0.7 kg) have been developed and put inmeasurement in the Gran Sasso National Laboratories of the INFN to search for rare processes. The radioactive contamination of the crystals have been estimated and the double beta decay of zinc and tungsten isotopes was searched for, reaching a sensitivity at the level of 10 18 −10 21 yr; in addition a new half-life limit on alpha transition of 183 W to the metastable excited level of 179 Hf has also been obtained. The achieved radiopurity of the ZnWO 4 crystals make them very promising detectors for ββ decay investigations while their anisotropic features make them very interesting detectors to investigate dark matter particles directionality.

Cadmium tungstate crystal scintillators enriched in $^{116}$Cd to 82% ($^{116}$CdWO$_4$, total mass of $\approx$1.2 kg) are used to search for 2$\beta$ decay of $^{116}$Cd deep underground at the Gran Sasso National Laboratory of the INFN (Italy). The radioactive contamination of the $^{116}$CdWO$_4$ crystals has been studied carefully to reconstruct the background of the detector. The measured half-life of $^{116}$Cd relatively to 2$\nu$2$\beta$ decay is $T^{2\nu2\beta}_{1/2}$ = [2.8 $\pm$ 0.05(stat.) $\pm$ 0.4(syst.)] $\times$ 10$^{19}$ yr, in agreement with the results of previous experiments. The obtained limit on the 0$\nu$2$\beta$ decay of $^{116}$Cd (considering the data of the last 8696 h run with an advanced background 0.12(2) counts/yr/kg/keV in the energy interval 2.7-2.9 MeV) is $T_{1/2} \ge 1.0 \times 10^{23}$ yr at 90% C.L. The sensitivity of the experiment to the $0\nu2\beta$ process is $\lim T_{1/2} = 3 \times 10^{23}$ yr at 90% C.L. over 5 years of the measurements and it can be advanced (by further reduction of the background by a factor 3-30) to the level of $\lim T_{1/2} = (0.5-1.5) \times 10^{24}$ yr for the same period of the data taking., Comment: Contribution to Proc. of Int. Workshop on Radiopure Scintillators RPSCINT 2013, 17-20.09.2013, Kyiv, Ukraine; to be published in EPJ Web of Conferences; 4 pages, 1 figure and 3 tables

The results obtained with the total exposure of 1.04 ton × yr collected by DAMA/LIBRA–phase1 deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. during 7 annual cycles are briefly summarized. The DAMA/LIBRA–phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles) give evidence at 9.3 σ C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target. The modulation parameters are well 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 more than a decade. Some of the perspectives of the presently running DAMA/LIBRA–phase2 are outlined.