[en] The first search for double electron capture (2ε) and electron capture with positron emission (εβ ⁺) of ¹⁶²Er to the ground state and to several excited levels of ¹⁶²Dy was realized with 326 g of highly purified erbium oxide. The sample was measured over 1934 h by the ultra-low background HP Ge γ spectrometer GeCris (465 cm³) at the Gran Sasso underground laboratory. No effect was observed, the half-life limits were estimated at the level of $\mathrm{l}\mathrm{i}\mathrm{m}{T}_{1/2}\sim <!--\; ???\; -->{10}^{15}\text{--}{10}^{18}$ yr. A possible resonant 0ν KL ₁ capture in ¹⁶²Er to the 2⁺ 1 782.7 keV excited state of ¹⁶²Dy is restricted as T _1/2 ≥ 5.0 × 10¹⁷ yr at 90% C.L. A new improved half-life limit T _1/2 ≥ 4.1 × 10¹⁷ yr was set on the 2β ⁻ decay of ¹⁷⁰Er to the 2⁺ 84.3 keV first excited state of ¹⁷⁰Yb. (paper)

[en] The LUMTNEU program aims at performing a pilot experiment on 0ν2β decay of "1"0"0Mo using radiopure ZnMoO_4 crystals enriched in "1"0"0Mo operated as cryogenic scintillating bolometers. Large volume ZnMoO_4 crystal scintillators (∼ 0.3 kg) were developed and tested showing high performance in terms of radiopurity, energy resolution and α/β particle discrimination capability. Zinc molybdate crystal scintillators enriched in "1"0"0Mo were grown for the first time by the low-thermal-gradient Czochralski technique with a high crystal yield and an acceptable level of enriched molybdenum irrecoverable losses. A background level of ∼ 0.5 counts/(yr keV ton) in the region of interest can be reached in a large detector array thanks to the excellent detectors radiopurity and particle discrimination capability, suppression of randomly coinciding events by pulse-shape analysis, and anticoincidence cut. These results pave the way to future sensitive searches based on the LUMTNEU technology, capable of approachingand exploring the inverted hierarchy region of the neutrino mass pattern

[en] An experiment to measure the 2β ^– decay of ¹⁵⁰Nd to excited levels of ¹⁵⁰Sm using a highly purified 2.381 kg sample of Nd₂O₃ is in progress in the low-background set-up with 4 HPGe detectors (∼225 cm³ volume each). The detector is located deep underground (3600 m w.e.) at the STELLA facility of the Gran Sasso National Laboratory (LNGS) of the INFN (Italy). Two γ quanta with energies 334.0 keV and 406.5 keV emitted after deexcitation of the 0₁ ⁺ excited level of ¹⁵⁰Sm have been observed in the experimental data accumulated over 39898 h. The preliminary half-life value for 2β ^– decay of ¹⁵⁰Nd to the first 0⁺ excited level in ¹⁵⁰Sm (after the exposure of 10.8 kg × yr) was estimated as $T_{1/2}=[{9.7}_{-<!--\; ???\; -->1.9}^{+2.9}\left(\mathrm{s}\mathrm{t}\mathrm{a}\mathrm{t}.\right)\pm <!--\; ??\; -->1.5\left(\mathrm{s}\mathrm{y}\mathrm{s}\mathrm{t}.\right)]\times <!--\; ??\; -->{10}^{19}$ yr. The experiment is under data taking with the aim to improve the statistical uncertainties. (paper)

[en] A search for double beta decay of ^64,70Zn, ^180,186W was carried out by using low background ZnWO₄ crystal scintillators, while a CeCl₃ scintillation detector was applied to investigate 2β processes in ^136,138,142Ce. A search for 2β decay of ^96,104Ru, ^156,158Dy, ^190,198Pt and study of 2ν2β decay of ¹⁰⁰Mo to the first excited 0⁺ level of ¹⁰⁰Ru were realized by ultra-low background HPGe γ spectrometry. Moreover, CdWO₄ crystal scintillators from enriched ¹⁰⁶Cd and ¹¹⁶Cd isotopes were developed to search for 2β decay of ¹⁰⁶Cd and ¹¹⁶Cd. Finally, experiments aimed to investigate ^96,104Ru and ¹¹⁶Cd are in progress and a new phase of the experiment to search for 2β processes in ¹⁰⁶Cd is in preparation.

[en] A search for double β processes in ¹⁰⁶Cd was carried out at the Gran Sasso National Laboratories of the INFN, Italy; by using a CdWC₄ crystal scintillator (mass of 215 g) enriched in ¹⁰⁶Cd up to 66%. After 6590 h of data taking, half-life limits on double beta processes in ¹⁰⁶Cd were set at level of 10¹⁹ – 10²¹ yr. A possible resonant enhancement of the 0ν2ε processes has also been estimated in the framework of the QRPA approach.

[en] Sample of ¹⁰⁰MoO₃ with molybdenum enriched in ¹⁰⁰Mo to 99.5% and mass of 1199 g was measured deep underground (3600 m w.e.) in the Laboratori Nazionali del Gran Sasso of INFN, Italy; during 17249 h with a low-background set-up with 4 HP Ge detectors. After 2β2ν decay of ¹⁰⁰Mo to the 0⁺₁ excited level of ¹⁰⁰Ru (E_exc = 1131 keV), two γ quanta of 540 keV and 591 keV should be emitted in deexcitation process. Both these γ's are observed in the accumulated data as in coincidence spectrum as well in 1-dimensional sum spectrum. Measured half life is T_1/2 (7.0^+1.1_-0.8) x 10²⁰ yr, in agreement with positive results obtained in previous experiments.

[en] Several experiments were performed during last years at underground (3600 m w.e.) Laboratori Nazionali del Gran Sasso (LNGS) of the INFN, Italy; to search for resonant 2ε0ν captures in ⁹⁶Ru, ¹⁰⁶Cd, ¹³⁶Ce, ¹⁵⁶Dy, ¹⁵⁸Dy, ¹⁸⁰W, ¹⁸⁴Os, ¹⁹⁰Pt with the help of HP Ge semiconductor detectors, and ZnWO₄ and ¹⁰⁶CdWO₄ crystal scintillators. No evidence for r-2ε0ν decays was found, and only T_1/2 limits were established in the range of 10¹⁴ - 10²¹ yr.

[en] A cadmium tungstate crystal boule enriched in ¹¹⁶Cd to 82% with mass of 1868 g was grown by the low-thermal-gradient Czochralski technique. The isotopic composition of cadmium and the trace contamination of the crystal were estimated by High Resolution Inductively Coupled Plasma Mass-Spectrometry. The crystal scintillators produced from the boule were subjected to characterization that included measurements of transmittance and energy resolution. A low background scintillation detector with two ¹¹⁶CdWO₄ crystal scintillators (586 g and 589 g) was developed. The detector was running over 1727 h deep underground at the Gran Sasso National Laboratories of the INFN (Italy), which allowed to estimate the radioactive contamination of the enriched crystal scintillators. The radiopurity of a third ¹¹⁶CdWO₄ sample (326 g) was tested with the help of ultra-low background high purity germanium γ detector. Monte Carlo simulations of double β processes in ¹¹⁶Cd were used to estimate the sensitivity of an experiment to search for double β decay of ¹¹⁶Cd.

[en] An experiment to search for 2b processes in ¹⁰⁶Cd with the help of ¹⁰⁶CdWO₄ crystal scintillator (mass of 215 g), enriched in ¹⁰⁶Cd up to 66%, is in progress at the Gran Sasso National Laboratories of the INFN (Italy). After 1320 h of data taking, limits on double beta processes in ¹⁰⁶Cd have been established on the level of 10¹⁹-10²⁰ yr, in particular (all the results at 90% C.L.): T_1/2(0ν2ε)>3.6x10²⁰ yr, T_1/2(2νεβ⁺)>7.2x10¹⁹ yr, and T_1/2(2ν2β⁺)>2.5x10²⁰ yr. Resonant 0ν2ε processes have been restricted as T_1/2(0ν2K)>1.4x10²⁰ yr and T_1/2(0νLK)>3.2x10²⁰ yr. A possible resonant enhancement of the 0ν2ε processes is estimated in the framework of the QRPA approach.

[en] AMoRE (Advanced Mo based Rare process Experiment) collaboration is going to use calcium molybdate crystals as cryogenic scintillation detector in a search for neutrinoless DBD of ¹⁰⁰Mo isotope. Simultaneous detection of phonons and light will be used to reject internal background. A FWHM resolution of 0.2% in the phonon channel has been achieved with a 0.5 cm³ crystal. Several ⁴⁰Ca¹⁰⁰MoO₄ crystals (≈ 0.5 kg) have been developed from enriched ¹⁰⁰Mo and depleted ⁴⁰Ca materials. The light yield of these crystals has been shown to be comparable with reference CaMoO₄ scintillators for temperatures ranging down to 8 K. The content of dangerous radioisotopes in the crystals is under measurement. The projected sensitivity of the experiment for a 250 kg × years exposure is lim T_1/2 ∼ 3 × 10²⁶ years, which corresponds to the effective Majorana neutrino mass (m_v) ∼ 0.02 – 0.06 eV.