Limits and performances of a BaWO4 single crystal

A Barium Tungstate single crystal (BaWO4) was produced using the low thermal gradient Czochralski technique. In this paper the results concerning its light emission and radioactive contaminants are presented. The aim of this work is to investigate the possibility to realize BaWO4 crystals with suitably features to study the double beta decay of 130Ba and 132Ba isotopes by the “source=detector” approach. The results show the limitations of a BaWO4 crystal as a scintillator and give some idea on how to overcome them in order to take profit from the potentiality of this single crystal

New development of radiopure ZnWO4 crystal scintillators

The residual radioactive contaminations of zinc tungstate crystal scintillators, produced by low-thermal-gradient Czochralski technique in various conditions, have been measured in the DAMA/R&D; low background setup at the Gran Sasso National Laboratory (INFN, Italy). The total alpha activity has been measured in the detectors realized with different processes to vary between 158 and 1418 μ Bq/kg. The internal 228 Th contamination activity has been estimated as 0.34 μ Bq/kg in the most polluted crystal, while only upper limits for other ones have been set at level from < 0.17 μ Bq/kg to < 1.3 μ Bq/kg. These results open possibility for further radio-purifications of ZnWO 4 crystal scintillators, which are of potential interests in various fields

Aurora experiment: Final results of studies of 116Cd 2β decay with enriched 116CdWO4 crystal scintillators

Final results of studies of 116Cd 2β decay with CdWO4 crystal scintillators, enriched in 116Cd to 82%, are presented. After few years (2011 – 2017) of measurements with radiopure 116CdWO4 scintillators (mass of 1.162 kg) at the Gran Sasso underground laboratory (Italy), the half-life of 116Cd relatively to 2ν2β decay to the ground state of 116Sn was measured with the highest up-to-date accuracy as T1/2=(2.63+0.11−0.12)×10^19 yr. A new limit on 0ν2β decay of 116Cd was set as T1/2≥2.2×10^23 yr at 90% C.L., which is the most stringent to-date restriction for this isotope. Limits for 0ν2β decay with majoron(s) emission, Lorentz-violating 2ν2β decay and 2β transitions to excited states of 116Sn were set at the level of T1/2≥10^20−10^22 yr

Investigation of double beta decay of 116Cd with the help of enriched 116CdWO4 crystal scintillators

An experiment to search for 2β processes in 116Cd with the help of enriched (to 82%) cadmium tungstate crystal scintillators is in progress at the Gran Sasso National Laboratory of the INFN (LNGS, Italy). After 11074 h of data taking in the last configuration, the preliminary estimate for the half-life of 116Cd relatively to 2ν2β decay is T1/2 = [2.52 ± 0.02(stat.) ± 0.14(syst.)] × 10^19 yr. By using the data of previous stages of the experiment with a similar level of background (≈ 0.1 counts/(keV kg yr) in the energy interval 2.7 – 2.9 MeV; the total time of measurements is 19770 h) we have obtained a new limit on the 0ν2β decay of 116Cd to the ground state of 116Sn: T1/2 ≥ 1.9 × 10^23 yr at 90% C.L. New limits on different 2β processes in 116Cd (decays with majorons, transitions to the excited levels) are obtained on the level of T1/2 ≥ 10^20 – 10^22 yr

Recent Developments and Results on Double Beta Decays with Crystal Scintillators and HPGe Spectrometry

Recent developments, results, and perspectives arising from double beta decay experiments at the Gran Sasso National Laboratory (LNGS) of the INFN by using HPGe detectors and crystal scintillators and by exploiting various approaches and different isotopes are summarized. The measurements here presented have been performed in the experimental set-ups of the DAMA collaboration. These setups are optimized for low-background studies and operate deep underground at LNGS. The presented results are of significant value to the field, and the sensitivity achieved for some of the considered isotopes is one of the best available to date

LUMINEU: a search for neutrinoless double beta decay based on ZnMoO 4 scintillating bolometers

The LUMINEU is designed to investigate the possibility to search for neutrinoless double beta decay in 100Mo by means of a large array of scintillating bolometers based on ZnMoO4 crystals enriched in 100Mo. High energy resolution and relatively fast detectors, which are able to measure both the light and the heat generated upon the interaction of a particle in a crystal, are very promising for the recognition and rejection of background events. We present the LUMINEU concepts and the experimental results achieved aboveground and underground with large-mass natural and enriched crystals. The measured energy resolution, the α/β discrimination power and the radioactive internal contamination are all within the specifications for the projected final LUMINEU sensitivity. Simulations and preliminary results confirm that the LUMINEU technology can reach zero background in the region of interest (around 3 MeV) with exposures of the order of hundreds kgXyears, setting the bases for a next generation 0v2β decay experiment capable to explore the inverted hierarchy region of the neutrino mass pattern

Final results on the 0 νββ decay half-life limit of 100 Mo from the CUPID-Mo experiment

The CUPID-Mo experiment to search for 0νββ decay in 100Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator for CUPID, a next generation 0νββ decay experiment. CUPID-Mo was comprised of 20 enriched Li 2100MoO 4 scintillating calorimeters, each with a mass of ∼ 0.2 kg, operated at ∼ 20 mK. We present here the final analysis with the full exposure of CUPID-Mo (100Mo exposure of 1.47 kg × year) used to search for lepton number violation via 0νββ decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the 100Mo 0νββ decay half-life of T1/20ν> 1.8 × 10 24 year (stat. + syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of 〈 mββ〉 <(0.28-0.49) eV, dependent upon the nuclear matrix element utilized

New measurement of double-β decays of Mo100 to excited states of Ru100 with the CUPID-Mo experiment

The CUPID-Mo experiment, located at the Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20Li2Mo100O4 (LMO) calorimeters, each equipped with a Ge light detector for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double-β decays of Mo100 to the first 0+ and 2+ excited states of Ru100 using the full CUPID-Mo exposure (2.71kgyr of LMO). We measure the half-life of 2νββ decay to the 01+ state as T1/22ν→01+=(7.5±0.8(stat.)-0.3+0.4(syst.))×1020yr. The bolometric technique enables measurement of the electron energies as well as the γ rays from nuclear deexcitation and this allows us to set new limits on the two-neutrino decay to the 21+ state of T1/22ν→21+>4.4×1021yr(90% c.i.) and on the neutrinoless modes of T1/20ν→21+>2.1×1023yr(90% c.i.), T1/20ν→01+>1.2×1023yr(90% c.i.). Information on the electrons' spectral shape is obtained, which allows us to make the first comparison of the single and higher state dominance 2νββ decay models for the 01+ excited state of Ru100