A new measurement of Hf-174 alpha decay to the ground state of Yb-170 was performed deep underground at the Gran Sasso National Laboratory (LNGS) of the INFN (Italy). The experimental data were accumulated over 97.7 days with a 16.87 g Cs2HfCl6 single crystal. A new half-life value of Hf-174 alpha decay: T-1/2 = (3.8-0.9+1.7)x1016 yr, was evaluated. The total internal alpha activity of the crystal is 18.6(4) mBq/kg, and should be further improved, especially in terms of Sm-147 contamination (0.25 mBq/kg), in order to achieve a higher experimental sensitivity

A search for alpha and beta beta decays of naturally occurring osmium isotopes to the excited levels of daughter nuclei has been performed using an ultra-low-background broad-energy germanium gamma detector and an ultrapure osmium sample at the Gran Sasso National Laboratory of the INFN (Italy). The isotopic composition of the osmium sample has been measured with high precision by using negative thermal ionization mass spectrometry. During the data taking with the gamma detector, no effect has been detected, and lower limits for the half-life of alpha and beta beta decays were set at the level of 10(15) - 10(20) yr. In the case of a decays of Os-184 and Os-186 to the first excited levels of daughter nuclei, the limits substantially exceed the present theoretical estimates of the decays probabilities. This gives hope to the possibility to detect such transitions in the ongoing data taking. The present work will describe a review of recent new measurements and new experimental perspectives.

Abstract The $$2\nu 2\beta $$ 2 ν 2 β decay of $$^{150}\hbox {Nd}$$ 150 Nd to the first excited 740.5 keV $$0^{+}_{1}$$ 0 1 + level of $$^{150}\hbox {Sm}$$ 150 Sm was measured over 5.845 years with the help of a four-crystal low-background HPGe $$\gamma $$ γ spectrometry system in the underground low-background laboratory STELLA of LNGS-INFN. A 2.381 kg highly purified Nd-containing sample was employed as the decay source. The expected de-excitation gamma-quanta of the $$0^{+}_{1}$$ 0 1 + level with energies 334.0 keV and 406.5 keV were observed both in one-dimensional spectrum and in coincidence data resulting in the half-life $$T_{1/2}=[0.83^{+0.18}_{-0.13}\mathrm {(stat)}^{+0.16}_{-0.19}\mathrm {(syst)}]\times 10^{20}$$ T 1 / 2 = [ 0 . 83 - 0.13 + 0.18 ( stat ) - 0.19 + 0.16 ( syst ) ] × 10 20 year. Interpreting an excess of the 334.0-keV peak area as an indication of the $$2\beta $$ 2 β decay of $$^{150}\hbox {Nd}$$ 150 Nd to the 334.0 keV $$2^+_1$$ 2 1 + excited level of $$^{150}\hbox {Sm}$$ 150 Sm with a half-life of $$T_{1/2}=[1.5^{+2.3}_{-0.6}\mathrm {(stat)}\pm 0.4\mathrm {(syst)}]\times 10^{20}$$ T 1 / 2 = [ 1 . 5 - 0.6 + 2.3 ( stat ) ± 0.4 ( syst ) ] × 10 20 year, the $$2\nu 2\beta $$ 2 ν 2 β half-life of $$^{150}\hbox {Nd}$$ 150 Nd for the transition to the 0 $$^{+}_{1}$$ 1 + level is $$T_{1/2}=[1.03^{+0.35}_{-0.22}\mathrm {(stat)}^{+0.16}_{-0.19}\mathrm {(syst)}]\times 10^{20}$$ T 1 / 2 = [ 1 . 03 - 0.22 + 0.35 ( stat ) - 0.19 + 0.16 ( syst ) ] × 10 20 year, in agreement with the previous experiments. Both half-life values reasonably agree with the theoretical calculations in the framework of proton-neutron QRPA with isospin restoration combined with like nucleon QRPA for description of excited states in the final nuclei. For $$2\nu 2\beta $$ 2 ν 2 β and $$0\nu 2\beta $$ 0 ν 2 β transitions of $$^{150}\hbox {Nd}$$ 150 Nd and $$^{148}\hbox {Nd}$$ 148 Nd to several excited levels of $$^{150}\hbox {Sm}$$ 150 Sm and $$^{148}\hbox {Sm}$$ 148 Sm , limits were set at level of $$T_{1/2}>10^{20}-10^{21}$$ T 1 / 2 > 10 20 - 10 21 year.

The 2ν 2β decay of ^150Nd to the first excited 740.5 keV 0^+_1 level of ^150Sm was measured over 5.845 years with the help of a four-crystal low-background HPGe γ spectrometry system in the underground low-background laboratory STELLA of LNGS-INFN. A 2.381 kg highly purified Nd-containing sample was employed as the decay source. The expected de-excitation gamma-quanta of the 0^+_1 level with energies 334.0 keV and 406.5 keV were observed both in one-dimensional spectrum and in coincidence data resulting in the half-life T_1/2=[0.83^+0.18_-0.13(stat)^+0.16_-0.19(syst)]× 10^20 year. Interpreting an excess of the 334.0-keV peak area as an indication of the 2β decay of ^150Nd to the 334.0 keV 2^+_1 excited level of ^150Sm with a half-life of T_1/2=[1.5^+2.3_-0.6(stat)± 0.4(syst)]× 10^20 year, the 2ν 2β half-life of ^150Nd for the transition to the 0 ^+_1 level is T_1/2=[1.03^+0.35_-0.22(stat)^+0.16_-0.19(syst)]× 10^20 year, in agreement with the previous experiments. Both half-life values reasonably agree with the theoretical calculations in the framework of proton-neutron QRPA with isospin restoration combined with like nucleon QRPA for description of excited states in the final nuclei. For 2ν 2β and 0ν 2β transitions of ^150Nd and ^148Nd to several excited levels of ^150Sm and ^148Sm , limits were set at level of T_1/2>10^20-10^21 year.

Rare-event search experiments located on-surface, such as short-baseline reactor neutrino experiments, are often limited by muon-induced background events. Highly efficient muon vetos are essential to reduce the detector background and to reach the sensitivity goals. We demonstrate the feasibility of deploying organic plastic scintillators at sub-Kelvin temperatures. For the NUCLEUS experiment, we developed a cryogenic muon veto equipped with wavelength shifting fibers and a silicon photo multiplier operating inside a dilution refrigerator. The achievable compactness of cryostat-internal integration is a key factor in keeping the muon rate to a minimum while maximizing coverage. The thermal and light output properties of a plastic scintillation detector were examined. We report first data on the thermal conductivity and heat capacity of the polystyrene-based scintillator UPS-923A over a wide range of temperatures extending below one Kelvin. The light output was measured down to 0.8 K and observed to increase by a factor of 1.61 ± 0.05 compared to 300 K. The development of an organic plastic scintillation muon veto operating in sub-Kelvin temperature environments opens new perspectives for rare-event searches with cryogenic detectors at sites lacking substantial overburden.

A long-term measurement was conducted to search for α, double-α and double-β decays with γ quanta emission in naturally occurring osmium isotopes. This study took advantage of two ultra-low background HPGe detectors and one ultra-low background BEGe detector at the Gran Sasso National Laboratory (LNGS) of the INFN. Over almost 5 years of data were taken using high-purity osmium samples of approximately 173 g. The half-life limits set for α decays of 184Os to the first 2+ 103.6 keV excited level of 180W (T1/2 ≥ 9.3 × 1015 yr) and of 186Os to the first 2+ 100.1 keV of 182W (T1/2 ≥ 4.8 × 1017 yr) exceed substantially the present theoretical predictions that are at level of T1/2 (0.6–3) × 1015 yr for 184Os and T1/2 (0.3–2) × 1017 yr for 186Os. New half-life limits on the 2EC and ECβ+ decay of 184Os to the ground and excited levels of 184W were set at level of T1/2 > 1016–1017 yr; a lower limit on the 2β– decay of 192Os to the 2+ 316.5 keV excited level of 192Pt was estimated as T1/2 ≥ 6.1 × 1020 yr. The half-life limits for 2α decay of 189Os and 192Os were set for the first time at level of T1/2 > 1020 yr.

Any experiment aiming to measure rare events, like Coherent Elastic neutrino-Nucleus Scattering (CE NS) or hypothetical Dark Matter scattering, via nuclear recoils in cryogenic detectors relies crucially on a precise detector calibration at sub-keV energies. The Crab collaboration developed a new calibration technique based on the capture of thermal neutrons inside the target crystal. Together with the Nucleus experiment, first measurements with a moderated ^252 Cf neutron source and a cryogenic CaWO_4 detector were taken. We observed for the first time the 112eV peak caused by the ^182 W(n, ) ^183 W capture reaction and subsequent nuclear recoils. Currently, Crab is preparing a precision measurement campaign based on a monochromatic flux of thermal neutrons from the 250-kW Triga-mark II nuclear reactor at TU Wien. In this contribution, we introduce the Crab technique, present the first measurement of the 112eV peak, report the preparations for the precision measurement campaign, and give an outlook on the impact on the field of cryogenic detectors.

From 7 naturally occurring Nd isotopes, 5 are unstable in relation to α decay. If an excited level of the daughter nucleus is populated, or the daughter nucleus is unstable, γ quanta can be emitted. We used an ultra-low background spectrometry system with 4 high purity germanium (HPGe) detectors (about 225 cm3 volume each) to search for such decays using a highly purified Nd-containing sample with mass of 2.381 kg. Measurements were performed at the INFN Gran Sasso underground laboratory (with an overburden of about 3600 m w.e.) during 51,237 h. Half-life limits for α decays of 143Nd and 145Nd were determined to be T1/2(143Nd) > 1.1 × 1020 year and T1/2(145Nd) > 2.7 × 1019 year at 90

In this work, we present new studies by using different materials and procedures to improve the performances and radiopurity of Cs 2 ZrCl 6 (CZC) crystal scintillators. In particular, measurements of three new CZC crystals as scintillators were performed over 97.7 days live -time in the low -background DAMA/CRYS set-up deep underground at the Gran Sasso National Laboratory (LNGS) of the I.N.F.N. They allow us to derive elements for improvements towards a possible future use of this kind of detectors in the search for neutrino -less double beta decay of 94 , 96 Zr and rare single beta decay of 96 Zr.

DAMA/LIBRA is an experiment investigating the presence of Dark Matter particles in the Galactic halo. The target detectors are ultra-radiopure NaI(Tl) crystal scintillators. They are placed inside a low-background set-up at the underground Gran Sasso National Laboratory (LNGS) of the I.N.F.N.. DAMA/LIBRA has been in operation in two phases by pursuing the annual modulation as signature to point-out in a model-independent way the presence and the features of the Dark Matter (DM) signal in the counting rate. In its second phase of measurement, DAMA/LIBRA–phase2, it has been working with a lower software energy threshold with respect to DAMA/LIBRA–phase1. DAMA/LIBRA–phase2 confirms the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature, at 11.8 [Formula: see text] C.L. in the energy region (1–6) keV. In the energy region (2–6) keV, where data are also available from DAMA/NaI and DAMA/LIBRA–phase1, the achieved C.L. for the full exposure (2.86 ton × yr, 22 annual cycles) is 13.7 [Formula: see text]; the modulation amplitude of the single-hit scintillation events is: [Formula: see text] cpd/kg/keV, and the measured period and phase are well in agreement with those expected for DM particles. Detailed studies have excluded that the observed modulation is due to systematics or side reaction. In this proceedings the results achieved so far by the DAMA/LIBRA experiment and the new ones corresponding to two new annual cycles of data will be presented. Future perspectives of the experiment will be addressed.

The emission of $\gamma$-rays after a neutron capture in a cryogenic detector can generate mono-energetic nuclear recoils in the sub-keV regime, of direct interest for the calibration of Dark Matter and Coherent Elastic Neutrino Nucleus Scattering experiments. Here we show that accurate predictions of the nuclear recoil spectra induced by neutron captures require taking into account the interplay between the development in time of the de-excitation $\gamma$-cascade of the target nucleus and that of the associated atomic collisions in matter. We present detailed simulations coupling the FIFRELIN code for the description of the $\gamma$-cascades and the IRADINA code for the modelling of the fast atomic movements in matter. Nuclear recoil spectra are predicted, and made available to the community, for concrete cases of Al$_2$O$_3$, Si, Ge and CaWO$_4$ crystals exposed to a low intensity beam of thermal neutrons. We find that timing effects cause new calibration peaks to emerge in the recoil spectra and also impact the shape of the continuous recoil distribution. We discuss how they could give access to a rich physics program, spanning the accurate study of the response of cryogenic detectors in the sub-keV range, tests of solid state physics simulations and tests of nuclear models.

DAMA/LIBRA is an experiment investigating the presence of Dark Matter particles in the Galactic halo. The target detectors are ultra-radiopure NaI(Tl) crystal scintillators. They are placed inside a low-background set-up at the underground Gran Sasso National Laboratory (LNGS) of the I.N.F.N.. DAMA/LIBRA has been in operation in two phases by pursuing the annual modulation as signature to point-out in a model-independent way the presence and the features of the Dark Matter (DM) signal in the counting rate. In its second phase of measurement, DAMA/LIBRA–phase2, it has been working with a lower software energy threshold with respect to DAMA/LIBRA–phase1. DAMA/LIBRA–phase2 confirms the evidence of a signal that meets all the requirements of the model independent Dark Matter annual modulation signature, at 11.8 [Formula: see text] C.L. in the energy region (1–6) keV. In the energy region (2–6) keV, where data are also available from DAMA/NaI and DAMA/LIBRA–phase1, the achieved C.L. for the full exposure (2.86 ton × yr, 22 annual cycles) is 13.7 [Formula: see text]; the modulation amplitude of the single-hit scintillation events is: [Formula: see text] cpd/kg/keV, and the measured period and phase are well in agreement with those expected for DM particles. Detailed studies have excluded that the observed modulation is due to systematics or side reaction. In this proceedings the results achieved so far by the DAMA/LIBRA experiment and the new ones corresponding to two new annual cycles of data will be presented. Future perspectives of the experiment will be addressed.

Coherent elastic neutrino-nucleus scattering and low-mass dark matter detectors rely crucially on the understanding of their response to nuclear recoils. We report the first observation of a nuclear recoil peak at around 112 eV induced by neutron capture. The measurement was performed with a CaWO_{4} cryogenic detector from the NUCLEUS experiment exposed to a ^{252}Cf source placed in a compact moderator. We identify the expected peak structure from the single-γ de-excitation of ^{183}W with 3σ and its origin by neutron capture with 6σ significance. This result demonstrates a new method for precise, in situ, and nonintrusive calibration of low-threshold experiments.

An experiment to search for 2ε-, εβ+- and 2β+-decays of 106Cd, using a 215 g cadmium tungstate scintillation crystal enriched at 66 % by 106Cd (106CdWO4) is carried out at the Gran Sasso underground laboratory (Italy). Events in the 106CdWO4 detector are recorded in (anti)coincidences with two large-volume CdWO4 scintillation counters. The design of the detector system, calibration and background measurements, methods, and results of data analysis to determine key detector characteristics are described. The experimental data are compared with Monte Carlo simulation results, and a background model is constructed. The radioactive contamination of the setup components is studied. The sensitivity of the experiment approaches the level of theoretical predictions for the 2νεβ+-decay channel, while for other possible 2β-decay channels it is already on the level of lim T1/2 ∼ 1021-1022 years.

Recently, efforts on the building of Hf-based crystal scintillators have been performed. The so-called “source = detector” approach has been implemented to study rare nuclear processes in Hf isotopes with higher efficiency with respect to the HP-Ge spectrometry. In this work, a review of recent studies concerning rare nuclear processes in Hf isotopes are presented.

The NUCLEUS experiment aims to perform a high-precision measurement of Coherent Elastic Neutrino-Nucleus Scattering (CEvNS) at the EdF Chooz B nuclear power plant in France. CEvNS is a unique process to study neutrino properties and to search for physics beyond the Standard Model. The study of CEvNS is also important for light Dark-Matter searches. It could be a possible irreducible background for high-sensitivity Dark-Matter experiments. NUCLEUS is an experiment under construction based on ultra-low threshold (∼20 eV20eV_{nr}) cryogenic calorimeters, operated at tens-of-mK temperatures.