We report the measurement of the two-neutrino double-beta ($2\nu\beta\beta$) decay of $^{100}$Mo to the ground state of $^{100}$Ru using lithium molybdate (\crystal) scintillating bolometers. The ...detectors were developed for the CUPID-Mo program and operated at the EDELWEISS-III low background facility in the Modane underground laboratory. From a total exposure of $42.235$ kg$\times$d, the half-life of $^{100}$Mo is determined to be $T_{1/2}^{2\nu}=7.12^{+0.18}_{-0.14}\,\mathrm{(stat.)}\pm0.10\,\mathrm{(syst.)}\times10^{18}$ years. This is the most accurate determination of the $2\nu\beta\beta$ half-life of $^{100}$Mo to date. We also confirm, with the statistical significance of $>3\sigma$, that the single-state dominance model of the $2\nu\beta\beta$ decay of $^{100}$Mo is favored over the high-state dominance model.
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
184
Os to the first 2
+
103.6 keV excited level of
180
W (
T
1/2
≥ 9.3 × 10
15
yr) and of
186
Os to the first 2
+
100.1 keV of
182
W (
T
1/2
≥ 4.8 × 10
17
yr) exceed substantially the present theoretical predictions that are at level of
T
1/2
~ (0.6–3) × 10
15
yr for
184
Os and
T
1/2
~ (0.3–2) × 10
17
yr for
186
Os. New half-life limits on the 2EC and ECβ
+
decay of
184
Os to the ground and excited levels of
184
W were set at level of
T
1/2
> 10
16
–10
17
yr; a lower limit on the 2β
–
decay of
192
Os to the 2
+
316.5 keV excited level of
192
Pt was estimated as
T
1/2
≥ 6.1 × 10
20
yr. The half-life limits for 2α decay of
189
Os and
192
Os were set for the first time at level of
T
1/2
> 10
20
yr.
A search for double-beta decay of
190
Pt and
198
Pt with emission of
γ
-ray quanta was realized at the HADES underground laboratory with a 148 g platinum sample measured by two ultralow-background ...HPGe detectors over 8946 h. The isotopic composition of the platinum sample has been measured with high precision using inductively coupled plasma mass spectrometry. New lower limits for the half-lives of
190
Pt relative to different channels and modes of the decays were set on the level of
lim
T
1
/
2
∼
10
14
–
10
16
year. A possible exact resonant
0
ν
K
N
transition to the 1,2 1326.9 keV level of
190
Os is limited for the first time as
T
1
/
2
≥
2.5
×
10
16
year. A new lower limit on the double-beta decay of
198
Pt to the first excited level of
198
Hg was set as
T
1
/
2
≥
3.2
×
10
19
year, one order of magnitude higher than the limit obtained in the previous experiment.
The resonance excitation of the 7Li nuclei in a LiF crystal with mass of 553 g by hypothetical axions emitted in the deexcitation of the 7Li nuclei in the Sun was searched for deep underground at the ...Gran Sasso National Laboratories (LNGS) of INFN (3600 m w.e.). The data collected with a low background HP Ge detector 244 cm3 during 4044h have allowed us to set the limit on the axion mass: ma<8.6 keV (90% C.L.) which is the best one for the 7Li solar axions to-date.
Anisotropic scintillators can offer a unique possibility to exploit the so-called directionality approach in order to investigate the presence of those Dark Matter (DM) candidates inducing nuclear ...recoils. In fact, their use can overcome the difficulty of detecting extremely short nuclear recoil traces. In this paper we present recent measurements performed on the anisotropic response of a
ZnWO
4
crystal scintillator to nuclear recoils, in the framework of the ADAMO project. The anisotropic features of the
ZnWO
4
crystal scintillators were initially measured with
α
particles; those results have been also confirmed by the additional measurements presented here. The experimental nuclear recoil data were obtained by using a neutron generator at ENEA-CASACCIA and neutron detectors to tag the scattered neutrons; in particular, the quenching factor values for nuclear recoils along different crystallographic axes have been determined for three different neutron scattering angles (i.e. nuclear recoils energies). From these measurements, the anisotropy of the light response for nuclear recoils in the
ZnWO
4
crystal scintillator has been determined at 5.4 standard deviations.
The first ever search for
α
decays to the first excited state in Yb was performed for six isotopes of hafnium (174, 176, 177, 178, 179, 180) using a high purity Hf sample of natural isotopic ...abundance with a mass of 179.8 g. For
179
Hf, also
α
decay to the ground state of
175
Yb was searched for thanks to the
β
-instability of the daughter nuclide
175
Yb. The measurements were conducted using an ultra-low-background HPGe-detector system located 225 m underground. After 75 days of data taking no decays were detected but lower bounds for the half-lives of the decays were derived on the level of
lim
T
1
/
2
∼
10
15
-
10
18
a. The decay with the shortest half-life based on theoretical calculation is the decay of
174
Hf to the first
2
+
84.3 keV excited level of
170
Yb. The experimental lower bound was found to be
T
1
/
2
≥
3.3
×
10
15
a.
Results are presented on our latest research, aimed at the development and study of oxide scintillation crystals (ZnWO 4 , ZnMoO 4 , PbWO 4 , PbMoO 4 , and MgWO 4 ) with high scintillation yield and ...low intrinsic radioactivity. We report on the improvement of these properties for conventional scintillators, as well as on new promising crystals based on metal tungstates and molybdates. The results are discussed in view of applying these materials in cryogenic experiments searching for dark matter and/or neutrinoless double beta decay.
The CUPID-Mo experiment to search for 0
ν
β
β
decay in
100
Mo 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 0
ν
β
β
decay experiment. CUPID-Mo was comprised of 20 enriched
Li
2
100
MoO
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 (
100
Mo exposure of 1.47
kg
×
year
) used to search for lepton number violation via 0
ν
β
β
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
100
Mo 0
ν
β
β
decay half-life of
T
1
/
2
0
ν
>
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
m
β
β
<
(
0.28
-
0.49
)
eV, dependent upon the nuclear matrix element utilized.
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.
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