Abstract The NEMO-3 results for the double- $$\beta $$ β decay of $$^{150}$$ 150 Nd to the 0 $$^+_1$$ 1 + and 2 $$^+_1$$ 1 + excited states of $$^{150}$$ 150 Sm are reported. The data recorded during ...5.25 year with 36.6 g of the isotope $$^{150}$$ 150 Nd are used in the analysis. The signal of the $$2\nu \beta \beta $$ 2 ν β β transition to the 0 $$^+_1$$ 1 + excited state is detected with a statistical significance exceeding 5 $$\sigma $$ σ . The half-life is measured to be $$T_{1/2}^{2\nu \beta \beta }(0^+_1) = \left 1.11 ^{+0.19}_{-0.14} \,\left( \hbox {stat}\right) ^{+0.17}_{-0.15}\,\left( \hbox {syst}\right) \right \times 10^{20}$$ T 1 / 2 2 ν β β ( 0 1 + ) = 1 . 11 - 0.14 + 0.19 stat - 0.15 + 0.17 syst × 10 20 year, which is the most precise value that has been measured to date. 90% confidence-level limits are set for the other decay modes. For the $$2\nu \beta \beta $$ 2 ν β β decay to the 2 $$^+_1$$ 1 + level the limit is $$T^{2\nu \beta \beta }_{1/2}(2^+_1) > 2.42 \times 10^{20}~\hbox {year}$$ T 1 / 2 2 ν β β ( 2 1 + ) > 2.42 × 10 20 year . The limits on the $$0\nu \beta \beta $$ 0 ν β β decay to the 0 $$^+_1$$ 1 + and 2 $$^+_1$$ 1 + levels of $$^{150}$$ 150 Sm are significantly improved to $$T_{1/2}^{0\nu \beta \beta }(0^+_1) > 1.36 \times 10^{22}~\hbox {year}$$ T 1 / 2 0 ν β β ( 0 1 + ) > 1.36 × 10 22 year and $$T_{1/2}^{0\nu \beta \beta }(2^+_1) > 1.26 \times 10^{22}~\hbox {year}$$ T 1 / 2 0 ν β β ( 2 1 + ) > 1.26 × 10 22 year .
Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (
2
ν
β
β
) half-life of
82
Se as
T
1
/
2
2
ν
=
9.39
±
0.17
stat
±
0.58
syst
×
10
19
y under the ...single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is
M
2
ν
=
0.0498
±
0.0016
. In addition, a search for neutrinoless double beta decay (
0
ν
β
β
) using 0.93 kg of
82
Se observed for a total of 5.25 y has been conducted and no evidence for a signal has been found. The resulting half-life limit of
T
1
/
2
0
ν
>
2.5
×
10
23
y
(
90
%
C.L.
)
for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of
⟨
m
ν
⟩
<
1.2
-
3.0
eV
, where the range reflects
0
ν
β
β
nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other
0
ν
β
β
mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.
The NEMO-2 tracking detector located in the Fréjus Underground Laboratory was designed as a prototype for the NEMO-3 detector and to study different modes of double beta decay. Measurements with
100
...Mo,
116
Cd,
82
Se and
96
Zr were carried out. Presented here are the experimental half-life limits on double beta decays for new Majoron emission modes and limits on effective neutrino–Majoron coupling constants.
Chemical purification of molybdenum samples for the NEMO 3 experiment Arnold, R.; Augier, C.; Baker, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
11/2001, Letnik:
474, Številka:
1
Journal Article
Recenzirano
Most currently, viable double beta decay experiments require highly enriched isotopic sources. These sources must be extraordinarily free of radioactive contamination. The double beta decay ...experiment NEMO 3 will study
100Mo, for which physical and chemical purification techniques have been investigated. The success of the chemical purification process is discussed in the context of ultra-low background, high-purity germanium spectrometer measurements.
Measurement of the background in the NEMO 3 double beta decay experiment Argyriades, J.; Arnold, R.; Augier, C. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
07/2009, Letnik:
606, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In the double beta decay experiment NEMO 3 a precise knowledge of the background in the signal region is of outstanding importance. This article presents the methods used in NEMO 3 to evaluate the ...backgrounds resulting from most if not all possible origins. It also illustrates the power of the combined tracking-calorimetry technique used in the experiment.
The NEMO-3 tracking detector is located in the Frejus Underground Laboratory. It was designed to study double beta decay in a number of different isotopes. Presented here are the experimental ...half-life limits on the double beta decay process for the isotopes 100Mo and 82Se for different Majoron emission modes and limits on the effective neutrino-Majoron coupling constants. In particular, new limits on "ordinary" Majoron (spectral index 1) decay of 100Mo T1/2 > 2.7cdot10 22 and 82Se T1/2 1.5cdot10 22) have been obtained. Corresponding bounds on the Majoron-neutrino coupling constant are g ee0.4-1.9 \cdot 10^{-4} and (0.66-1.7) \cdot 10 -4.
Possible background reductions in double beta decay experiments Arnold, R.; Augier, C.; Baker, J. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2003, Letnik:
503, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The background induced by radioactive impurities of
208
Tl
and
214
Bi
in the source of the double beta experiment NEMO-3 has been investigated. New methods of data analysis which decrease the ...background from the above-mentioned contamination are identified. The techniques can also be applied to other double beta decay experiments capable of measuring independently the energies of the two electrons.
Double beta decay of 100Mo to the excited states of daughter nuclei has been studied using a 600 cm3 low-background HPGe detector and an external source consisting of 2588 g of 97.5% enriched ...metallic 100Mo, which was formerly inside the NEMO-3 detector and used for the NEMO-3 measurements of 100Mo. The half-life for the two-neutrino double beta decay of 100Mo to the excited 01+ state in 100Ru is measured to be T1/2=7.5±0.6(stat)±0.6(syst)⋅1020 yr. For other (0ν+2ν) transitions to the 21+, 22+, 02+, 23+ and 03+ levels in 100Ru, limits are obtained at the level of ∼(0.25–1.1)⋅1022 yr.
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