The NEMO 3 detector, which has been operating in the Fréjus underground laboratory since February 2003, is devoted to the search for neutrinoless double-beta decay (beta beta 0v). The half-lives of ...the two neutrino double-beta decay (beta beta 2v) have been measured for 100Mo and 82Se. After 389 effective days of data collection from February 2003 until September 2004 (phase I), no evidence for neutrinoless double-beta decay was found from approximately 7 kg of 100Mo and approximately 1 kg of 82Se. The corresponding limits are T1/2(beta beta0v) > 4.6 x 10(23) yr for 100Mo and T1/2(beta beta 0v) > 1.0 x 10(23) yr for 82Se (90% C.L.). Depending on the nuclear matrix element calculation, the limits for the effective Majorana neutrino mass are < 0.7-2.8 e/v for 100Mo and < 1.7-4.9 eV for 82Se.
The double beta decay of
100Mo to the
0
1
+
and
2
1
+
excited states of
100Ru is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta ...decay of
100Mo to the excited
0
1
+
state is measured to be
T
1
/
2
(
2
ν
)
=
5.7
−0.9
+1.3
(
stat.
)
±
0.8
(
syst.
)
×
10
20
y
. The signal-to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited
0
1
+
state has been found. The corresponding half-life limit is
T
1
/
2
(
0
ν
)
(
0
+
→
0
1
+
)
>
8.9
×
10
22
y
(at 90% C.L.).
The search for the double beta decay to the
2
1
+
excited state has allowed the determination of limits on the half-life for the two neutrino mode
T
1
/
2
(
2
ν
)
(
0
+
→
2
1
+
)
>
1.1
×
10
21
y
(at 90% C.L.) and for the neutrinoless mode
T
1
/
2
(
0
ν
)
(
0
+
→
2
1
+
)
>
1.6
×
10
23
y
(at 90% C.L.).
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.
Using 9.4 g of
96Zr isotope and 1221 days of data from the NEMO-3 detector corresponding to 0.031 kg y, the obtained
2
ν
β
β
decay half-life measurement is
T
1
/
2
2
ν
=
2.35
±
0.14
(
stat
)
±
0.16
...(
syst
)
×
10
19
yr
. Different characteristics of the final state electrons have been studied, such as the energy sum, individual electron energy, and angular distribution. The 2
ν nuclear matrix element is extracted using the measured
2
ν
β
β
half-life and is
M
2
ν
=
0.049
±
0.002
. Constraints on
0
ν
β
β
decay have also been set.
We report results from the NEMO-3 experiment based on an exposure of 1275 days with 661 g of (130)Te in the form of enriched and natural tellurium foils. The ββ decay rate of (130)Te is found to be ...greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be T(½)(2ν) = 7.0 ± 0.9(stat) ± 1.1(syst) × 10(20) yr. This represents the most precise measurement of this half-life yet published and the first real-time observation of this decay.
Nucl.Phys.A781:209-226,2007 The double beta decay of 100Mo to the 0^+_1 and 2^+_1 excited states of 100Ru
is studied using the NEMO 3 data. After the analysis of 8024 h of data the
half-life for the ...two-neutrino double beta decay of 100Mo to the excited 0^+_1
state is measured to be T^(2nu)_1/2 = 5.7^{+1.3}_{-0.9}(stat)+/-0.8(syst)x
10^20 y. The signal-to-background ratio is equal to 3. Information about energy
and angular distributions of emitted electrons is also obtained. No evidence
for neutrinoless double beta decay to the excited 0^+_1 state has been found.
The corresponding half-life limit is T^(0nu)_1/2(0^+ --> 0^+_1) > 8.9 x 10^22 y
(at 90% C.L.).
The search for the double beta decay to the 2^+_1 excited state has allowed
the determination of limits on the half-life for the two neutrino mode
T^(2nu)_1/2(0^+ --> 2^+_1) > 1.1 x 10^21 y (at 90% C.L.) and for the
neutrinoless mode T^(0nu)_1/2(0^+ --> 2^+_1) > 1.6 x 10^23 y (at 90% C.L.).
Display omitted
•The paper presents original water absorption results for polyamide 6.6.•An important influence of water activity on water diffusion kinetic is observed when amorphous phase is in ...rubbery state.•The influence of water activity on diffusivity can be predicted based on physical consideration, i.e. the free volume theory.
Diffusion of water in polyamide 6.6 has been characterized for a wide range of temperatures (from 25 to 80°C) and various humidities using dynamic vapor sorption machine. The decrease in glass transition temperature (Tg) has also been measured using DMA tests. As usually observed, PA66 absorbs a large amount of water (up to 5% at 90%RH) with a Fickian behavior with a diffusion coefficient that depends on water activity for all temperatures. Moreover, it appears that the diffusion coefficient for tests performed below Tg is almost independent of the water activity whereas a strong dependency is observed above Tg. This behavior is to be compared to a large decrease of Tg with the absorption of water. The increase of the water diffusion can therefore be related to a change of the amorphous phase (the crystalline phase is supposed to absorb no water) from the glassy to the rubbery states. A model based on the free volume theory is used successfully to describe the wide experimental database. It is therefore possible to describe the dependency of the water diffusion kinetics on both temperature and water uptake using the approach described in this paper.
PDF
