The NEMO-3 results for the double-$\beta$ decay of $^{150}$Nd to the 0$^+_1$
and 2$^+_1$ excited states of $^{150}$Sm are reported. The data recorded during
5.25 yr with 36.6 g of the isotope ...$^{150}$Nd are used in the analysis. For the
first time, the signal of the $2\nu\beta\beta$ transition to the 0$^+_1$
excited state is detected with a statistical significance exceeding 5$\sigma$.
The half-life is measured to be $T_{1/2}^{2\nu\beta\beta}(0^+_1) = \left 1.11
^{+0.19}_{-0.14} \,\left(\mbox{stat}\right) ^{+0.17}_{-0.15}\,
\left(\mbox{syst}\right) \right \times10^{20}\,\mbox{yr}$. The limits are set
on the $2\nu\beta\beta$ decay to the 2$^+_1$ level and on the $0\nu\beta\beta$
decay to the 0$^+_1$ and 2$^+_1$ levels of $^{150}$Sm.
The discovery of scintillation in the blue regime from polyethylene naphthalate (PEN), a commonly used high-performance industrial polyester plastic, has sparked considerable interest from the ...physics community as a new type of plastic scintillator material. This observation in addition to its good mechanical and radiopurity properties makes PEN an attractive candidate as an active structure scintillator for low-background physics experiments. This paper reports on investigations of its potential in terms of production tests of custom made tiles and various scintillation light output measurements. These investigations substantiate the high potential of usage of PEN in low-background experiments.
The SuperNEMO experiment will search for neutrinoless double-beta decay (\(0\nu\beta\beta\)), and study the Standard-Model double-beta decay process (\(2\nu\beta\beta\)). The SuperNEMO technology can ...measure the energy of each of the electrons produced in a double-beta (\(\beta\beta\)) decay, and can reconstruct the topology of their individual tracks. The study of the double-beta decay spectrum requires very accurate energy calibration to be carried out periodically. The SuperNEMO Demonstrator Module will be calibrated using 42 calibration sources, each consisting of a droplet of \(^{207}\)Bi within a frame assembly. The quality of these sources, which depends upon the entire \(^{207}\)Bi droplet being contained within the frame, is key for correctly calibrating SuperNEMO's energy response. In this paper, we present a novel method for precisely measuring the exact geometry of the deposition of \(^{207}\)Bi droplets within the frames, using Timepix pixel detectors. We studied 49 different sources and selected 42 high-quality sources with the most central source positioning.
Double-beta decays of \(^{100}\)Mo from the 6.0195-year exposure of a 6.914 kg high-purity sample were recorded by the NEMO-3 experiment that searched for neutrinoless double-beta decays. These ...ultra-rare transitions to \(^{100}\)Ru have a half-life of approximately \(7\times10^{18}\) years, and have been used to conduct the first ever search for periodic variations of this decay mode. The Lomb-Scargle periodogram technique, and its error-weighted extension, were employed to look for periodic modulations of the half-life. Monte Carlo modeling was used to study the modulation sensitivity of the data over a broad range of amplitudes and frequencies. Data show no evidence of modulations with amplitude greater than 2.5% in the frequency range of \(0.33225\,{\rm y^{-1}}\) to \(365.25\,{\rm y^{-1}}\).
The NEMO-3 results for the double-\(\beta\) decay of \(^{150}\)Nd to the 0\(^+_1\) and 2\(^+_1\) excited states of \(^{150}\)Sm are reported. The data recorded during 5.25 yr with 36.6 g of the ...isotope \(^{150}\)Nd are used in the analysis. For the first time, the signal of the \(2\nu\beta\beta\) transition to the 0\(^+_1\) excited state is detected with a statistical significance exceeding 5\(\sigma\). The half-life is measured to be \(T_{1/2}^{2\nu\beta\beta}(0^+_1) = \left 1.11 ^{+0.19}_{-0.14} \,\left(\mbox{stat}\right) ^{+0.17}_{-0.15}\, \left(\mbox{syst}\right) \right \times10^{20}\,\mbox{yr}\). The limits are set on the \(2\nu\beta\beta\) decay to the 2\(^+_1\) level and on the \(0\nu\beta\beta\) decay to the 0\(^+_1\) and 2\(^+_1\) levels of \(^{150}\)Sm.
A new experiment devoted to searches for double electron capture in Cd-106 decay is being performed at the Modane underground laboratory (4800 mwe) with the 32-detector TGV-2 spectrometer. The limit ...T (1/2)(2 nu EC/EC) > 2.0x10(20) yr at a 90%confidence level (C.L.) was obtained from a preliminary analysis of data obtained over 2250 h of measurements with about 23.2 g sample enriched in the isotope Cd-106 to 99.57%. The limits T (1/2)(KL, 2741 keV) > 0.9 x 10(20) yr and T (1/2)(KK, 2718 keV) a parts per thousand << 1.4 x 10(20) yr at a 90% C.L. on the neutrinoless decay of Cd-106 were obtained from measurements performed with the Obelix low-background spectrometer from high-purity germanium (HPGe spectrometer) for a sample of mass about 23.2 g enriched in the isotope Cd-106.
The full data set of the NEMO-3 experiment has been used to measure the half-life of the two-neutrino double beta decay of \(^{100}\)Mo to the ground state of \(^{100}\)Ru, \(T_{1/2} = \left 6.81 \pm ...0.01\,\left(\mbox{stat}\right) ^{+0.38}_{-0.40}\,\left(\mbox{syst}\right) \right \times10^{18}\) y. The two-electron energy sum, single electron energy spectra and distribution of the angle between the electrons are presented with an unprecedented statistics of \(5\times10^5\) events and a signal-to-background ratio of ~80. Clear evidence for the Single State Dominance model is found for this nuclear transition. Limits on Majoron emitting neutrinoless double beta decay modes with spectral indices of n=2,3,7, as well as constraints on Lorentz invariance violation and on the bosonic neutrino contribution to the two-neutrino double beta decay mode are obtained.
A new experiment devoted to searches for double electron capture in
106
Cd decay is being performed at the Modane underground laboratory (4800 mwe) with the 32-detector TGV-2 spectrometer. The limit
...T
1/2
(2
ν
EC/EC) > 2.0×10
20
yr at a 90%confidence level (C.L.) was obtained from a preliminary analysis of data obtained over 2250 h of measurements with about 23.2 g sample enriched in the isotope
106
Cd to 99.57%. The limits
T
1/2
(KL, 2741 keV) > 0.9 × 10
20
yr and
T
1/2
(KK, 2718 keV) ≫ 1.4 × 10
20
yr at a 90% C.L. on the neutrinoless decay of
106
Cd were obtained from measurements performed with the Obelix low-background spectrometer from high-purity germanium (HPGe spectrometer) for a sample of mass about 23.2 g enriched in the isotope
106
Cd.
Using data from the NEMO-3 experiment, we have measured the two-neutrino
double beta decay ($2\nu\beta\beta$) half-life of $^{82}$Se as $T_{1/2}^{2\nu}
= \left 9.39 \pm 0.17\,\left(\mbox{stat}\right) ...\pm
0.58\,\left(\mbox{syst}\right)\right \times 10^{19}$ y under the single-state
dominance hypothesis for this nuclear transition. The corresponding nuclear
matrix element is $\left|M^{2\nu}\right| = 0.0498 \pm 0.0016$. In addition, a
search for neutrinoless double beta decay ($0\nu\beta\beta$) 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 $T_{1/2}^{0\nu} > 2.5
\times 10^{23} \,\mbox{y} \,(90\%\,\mbox{C.L.})$ for the light neutrino
exchange mechanism leads to a constraint on the effective Majorana neutrino
mass of $\langle m_{\nu} \rangle < \left(1.2 - 3.0\right) \,\mbox{eV}$, where
the range reflects $0\nu\beta\beta$ nuclear matrix element values from
different calculations. Furthermore, constraints on lepton number violating
parameters for other $0\nu\beta\beta$ mechanisms, such as right-handed
currents, majoron emission and R-parity violating supersymmetry modes have been
set.
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