The NEMO-3 experiment measured the half-life of the 2νββ decay and searched for the 0νββ decay of Cd116. Using 410 g of Cd116 installed in the detector with an exposure of 5.26 y, (4968±74) events ...corresponding to the 2νββ decay of Cd116 to the ground state of Sn116 have been observed with a signal to background ratio of about 12. The half-life of the 2νββ decay has been measured to be T1/22ν=2.74±0.04(stat)±0.18(syst)×1019 y. No events have been observed above the expected background while searching for 0νββ decay. The corresponding limit on the half-life is determined to be T1/20ν≥1.0×1023 y at the 90% C.L. which corresponds to an upper limit on the effective Majorana neutrino mass of ⟨mν⟩≤1.4–2.5 eV depending on the nuclear matrix elements considered. Limits on other mechanisms generating 0νββ decay such as the exchange of R-parity violating supersymmetric particles, right-handed currents and majoron emission are also obtained.
The BiPo-3 detector Loaiza, P.; Barabash, A.S.; Basharina-Freshville, A. ...
Applied radiation and isotopes,
05/2017, Letnik:
123
Journal Article
Recenzirano
The BiPo-3 detector is a low radioactive detector dedicated to measuring ultra-low natural contaminations of 208Tl and 214Bi in thin materials, initially developed to measure the radiopurity of the ...double β decay source foils of the SuperNEMO experiment at the μBq/kg level. The BiPo-3 technique consists in installing the foil of interest between two thin ultra-radiopure scintillators coupled to low radioactive photomultipliers. The design and performances of the detector are presented.
In this paper, the final results of the 208Tl and 214Bi activity measurements of the first enriched 82Se foils are reported for the first time, showing the capability of the detector to reach sensitivities in the range of some μBq/kg.
•BiPo3 : low radioactive detector to measure ultra-low levels of 208Tl and 214Bi.•Backgrounds characterized.•Surface background : A(208Tl) =(0.9±0.2)μBq/m2 and A(214Bi) =(1.0±0.3)μBq/m2.•First SuperNemo double β source foils measured : A(208Tl) =(21±11)μBq/kg and A(214Bi) < 290μBq/kg at 90% C.L.•Shows capability to measure 208Tl in the range of some μBq/kg.
Abstract Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ($$2\nu \beta \beta $$ 2νββ ) half-life of $$^{82}$$ 82 Se as $$T_{\smash {1/2}}^{2\nu } \!=\! ...\left 9.39 \pm 0.17\left( \text{ stat }\right) \pm 0.58\left( \text{ syst }\right) \right \times 10^{19}$$ T1/22ν=9.39±0.17stat±0.58syst×1019 y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is $$\left| M^{2\nu }\right| = 0.0498 \pm 0.0016$$ M2ν=0.0498±0.0016 . In addition, a search for neutrinoless double beta decay ($$0\nu \beta \beta $$ 0νββ ) using 0.93 kg of $$^{82}$$ 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 $$T_{1/2}^{0\nu } > 2.5 \times 10^{23} \,\text{ y } \,(90\%\,\text{ C.L. })$$ T1/20ν>2.5×1023y(90%C.L.) for the light neutrino exchange mechanism leads to a constraint on the effective Majorana neutrino mass of $$\langle m_{\nu } \rangle < \left( 1.2{-}3.0\right) \,\text{ eV }$$ ⟨mν⟩<1.2-3.0eV , where the range reflects $$0\nu \beta \beta $$ 0νββ nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other $$0\nu \beta \beta $$ 0νββ mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.
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 double-beta decay of 82Se to the 0+1 excited state of 82Kr has been studied with the NEMO-3 detector using 0.93 kg of enriched 82Se measured for 4.75 y, corresponding to an exposure of 4.42 kg y. ...A dedicated analysis to reconstruct the gamma-rays has been performed to search for events in the 2e2g channel. No evidence of a 2nbb decay to the 0+1 state has been observed and a limit of T2n 1/2(82Se; 0+gs -> 0+1) > 1.3 1021 y at 90% CL has been set. Concerning the 0nbb decay to the 0+1 state, a limit for this decay has been obtained with T0n 1/2(82Se; 0+g s -> 0+1) > 2.3 1022 y at 90% CL, independently from the 2nbb decay process. These results are obtained for the first time with a tracko-calo detector, reconstructing every particle in the final state.
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.
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.
SuperNEMO is a double-\(\beta\) decay experiment, which will employ the successful tracker-calorimeter technique used in the recently completed NEMO-3 experiment. SuperNEMO will implement 100 kg of ...double-\(\beta\) decay isotope, reaching a sensitivity to the neutrinoless double-\(\beta\) decay (\(0\nu\beta\beta\)) half-life of the order of \(10^{26}\) yr, corresponding to a Majorana neutrino mass of 50-100 meV. One of the main goals and challenges of the SuperNEMO detector development programme has been to reach a calorimeter energy resolution, \(\Delta\)E/E, around 3%/\(sqrt(E)\)(MeV) \(\sigma\), or 7%/\(sqrt(E)\)(MeV) FWHM (full width at half maximum), using a calorimeter composed of large volume plastic scintillator blocks coupled to photomultiplier tubes. We describe the R\&D programme and the final design of the SuperNEMO calorimeter that has met this challenging goal.
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