NEMO-3 Detector Research Articles

Search for periodic modulations of the rate of double- β decay of Mo100 in the NEMO-3 detector

Search for periodic modulations of the rate of double- <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>β</mml:mi></mml:math> decay of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mmultiscripts><mml:mi>Mo</mml:mi><mml:mprescripts/><mml:none/><mml:mn>100</mml:mn></mml:mmultiscripts></mml:math> in the NEMO-3 detector

Search for the double-beta decay of 82Se to the excited states of 82Kr with NEMO-3

The double-beta decay of 82Se to the 01+ 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 γ-rays has been performed to search for events in the 2e2γ channel. No evidence of a 2νββ decay to the 01+ state has been observed and a limit of T1/22ν(Se82,0gs+→01+)>1.3×1021y at 90% CL has been set. Concerning the 0νββ decay to the 01+ state, a limit for this decay has been obtained with T1/20ν(Se82,0gs+→01+)>2.3×1022y at 90% CL, independently from the 2νββ decay process. These results are obtained for the first time with a tracko-calo detector, reconstructing every particle in the final state.

Measurement of the double-β decay half-life and search for the neutrinoless double-β decay of 48Ca with the NEMO-3 detector

Neutrinoless double-β decay is a powerful probe of lepton number violating processes that may arise from Majorana terms in neutrino masses, or from supersymmetric, left-right symmetric, and other extensions of the Standard Model. Of the candidate isotopes for the observation of this process, 48Ca has the highest Qββ-value, resulting in decays with energies significantly above most naturally occurring backgrounds. The nucleus also lends itself to precise matrix element calculations within the nuclear shell model. We present the world’s best measurement of the two-neutrino double-β decay of 48Ca, obtained by the NEMO-3 collaboration using 5.25 yr of data recorded with a 6.99 g sample of isotope, yielding ≈ 150 events with a signal to background ratio larger than 3. Neutrinoless modes of double-β decay are also investigated, with no evidence of new physics. Furthermore, these results indicate that two-neutrino double-β decay would be the main source of background for similar future searches using 48Ca with significantly larger exposures.

Search for Neutrinoless Quadruple-β Decay of ^{150}Nd with the NEMO-3 Detector.

We report the results of a first experimental search for lepton number violation by four units in the neutrinoless quadruple-β decay of ^{150}Nd using a total exposure of 0.19kg yr recorded with the NEMO-3 detector at the Modane Underground Laboratory. We find no evidence of this decay and set lower limits on the half-life in the range T_{1/2}>(1.1-3.2)×10^{21} yr at the 90%C.L., depending on the model used for the kinematic distributions of the emitted electrons.

Measurement of the2νββdecay half-life ofNd150and a search for0νββdecay processes with the full exposure from the NEMO-3 detector

We present results from a search for neutrinoless double-$\beta$ ($0\nu\beta\beta$) decay using 36.6 g of the isotope $^{150}$Nd with data corresponding to a live time of 5.25 y recorded with the NEMO-3 detector. We construct a complete background model for this isotope, including a measurement of the two-neutrino double-$\beta$ decay half-life of $T^{2\nu}_{1/2}=$[9.34 $\pm$ 0.22 (stat.) $^{+0.62}_{-0.60}$ (syst.)]$\times 10^{18}$ y for the ground state transition, which represents the most precise result to date for this isotope. We perform a multivariate analysis to search for \zeronu decays in order to improve the sensitivity and, in the case of observation, disentangle the possible underlying decay mechanisms. As no evidence for \zeronu decay is observed, we derive lower limits on half-lives for several mechanisms involving physics beyond the Standard Model. The observed lower limit, assuming light Majorana neutrino exchange mediates the decay, is $T^{0\nu}_{1/2} >$ 2.0 $\times 10^{22}$ y at the 90% C.L., corresponding to an upper limit on the effective neutrino mass of $\langle m_{\nu} \rangle$ $<$ 1.6 - 5.3 eV..

Background constrains of the SuperNEMO experiment for neutrinoless double beta-decay searches

The SuperNEMO experiment is a new generation of experiments dedicated to the search for neutrinoless double beta-decay, which if observed, would confirm the existence of physics beyond the Standard Model. It is based on the tracking and calorimetry techniques, which allow the reconstruction of the final state topology, including timing and kinematics of the double beta-decay transition events, offering a powerful tool for background rejection. While the basic detection strategy of the SuperNEMO detector remains the same as of the NEMO-3 detector, a number of improvements were accomplished for each of detector main components. Upgrades of the detector technologies and development of low-level counting techniques ensure radiopurity control of construction parts of the SuperNEMO detector. A reference material made of glass pellets has been developed to assure quality management and quality control of radiopurity measurements. The first module of the SuperNEMO detector (Demonstrator) is currently under construction in the Modane underground laboratory. No background event is expected in the neutrinoless double beta-decay region in 2.5 years of its operation using 7kg of 82Se. The half-life sensitivity of the Demonstrator is expected to be >6.5·1024 y, corresponding to an effective Majorana neutrino mass sensitivity of |0.2−0.4|eV (90% C.L.). The full SuperNEMO experiment comprising of 20 modules with 100kg of 82Se source should reach an effective Majorana neutrino mass sensitivity of |0.04−0.1| eV, and a half-life limit 1·1026 y.

Results of the search for neutrinoless double-βdecay inMo100with the NEMO-3 experiment

The NEMO-3 detector, which had been operating in the Modane Underground Laboratory from 2003 to 2010, was designed to search for neutrinoless double $\beta$ ($0\nu\beta\beta$) decay. We report final results of a search for $0\nu\beta\beta$ decays with $6.914$ kg of $^{100}$Mo using the entire NEMO-3 data set with a detector live time of $4.96$ yr, which corresponds to an exposure of 34.3 kg$\cdot$yr. We perform a detailed study of the expected background in the $0\nu\beta\beta$ signal region and find no evidence of $0\nu\beta\beta$ decays in the data. The level of observed background in the $0\nu\beta\beta$ signal region $[2.8-3.2]$ MeV is $0.44 \pm 0.13$ counts/yr/kg, and no events are observed in the interval $[3.2-10]$ MeV. We therefore derive a lower limit on the half-life of $0\nu\beta\beta$ decays in $^{100}$Mo of $T_{1/2}(0\nu\beta\beta)> 1.1 \times 10^{24}$ yr at the $90\%$ Confidence Level, under the hypothesis of light Majorana neutrino exchange. Depending on the model used for calculating nuclear matrix elements, the limit for the effective Majorana neutrino mass lies in the range $\langle m_{\nu} \rangle < 0.33$--$0.62$ eV. We also report constraints on other lepton-number violating mechanisms for $0\nu\beta\beta$ decays.

Search for neutrinoless double-beta decay ofMo100with the NEMO-3 detector

We report the results of a search for the neutrinoless double-$\beta$ decay (0$\nu\beta\beta$) of $^{100}$Mo, using the NEMO-3 detector to reconstruct the full topology of the final state events. With an exposure of 34.7 kg.y, no evidence for the 0$\nu\beta\beta$ signal has been found, yielding a limit for the light Majorana neutrino mass mechanism of $T_{1/2}(0\nu\beta\beta)>1.1 \times 10^{24}$ years (90% C.L.) once both statistical and systematic uncertainties are taken into account. Depending on the Nuclear Matrix Elements this corresponds to an upper limit on the Majorana effective neutrino mass of $< m_{\nu} > < 0.3-0.9$ eV (90% C.L.). Constraints on other lepton number violating mechanisms of 0$\nu\beta\beta$ decays are also given. Searching for high-energy double electron events in all suitable sources of the detector, no event in the energy region [3.2-10] MeV is observed for an exposure of 47 kg.y.

Investigation of double beta decay of 100Mo to excited states of 100Ru

Double beta decay of $^{100}$Mo to the excited states of daughter nuclei has been studied using a 600 cm$^3$ low-background HPGe detector and an external source consisting of 2588 g of 97.5% enriched metallic $^{100}$Mo, which was formerly inside the NEMO-3 detector and used for the NEMO-3 measurements of $^{100}$Mo. The half-life for the two-neutrino double beta decay of $^{100}$Mo to the excited 0$^+_1$ state in $^{100}$Ru is measured to be $T_{1/2}=[7.5 \pm{0.6}(stat) \pm {0.6}(syst)]\cdot 10^{20}$ yr. For other $(0\nu + 2\nu)$ transitions to the 2$^+_1$, 2$^+_2$, 0$^+_2$, 2$^+_3$ and 0$^+_3$ levels in $^{100}$Ru, limits are obtained at the level of $\sim (0.25-1.1)\cdot 10^{22}$ yr.

Measurement of theββDecay Half-Life ofTe130with the NEMO-3 Detector

We report results from the NEMO-3 experiment based on an exposure of 1275 days with 661 g of Te130 in the form of enriched and natural tellurium foils. The ββ decay rate of Te130 is found to be greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be T1/22ν=[7.0±0.9(stat)±1.1(syst)]×1020 yr. This represents the most precise measurement of this half-life yet published and the first real-time observation of this decay.Received 11 April 2011DOI:https://doi.org/10.1103/PhysRevLett.107.062504© 2011 American Physical Society

Investigation of double-beta decay with the NEMO-3 detector

The double beta decay experiment NEMO~3 has been taking data since February 2003. The aim of this experiment is to search for neutrinoless ($0\nu\beta\beta$) decay and investigate two neutrino double beta decay in seven different isotopically enriched samples ($^{100}$Mo, $^{82}$Se, $^{48}$Ca, $^{96}$Zr, $^{116}$Cd, $^{130}$Te and $^{150}$Nd). After analysis of the data corresponding to 3.75 y, no evidence for $0\nu\beta\beta$ decay in the $^{100}$Mo and $^{82}$Se samples was found. The half-life limits at the 90% C.L. are $1.1\cdot 10^{24}$ y and $3.6\cdot 10^{23}$ y, respectively. Additionally for $0\nu\beta\beta$ decay the following limits at the 90% C.L. were obtained, $> 1.3 \cdot 10^{22}$ y for $^{48}$Ca, $> 9.2 \cdot 10^{21}$ y for $^{96}$Zr and $> 1.8 \cdot 10^{22}$ y for $^{150}$Nd. The $2\nu\beta\beta$ decay half-life values were precisely measured for all investigated isotopes.

Measurement of the two neutrino double beta decay half-life of Zr-96 with the NEMO-3 detector

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.

The NEMO-3 experiment and the SuperNEMO project

The NEMO experiment investigates the neutrinoless double beta decay. The NEMO-3 detector is collecting data in the Frejus Underground Laboratory. The goal of the SuperNEMO detector is to reach a sensitivity of the order of 10 26 year on the half-life of the β β 0 ν process. The chosen isotopes for the future detector are 82Se and 150Nd, because of the reduced background. The collaboration has started a 3-year R& D development on all components: tracking detector, calorimeter, source enrichment and purification and radiopurity measurements.

Simulation of double beta decay in the ‘‘SeXe’’ TPC

In 2004, the NEMO collaboration has started some preliminary studies for a next-generation double beta decay experiment: SuperNEMO. The possibility to use a large gaseous TPC has been investigated using simulation and extrapolation of former experiments. In this talk, I report on the reasons why such techniques have not been selected in 2004 and led the NEMO collaboration to reuse the techniques implemented within the NEMO3 detector.

Double-beta-decay experiment NEMO-3: Preliminary results of phase I (2003–2004)

The NEMO-3 detector has been taking data in the Frejus underground laboratory (LSM, France) since February 2003 and is devoted to the search for neutrinoless double-beta decay (0νββ). 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 ∼7 kg of 100Mo and ∼1 kg of 82Se. The corresponding limits for the half-lives are T 1/2(0νββ) > 4.6 × 1023 yr for 100Mo and T 1/2(0νββ) > 1.0 × 1023 yr for 82Se (90% C.L.). They lead to the following limits for the effective Majorana neutrino mass: 〈m ν〉 < 0.7–2.8 eV for 100Mo and 〈m ν〉 < 1.8–4.9 eV for 82Se. The half-lives of the two-neutrino double-beta decay (2νββ) have been measured for 100Mo, 82Se, 116Cd, 150Nd, and 96Zr and reported here as well.

The SuperNEMO project

Neutrinoless double-beta decay (ββ(0ν)) is the most sensitive process in the search for leptonic number violation and its discovery would prove that the neutrino is a Majorana particle. From the experience of the NEMO-3 detector construction and data analysis, the NEMO Collaboration proposes a three-year R&D program in order to design a detector (SuperNEMO) sensitive to a ββ(0ν) period of few 1026 yr coupling track reconstruction and calorimeter.

Search for neutrinoless double beta decay with the NEMO-3 detector: first results

The NEMO-3 detector, which has been operating in the Frejus Underground Laboratory since February 2003, is devoted to searching for neutrinoless double beta decay ( β β 0 ν ) . The expected performance of the detector has been successfully achieved. Half-lives of the two neutrinos double beta decay ( β β 2 ν ) have been measured for 100Mo, 82Se, 96Zr, 116Cd and 150Nd. After 265 days of data collection from February 2003 until March 2004, no evidence for neutrinoless double beta decay ( β β 0 ν ) was found from ∼ 7 kg of 100Mo and ∼ 1 kg of 82Se. The corresponding lower limits for the half-lives are 3.5 × 10 23 years at 90% C.L for 100Mo and 1.9 × 10 23 years for 82Se. Limits for the effective Majorana neutrino mass are m ν > 0.7 − 1.2 eV for 100Mo and m ν > 1.3 − 3.2 eV for 82Se. Radon is the dominant background today and a Radon-free purification system will be in operation by the end of September 2004. The NEMO-3 expected sensitivity after 5 years of data is 0.2 eV.

Investigation of double-beta-decay processes at the NEMO-3 tracking detector

In order to investigate double-beta-decay processes with a sensitivity of up to about 1025 yr, the NEMO Collaboration created the NEMO-3 tracking detector consisting of Geiger counters for reconstructing tracks and plastic scintillators for measuring energy. A brief description of the NEMO-3 detector is given, and its main features are presented. The first preliminary results for 100Mo, 82Se, 116Cd, and 150Nd are quoted.

Search for neutrinoless double beta decay with the NEMO-3 detector: first results

The NEMO-3 detector, which has been operating in the Frejus Underground Laboratory since February 2003, is devoted to searching for neutrinoless double beta decay (\beta\beta 0 \nu). The expected performance of the detector has been successfully achieved. Half-lives of the two neutrinos double beta decay (\beta\beta 2 \nu$) have been measured for ^{100} Mo, ^{82}Se, ^{96}Zr, ^{116}Cd and ^{150}Nd. After 265 days of data collection from February 2003 until March 2004, no evidence for neutrinoless double beta decay (\beta\beta 0 \nu) was found from \sim 7 kg of ^{100} Mo and \sim 1 kg of ^{82} Se. The corresponding lower limits for the half-lives are 3.5 \times 10^{23} years at 90% C.L for ^{100} Mo and 1.9 \times 10^{23} years for ^{82}Se. Limits for the effective Majorana neutrino mass are < \hspace{-0.5mm} m_{\nu} \hspace{-0.5mm} > < 0.7-1.2 eV for ^{100} Mo and \linebreak < \hspace{-0.5mm} m_{\nu \hspace{-0.5mm} > < 1.3-3.2 eV for ^{82}Se. Radon is the dominant background today and a Radon-free purification system will be in operation by the end of september 2004. The NEMO-3 expected sensitivity after 5 years of data is 0.2 eV.

Nemo-3 double beta decay experiment: Present status

The objective of the NEMO Collaboration is to search for neutrinoless double beta decay with sensitivity for the effective neutrino mass on the order of (0.1-0.3) eV. The NEMO-3 detector has been operating in the Fréjus Underground Laboratory since June of 2002. In this report, the design of the detector is reviewed and some characteristics are presented. Finally, the first preliminary results for double beta decay of 100Mo, 82Se, 116Cd and 150Nd are reported.