11 pages included 8 figures and 3 tables, Invited talk at the CISPN ("Columbia Int. Symp. on Neutrino Physics"; Columbia, USA, May 15-17, 2008) and at the 2nd Int. Conf. NPAE-2008 (Kyiv, Ukraine, June 9-15, 2008)
The double beta decay experiment NEMO~3 has been taking data since February 2003. The aim of this experiment is to search for neutrinoless decay and investigate two neutrino double beta decay in seven different enriched isotopes ($^{100}$Mo,$^{82}$Se, $^{48}$Ca, $^{96}$Zr, $^{116}$Cd, $^{130}$Te and $^{150}$Nd). After analysis of the data corresponding to 693 days, no evidence for $0νββ$ decay in $^{100}$Mo and $^{82}$Se was found. The half-life limits at 90% C.L. are $5.8\cdot 10^{23}$ y and $2.1\cdot 10^{23}$ y, respectively. Using $\sim$ 940 days of data, preliminary results were obtained for $^{48}$Ca, $^{96}$Zr and $^{150}$Nd. For two neutrino decay half-life values were measured, $T_{1/2}(^{48}{\rm Ca}) = [4.4^{+0.5}_{-0.4}(stat) \pm 0.4(syst)] \cdot 10^{19}$ y, $T_{1/2}(^{96}{\rm Zr}) = [2.3 \pm 0.2(stat) \pm 0.3(syst)] \cdot 10^{19}$ y and $T_{1/2}(^{150}{\rm Nd}) = [9.2^{+0.25}_{-0.22}(stat) \pm 0.62(syst)] \cdot 10^{18}$ y. Also for $0νββ$ decay the following limits at 90% C.L. were obtained, $> 1.3 \cdot 10^{22}$ y for $^{48}$Ca, $> 8.6 \cdot 10^{21}$ y for $^{96}$Zr and > 1.8 \cdot 10^{22}$ y for $^{150}$Nd.
The NEMO-3 detector installed in the Modane Underground Laboratory (LSM, France) is running to search for neutrinoless double beta decay ($β\beta0ν$) with an expected sensitivity for the effective Majorana neutrino mass down to 0.1 eV. New preliminary limits (90% CL), $T_{1/2}(β\beta0ν) > 1.0 \cdot 10^{23}$ y (massive mechanism) and $T_{1/2}(β\beta0ν) > 1.9 \cdot 10^{23}$ y (right-handed currents) were established analyzing $^{100}$Mo data collected during 3800h of measurements in 2003. This is the world's best result for $^{100}$Mo. New preliminary half-lives of $β\beta2ν$-mode for $^{100}$Mo…
The double beta decay experiment NEMO~3 has been taking data since February 2003. The aim of this experiment is to search for neutrinoless ($0νββ$) 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 $0νββ$ 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 $0νββ$ decay …
NEMO 3 is a currently running experiment to search for the neutrinoless double beta decay and to study the two-neutrino double beta decay with 10kg of enriched isotopes. On the basis of the first two years of data taking, a limit on the neutrinoless decay $T_{1/2}^{0ν} > 5.8\cdot10^{23}$ y at 90% CL was obtained with $^{100}Mo$. The two-neutrino double beta decay half-lives were measured for all seven $ββ$ isotopes located in NEMO 3. New results are obtained for two of these isotopes: $^{48}Ca T_{1/2}^{2ν}=[4.4 ^{+0.5}_{-0.4} (stat) \pm 0.4 (syst)]\cdot10^{19}$ y, $^{96}Zr T_{1/2}^{2ν}=[2.3 \p…
In the double beta decay experiment NEMO~3 a precise knowledge of the background in the signal region is of outstanding importance. This article presents the methods used in NEMO~3 to evaluate the backgrounds resulting from most if not all possible origins. It also illustrates the power of the combined tracking-calorimetry technique used in the experiment.
The half-life for double beta decay of 150-Nd has been measured by the NEMO-3 experiment at the Modane Underground Laboratory. Using 924.7 days of data recorded with 36.55 g of 150-Nd the half-life for 2nubb decay is measured to be T_1/2^2nu = (9.11+0.25_-0.22}(stat.) +- 0.63 (syst.)) x 10^18 years. The observed limit on the half-life for neutrinoless double beta decay is found to be T_1/2^{0nu} > 1.8 x 10^22 years at 90 % Confidence Level. This translates into a limit on the effective Majorana neutrino mass of <m_{neutrino}><4.0-6.3 eV if the nuclear deformation is taken into account. We also…
NEMO 3 is a double beta decay experiment. A part of low background data was analysed, preliminary result on bb2nu decay of 130Te obtained: T_{1/2} = 7.6 \+- 1.5(stat) +- 0.8(syst) * 10^{20} y$. No bb0nu signal was observed: T_{1/2}^{0ν}(100Mo) > 5.8 *10^{23} y and T_{1/2}^{0ν}(82Se) > 2.1 * 10^{23} y (90% C.L.). SuperNEMO project R&D has started.
Using 9.4 g of Zr-96 and 1221 days of data from the NEMO-3 detector corresponding to 0.031 kg yr, the obtained 2vbb decay half-life measurement is [2.35 +/- 0.14(stat) +/- 0.16(syst)] x 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 2v nuclear matrix element is extracted using the measured 2vbb half-life and is 0.049 +/- 0.002. Constraints on 0vbb decay have also been set.
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 tr…
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 $(0ν+ 2ν)$ transitions to the 2$^+_1$, 2$^+_2$, 0$^+_2$, 2$^+_3$ and 0$^+_3$ le…
This Letter reports results from the NEMO-3 experiment based on an exposure of 1275 days with 661g of 130Te in the form of enriched and natural tellurium foils. The double beta decay rate of 130Te is found to be greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be T1/2 = (7.0 +/- 0.9(stat) +/- 1.1(syst)) x 10^{20} yr. This represents the most precise measurement of this half-life yet published and the first real-time observation of this decay.
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 …
SuperNEMO is a next-generation double beta decay experiment based on the successful tracking plus calorimetry design approach of the recently stopped NEMO3 experiment. SuperNEMO can study a range of isotopes, but the baseline isotope is $^{82}$Se. The total isotope mass will be 100--200 kg. A sensitivity to a $0νββ$ half-life greater than $10^{26}$ years can be reached which gives access to Majorana neutrino masses of 50--100 meV. Having successfully completed R&D stage the SuperNEMO Collaboration has commenced the construction of the first module, the Demonstrator. The present status of Super…
We report the results of a search for the neutrinoless double-$β$ decay (0$νββ$) 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$νββ$ signal has been found, yielding a limit for the light Majorana neutrino mass mechanism of $T_{1/2}(0νββ)>1.1 \times 10^{24}$ 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 $< m_ν > < 0.3-0.9$ eV (…
Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay ($2νββ$) half-life of $^{82}$Se as $T_{1/2}^{2ν} = \left[ 9.39 \pm 0.17\,\left(\mbox{stat}\right) \pm 0.58\,\left(\mbox{syst}\right)\right] \times 10^{19}$ y under the single-state dominance hypothesis for this nuclear transition. The corresponding nuclear matrix element is $\left|M^{2ν}\right| = 0.0498 \pm 0.0016$. In addition, a search for neutrinoless double beta decay ($0νββ$) 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…
The NEMO-3 experiment at the Modane Underground Laboratory has investigated the double-$β$ decay of $^{48}{\rm Ca}$. Using $5.25$ yr of data recorded with a $6.99\,{\rm g}$ sample of $^{48}{\rm Ca}$, approximately $150$ double-$β$ decay candidate events have been selected with a signal-to-background ratio greater than $3$. The half-life for the two-neutrino double-$β$ decay of $^{48}{\rm Ca}$ has been measured to be $T^{2ν}_{1/2}\,=\,[6.4\, ^{+0.7}_{-0.6}{\rm (stat.)} \, ^{+1.2}_{-0.9}{\rm (syst.)}] \times 10^{19}\,{\rm yr}$. A search for neutrinoless double-$β$ decay of $^{48}{\rm Ca}$ yields…
The background induced by radioactive impurities of $^{208}\rm Tl$ and $^{214}\rm Bi$ 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.
In the field of Double Beta Decay (DBD) searches, the use of high resolution detectors in which background can be actively discriminated is very appealing. Scintillating bolometers containing a Double Beta Decay emitter can largely fulfill this very interesting possibility. In this paper we present the latest results obtained with CdWO4 and CaMoO4 crystals. Moreover we report, for the first time, a very interesting feature of CaMoO4 bolometers: the possibility to discriminate beta-gamma events from those induced by alpha particles thanks to different thermal pulse shape.
NEXT-DEMO is a 1:4.5 scale prototype of the NEXT100 detector, a high-pressure xenon gas TPC that will search for the neutrinoless double beta decay of $^{136}$Xe. X-ray energy depositions produced by the de-excitation of Xenon atoms after the interaction of gamma rays from radioactive sources have been used to characterize the response of the detector obtaining the spatial calibration needed for close-to-optimal energy resolution. Our result, 5.5% FWHM at 30 keV, extrapolates to 0.6% FWHM at the Q value of $^{136}$Xe. Additionally, alpha decays from radon have been used to measure several dete…
In this report I will briefly review the motivation and history of double beta decay search since the first consideration of two neutrino process (2$β(2ν)$) by Maria Goeppert-Mayer in 1935. The first experiments on search for double beta decay in the late of 1940's and beginning of 1950's are considered. It is underlined that for the first time the 2$β(2ν)$ decay has been registered in geochemical experiment with $^{130}$Te in 1950. In direct (counter) experiment this type of decay for the first time has been registered in $^{82}$Se by Michael Moe's group in 1987. Now two neutrino double beta …
All existing positive results on two neutrino double beta decay in different nuclei were analyzed. Using the procedure recommended by the Particle Data Group, weighted average values for half-lives of $^{48}$Ca, $^{76}$Ge, $^{82}$Se, $^{96}$Zr, $^{100}$Mo, $^{100}$Mo - $^{100}$Ru ($0^+_1$), $^{116}$Cd, $^{130}$Te, $^{136}$Xe, $^{150}$Nd, $^{150}$Nd - $^{150}$Sm ($0^+_1$) and $^{238}$U were obtained. Existing geochemical data were analyzed and recommended values for half-lives of $^{128}$Te, and $^{130}$Ba are proposed. Given the measured half-life values, nuclear matrix elements were calculate…
Cryogenic bolometers, with their excellent energy resolution, flexibility in material, and availability in high purity, are excellent detectors for the search for neutrinoless double beta decay. Kilogram-size single crystals of TeO_2 are utilized in CUORICINO for an array with a total detector mass of 40.7 kg. CUORICINO currently sets the most stringent limit on the halflife of Te-130 of T > 2.4x10^{24} yr (90% C.L.), corresponding to a limit on the effective Majorana neutrino mass in the range of < 0.2-0.9 eV. Based on technology developed for CUORICINO and its predecessors, CUORE is a next-g…
In the field of Double Beta Decay (DBD) searches the possibility to have high resolution detectors in which background can be discriminated is very appealing. This very interesting possibility can be largely fulfilled in the case of a scintillating bolometer containing a Double Beta Decay emitter whose transition energy exceeds the one of the natural gamma line of 208Tl. We present the latest results obtained in the development of such a kind of scintillating bolometer. For the first time an array of five CdWO4 (116Cd has a Double Beta Decay transition energy of 2805 keV) crystals is tested. T…
Even after the discovery of neutrino flavour oscillations, based on data from atmospheric, solar, reactor, and accelerator experiments, many characteristics of the neutrino remain unknown. Only the neutrino square-mass differences and the mixing angle values have been estimated, while the value of each mass eigenstate still hasn't. Its nature (massive Majorana or Dirac particle) is still escaping. Neutrinoless double beta decay ($0ν$-DBD) experimental discovery could be the ultimate answer to some delicate questions of elementary particle and nuclear physics. The Majorana description of neutri…
The GEM project is designed for the next generation 2 beta decay experiments with 76-Ge. One ton of ''naked'' HP Ge detectors (natural at the first GEM-I phase and enriched in 76-Ge to 86% at the second GEM-II stage) are operating in super-high purity liquid nitrogen contained in the Cu vacuum cryostat (sphere with diameter 5 m). The latest is placed in the water shield. Monte Carlo simulation evidently shows that sensitivity of the experiment (in terms of the T1/2 limit for neutrinoless 2 beta decay) is 10^27 yr with natural HP Ge crystals and 10^28 yr with enriched ones. These bounds corresp…
Neutrinoless double beta decay is the only process known so far able to test the neutrino intrinsic nature: its experimental observation would imply that the lepton number is violated by two units and prove that neutrinos have a Majorana mass components, being their own anti-particle. While several experiments searching for such a rare decay have been performed in the past, a new generation of experiments using different isotopes and techniques have recently released their results or are taking data and will provide new limits, should no signal be observed, in the next few years to come. The p…
The CUORE experiment is a large bolometric array searching for the lepton number violating neutrino-less double beta decay ($0νββ$) in the isotope $\mathrm{^{130}Te}$. In this work we present the latest results on two searches for the double beta decay (DBD) of $\mathrm{^{130}Te}$ to the first $0^{+}_2$ excited state of $\mathrm{^{130}Xe}$: the $0νββ$ decay and the Standard Model-allowed two-neutrinos double beta decay ($2νββ$). Both searches are based on a 372.5 kg$\times$yr TeO$_2$ exposure. The de-excitation gamma rays emitted by the excited Xe nucleus in the final state yield a unique sign…
In the current 3nu paradigm, flavor oscillations probe 3 mixing angles (theta_12, theta_23, theta_13), one CP phase delta, and two squared mass differences delta m^2>0 and Delta m^2, where sign(Delta m^2)=+ (-) for normal (inverted) ordering. Absolute nu masses can be probed by the effective m_beta in beta decay, by the total mass Sigma in cosmology and, if neutrinos are Majorana, by another effective m_{beta beta} in 0nu2beta decay. Within an updated global analysis of (non)oscillation data, we constrain these 3nu parameters, both separately and in selected pairs, and highlight the concordanc…
Within the standard three-neutrino framework, the absolute neutrino masses and their ordering (either normal, NO, or inverted, IO) are currently unknown. However, the combination of current data coming from oscillation experiments, neutrinoless double beta decay searches, and cosmological surveys, can provide interesting constraints for such unknowns in the sub-eV mass range, down to O(0.1) eV in some cases. We discuss current limits on absolute neutrino mass observables by performing a global data analysis, that includes the latest results from oscillation experiments, neutrinoless double bet…
We use results from long-time core-collapse supernovae simulations to investigate the impact of the late time evolution of the ejecta and of the nuclear physics input on the calculated r-process abundances. Based on the latest hydrodynamical simulations, heavy r-process elements cannot be synthesized in the neutrino-driven winds that follow the supernova explosion. However, by artificially increasing the wind entropy, elements up to A=195 can be made. In this way one can reproduce the typical behavior of high-entropy ejecta where the r-process is expected to occur. We identify which nuclear ph…
The Neutrino Experiment with a Xenon TPC (NEXT), intended to investigate the neutrinoless double beta decay using a high-pressure xenon gas TPC filled with Xe enriched in 136Xe at the Canfranc Underground Laboratory in Spain, requires ultra-low background conditions demanding an exhaustive control of material radiopurity and environmental radon levels. An extensive material screening process is underway for several years based mainly on gamma-ray spectroscopy using ultra-low background germanium detectors in Canfranc but also on mass spectrometry techniques like GDMS and ICPMS. Components from…
The sensitivity of neutrinoless double beta (0n2b) decay experiments is mainly depended on the internal background of a detector which, in its turn, is defined by the purity of material and possibility for selection of background events. The AMoRE (Advanced Mo based Rare process Experiment) collaboration plans to use 40Ca100MoO4 scintillation crystals as a detector for search of 0n2b decay of 100Mo isotope. A purpose of this paper is further investigation of internal background of 40Ca100MoO4 scintillation elements with a low background setup at YangYang underground laboratory. We present new …
The MAJORANA DEMONSTRATOR is an experiment constructed to search for neutrinoless double-beta decay in $^{76}$Ge and to demonstrate the feasibility to deploy a large-scale experiment in a phased and modular fashion. It consists of two modules of natural and $^{76}$Ge-enriched germanium detectors totalling 44.1 kg, operating at the 4850' level of the Sanford Underground Research Facility in Lead, South Dakota, USA. Commissioning of the experiment began in June 2015, followed by data production with the full detector array in August 2016. The ultra-low background and record energy resolution ach…
