Half-life Of Double Beta Decay Research Articles

Recent results on heavy-ion induced reactions of interest for neutrinoless double beta decay at INFN-LNS

The possibility to use a special class of heavy-ion induced direct reactions, such as double charge exchange reactions, is discussed in view of their application to extract information that may be helpful to determinate the nuclear matrix elements entering in the expression of neutrinoless double beta decay half-life. The methodology of the experimental campaign presently running at INFN - Laboratori Nazionali del Sud is reported andthe experimental challenges characterizing such activity are described.

Double-beta decay and its potential to explore beyond standard model physics

Double-beta decay (DBD) is a rare nuclear process of great interest due to its potential to provide information about physics beyond the Standard Model (BSM). For example, the discovery of the neutrinoless double-beta [Formula: see text] decay mode could give information about important issues such as possible violations of Lorentz symmetry and lepton number, nature of neutrinos (are they Dirac- or Majorana-like particles?), neutrino absolute masses, neutrino mass hierarchy, existence of heavy (sterile) neutrinos, etc. In the theoretical study of DBD, one needs a precise calculation of the nuclear matrix elements (NMEs) and phase space factors (PSFs) entering the half-lives formulas, for different decay modes, transitions and mechanisms of occurrence. Reliable computations of these quantities may result in reliable predictions of DBD half-lives and constrains of the BSM parameters related to the possible mechanisms that can contribute to the [Formula: see text] decay. In this paper, I briefly review the theoretical challenges in the study of [Formula: see text] decay. I describe the computation of the NMEs and PSFs and present results for a number of selected nuclei. Then, I show the broader potential of this process to provide information about BSM physics and present new upper limits for parameters associated with light neutrino, heavy neutrino and SUSY exchange mechanisms. Finally, I suggest a more consistent approach to calculate the NMEs and PSFs, namely to compute directly their product and discuss some possibilities to reduce the errors related to the uncertain value of the axial-vector constant.

Short-range neutrinoless double beta decay mechanisms

Neutrinoless double beta decay can significantly help to shed light on the issue of non-zero neutrino mass, as observation of this lepton number violating process would imply neutrinos are Majorana particles. However, the underlying interaction does not have to be as simple as the standard neutrino mass mechanism. The entire variety of neutrinoless double beta decay mechanisms can be approached effectively. In this work we focus on a theoretical description of short-range effective contributions to neutrinoless double beta decay, which are equivalent to 9-dimensional effective operators incorporating the appropriate field content. We give a detailed derivation of the nuclear matrix elements and phase space factors corresponding to individual terms of the effective Lagrangian. Using these, we provide general formulae for the neutrinoless double beta decay half-life and angular correlation of the outgoing electrons.

Final results on {}^mathbf{82 }{hbox {Se}} double beta decay to the ground state of {}^mathbf{82 }{hbox {Kr}} from the NEMO-3 experiment

Using data from the NEMO-3 experiment, we have measured the two-neutrino double beta decay (2nu beta beta ) half-life of ^{82}Se as T_{smash {1/2}}^{2nu } !=! left[ 9.39 pm 0.17left( text{ stat }right) pm 0.58left( text{ 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^{2nu }right| = 0.0498 pm 0.0016. In addition, a search for neutrinoless double beta decay (0nu 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}^{0nu } > 2.5 times 10^{23} ,text{ y } ,(90%,text{ 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{-}3.0right) ,text{ eV }, where the range reflects 0nu beta beta nuclear matrix element values from different calculations. Furthermore, constraints on lepton number violating parameters for other 0nu beta beta mechanisms, such as right-handed currents, majoron emission and R-parity violating supersymmetry modes have been set.

Interpolating formula for the 0νββ -decay half-life in the case of light and heavy neutrino mass mechanisms

We revisit the "interpolating formula" proposed in our previous publication. It allows one to calculate the neutrinoless double beta decay ($0\nu\beta\beta$-decay) half-life for arbitrary neutrino mass without involvement of the complicated results for nuclear matrix elements (NME) obtained within specific nuclear structure models. The formula derives from the finding that the value of a properly normalized ratio of the NMEs for the light and heavy neutrino mass mechanisms weakly depends on isotope. From this fact it follows, in particular, that the light and heavy neutrino mass mechanisms can hardly be distinguished in a model independent way searching for $0\nu\beta\beta$-decay of different nuclei. Here we show that this formula holds for all the known nuclear structure approaches. We give a mathematical justification of our results examining analytical properties of the NMEs. We also consider several simplified benchmark scenarios within left-right symmetric models and analyze the conditions for the dominance of the light or heavy neutrino mass mechanisms in $0\nu\beta\beta$-decay.

The CUORE and CUORE-0 experiments at LNGS

The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for neutrinoless double beta decay that has been able to reach the 1-ton scale. The detector consists of an array of 988 TeO2 crystals arranged in a cylindrical compact structure of 19 towers. The construction of the experiment and, in particular, the installation of all towers in the cryostat was completed in August 2016 and commissioning started in fall 2016. The experiment has completed the pre-operation phase and is currently in data taking. We present here the achievements of CUORE during the commissioning phase and the limit on the 130Te half-life for the neutrinoless double beta decay that has been released after the first 3 weeks of collected data. Physics results from CUORE-0 will also be updated.

Silicon Carbide detectors for nuclear physics experiments at high beam luminosity

Silicon carbide is a very promising material for next generation nuclear physics experiments at high beam luminosity. Such activities require devices able to sustain high fluxes of particles (up to 1014 ions/cm2) in order to determine the cross sections of very rare nuclear phenomena. One of these activities is the NUMEN project, which aims, through the double charge exchange reactions, to impact in the determination of nuclear matrix elements entering in the expression of half-life of the neutrino-less double beta decay. Due to the very low cross sections, these features can just be explored at fluences which exceed by far those tolerated in state of the art solid state detectors, typically used in this kind of experiments. The SiC technology offers today an ideal response to such challenges, giving the opportunity to cope the excellent properties of silicon detectors with the radiation hardness, thermal stability and visible blindness of SiC material.

Experimental challenges for the measurement of the 116Cd(20Ne,20O)116Sn double charge exchange reaction at 15 AMeV

The knowledge of the nuclear matrix elements (NME) entering in the expression of the half-life of the neutrinoless double beta decay is fundamental for neutrino physics. Information on the nuclear matrix elements can be obtained by measuring the absolute cross section of double charge exchange nuclear reactions. The two processes present some similarities, the initial and final-state wave functions are the same and the transition operators are similar. The experimental measurements of double charge exchange reactions induced by heavy ions present a number of challenging aspects, since such reactions are characterized by very low cross sections. Such difficulties are discussed for the measurement of the 116Cd(20Ne,20O)116Sn reaction at 15 AMeV.

Studies on two neutrino double beta decay

The study aimed to develop an empirical formula for phase space factor and nuclear matrix element to analyse two neutrino double beta decay. The present work also extended to compute phase space factor using Primakoff–Rosen approximation. Using these two formulae for phase space factors we have computed two neutrino double beta decay half lives. Comparisons of the calculated half lives with the corresponding experimental values are also done. The empirical formula predictions are found to be in good agreement with the experimental data. The empirical formula is applied to various isotopes exhibiting single beta decay and our prediction on the possibility of two neutrino double beta decay will be very useful for the future experiments.

Development of ^{100}hbox {Mo}-containing scintillating bolometers for a high-sensitivity neutrinoless double-beta decay search

This paper reports on the development of a technology involving ^{100}hbox {Mo}-enriched scintillating bolometers, compatible with the goals of CUPID, a proposed next-generation bolometric experiment to search for neutrinoless double-beta decay. Large mass (sim 1~hbox {kg}), high optical quality, radiopure ^{100}hbox {Mo}-containing zinc and lithium molybdate crystals have been produced and used to develop high performance single detector modules based on 0.2–0.4 kg scintillating bolometers. In particular, the energy resolution of the lithium molybdate detectors near the Q-value of the double-beta transition of ^{100}hbox {Mo} (3034 keV) is 4–6 keV FWHM. The rejection of the alpha -induced dominant background above 2.6 MeV is better than 8sigma . Less than 10~upmu hbox {Bq/kg} activity of ^{232}hbox {Th}, (^{228}hbox {Th}) and ^{226}hbox {Ra} in the crystals is ensured by boule recrystallization. The potential of ^{100}hbox {Mo}-enriched scintillating bolometers to perform high sensitivity double-beta decay searches has been demonstrated with only 10~hbox {kg}times hbox {d} exposure: the two neutrino double-beta decay half-life of ^{100}hbox {Mo} has been measured with the up-to-date highest accuracy as T_{1/2} = [6.90 ± 0.15(stat.) ± 0.37(syst.)] times ~10^{18}~hbox {years}. Both crystallization and detector technologies favor lithium molybdate, which has been selected for the ongoing construction of the CUPID-0/Mo demonstrator, containing several kg of ^{100}hbox {Mo}.

The SuperNEMO calorimeter

The SuperNEMO double beta decay project is a modular tracker-calorimeter experiment that will reach a sensitivity to the neutrinoless double beta decay half-life of ∼ 1026 years, corresponding to a Majorana neutrino mass of 50-100 meV. The main calorimeter is based on 440 Optical Modules made of large volume plastic scintillators (10L) coupled with large area photomultipliers (Hamamatsu R5912-Mod). They are assembled in walls surrounding the isotope foil and the tracking volume. One of the main challenges of the SuperNEMO detector development programme was to reach an energy resolution, better than 8%(FWHM) at 1 MeV. The other challenge was to satisfy the radiopurity requirements for all the calorimeter materials. The calorimeter design of the first SuperNEMO module is presented as well as its performances and the status of its construction under way in the Modane underground laboratory.

Development of an optical simulation for the SuperNEMO calorimeter

The SuperNEMO double beta decay project is a modular tracker-calorimeter based experiment. The aim of this project is to reach a sensitivity of the order of 1026 years concerning the neutrinoless double beta decay half-life, corresponding to a Majorana neutrino mass of 50-100 meV. The main calorimeter of the SuperNEMO demonstrator is based on 520 Optical Modules made of large volume plastic scintillators (10L) coupled with large area photomultipliers (Hamamatsu R5912-MOD and R6594). The design of the calorimeter is optimized for the double beta decay detection and allows gamma tagging for background rejection. In large volumes of scintillators, a similar deposited energy by electrons or photons will give different visible energy and signal shapes due to different interactions inside the scintillator. The aim of the optical simulation, developed for SuperNEMO, is to model the Optical Module response on the energy and time performances, regarding the particle type.

First results on 76Ge neutrinoless double beta decay from CDEX-1 experiment

We report the first results on 76Ge neutrinoless double beta decay from stage one of the China dark-matter experiment (CDEX). A p-type point-contact high-purity germanium detector with a mass of 994 g has been installed to detect neutrinoless double beta decay events, as well as to directly detect dark matter particles. An exposure of 304 kg d has been analyzed over a wide spectral band from 500 keV to 3 MeV. The average event rate obtained was about 0.012 counts per keV per kg per day over the 2.039 MeV energy range. The half-life of 76Ge neutrinoless double beta decay derived based on this result is T 1/2 0ν >6.4×1022 yr (90% C.L.). An upper limit on the effective Majorana-neutrino mass of 5.0 eV has been achieved.

New limit for the half-life of double beta decay of 94Zr to the first excited state of 94Mo

Neutrinoless Double Beta Decay is a phenomenon of fundamental interest in particle physics. The decay rates of double beta decay transitions to the excited states can provide input for Nuclear Transition Matrix Element calculations for the relevant two neutrino double beta decay process. It can be useful as supplementary information for the calculation of Nuclear Transition Matrix Element for the neutrinoless double beta decay process. In the present work, double beta decay of $^{94}$Zr to the $2^{+}_{1}$ excited state of $^{94}$Mo at 871.1 keV is studied using a low background $\sim$ 230 cm$^3$ HPGe detector. No evidence of this decay was found with a 232 g.y exposure of natural Zirconium. The lower half-life limit obtained for the double beta decay of $\rm^{94}Zr$ to the $2^{+}_{1}$ excited state of $\rm^{94}Mo$ is $T_{1/2} (0\nu + 2\nu)> 3.4 \times 10^{19}$ y at 90% C.L., an improvement by a factor of $\sim$ 4 over the existing experimental limit at 90\% C.L. The sensitivity is estimated to be $T_{1/2} (0\nu + 2\nu) > 2.0\times10^{19}$ y at 90% C.L. using the Feldman-Cousins method.

Measurement of the two-neutrino double-beta decay half-life of ^{130}Te with the CUORE-0 experiment

We report on the measurement of the two-neutrino double-beta decay half-life of ^{130}Te with the CUORE-0 detector. From an exposure of 33.4 kg year of TeO_2, the half-life is determined to be T_{1/2}^{2nu } = [8.2 ± 0.2 (stat.) ± 0.6 (syst.)] times 10^{20} year. This result is obtained after a detailed reconstruction of the sources responsible for the CUORE-0 counting rate, with a specific study of those contributing to the ^{130}Te neutrinoless double-beta decay region of interest.

Charged lepton flavour violcxmation and neutrinoless double beta decay in left-right symmetric models with type I+II seesaw

We study the new physics contributions to neutrinoless double beta decay ($0\nu\beta \beta$) half-life and lepton flavour violation (LFV) amplitude within the framework of the minimal left-right symmetric model (MLRSM). Considering all possible new physics contributions to $0\nu\beta \beta$ and charged lepton flavour violation $\mu \rightarrow e \gamma, \mu \rightarrow 3e$ in MLRSM, we constrain the parameter space of the model from the requirement of satisfying existing experimental bounds. Assuming the breaking scale of the left-right symmetry to be $\mathcal{O}(1)$ TeV accessible at ongoing and near future collider experiments, we consider the most general type I+II seesaw mechanism for the origin of tiny neutrino masses. Choosing the relative contribution of the type II seesaw term allows us to calculate the right handed neutrino mass matrix as well as Dirac neutrino mass matrix as a function of the model parameters, required for the calculation of $0\nu\beta \beta$ and LFV amplitudes. We show that such a general type I+II seesaw structure results in more allowed parameter space compared to individual type I or type II seesaw cases considered in earlier works. In particular, we show that the doubly charged scalar masses $M_{\Delta}$ are allowed to be smaller than the heaviest right handed neutrino mass $M_N$ from the present experimental bounds in these scenarios which is in contrast to earlier results with individual type I or type II seesaw showing $M_{\Delta} > M_N$.

The MAGNEX spectrometer: Results and perspectives

This article discusses the main achievements and future perspectives of the MAGNEX spectrometer at the INFN-LNS laboratory in Catania (Italy). MAGNEX is a large acceptance magnetic spectrometer for the detection of the ions emitted in nuclear collisions below Fermi energy. In the first part of the paper an overview of the MAGNEX features is presented. The successful application to the precise reconstruction of the momentum vector, to the identification of the ion masses and to the determination of the transport efficiency is demonstrated by in-beam tests. In the second part, an overview of the most relevant scientific achievements is given. Results from nuclear elastic and inelastic scattering as well as from transfer and charge exchange reactions in a wide range of masses of the colliding systems and incident energies are shown. The role of MAGNEX in solving old and new puzzles in nuclear structure and direct reaction mechanisms is emphasized. One example is the recently observed signature of the long searched Giant Pairing Vibration. Finally, the new challenging opportunities to use MAGNEX for future experiments are briefly reported. In particular, the use of double charge exchange reactions toward the determination of the nuclear matrix elements entering in the expression of the half-life of neutrinoless double beta decay is discussed. The new NUMEN project of INFN, aiming at these investigations, is introduced. The challenges connected to the major technical upgrade required by the project in order to investigate rare processes under high fluxes of detected heavy ions are outlined.

Latest results from KamLAND-Zen second phase

We report on preliminary results from the second phase of KamLAND-Zen double beta decay search experiment based on 114.8 days with 383 kg of 136Xe. Second phase of KamLAND-Zen was started after the purification to reduce the dominant 110mAg background identified by first phase data. The background was reduced by more than a factor of 10 by purification for liquid scintillator and xenon gas. By combining the first and second phase data and applying the improved event selection, we obtained a preliminary lower limit for the neutrinoless double-beta decay half-life, T1/20ν>2.6×1025 yr at 90% C.L. We also present the prospects about current phase of KamLAND-Zen and next phases with upgrades.

Semi Empirical Formula For Neutrinoless Double Beta Decay

A Semi empirical formula for both phase space factor and Nuclear Matrix Element (NME) is developed for neutrinoless double beta decay, and the formula is used to compute the neutrinoless double beta decay half lives. Thecomputed half lives for neutrinoless double beta decay are compared with the corresponding experimental values and with those predicted by QRPA model. The semi empirical formula predictions are found to be in good agreement with experimental data. The semi empirical formula is used to predict neutrinoless double beta decay of various isotopes Ca, Ge, Se, Zr, Mo, Pd, Cd, Sn, Te, Xe, Nd and Sm that exhibiting single beta decay. As our semi empirical formula predictions agree with the experimental data we hope that the present work will be useful for the future experiments.

LHC dijet constraints on double beta decay

We use LHC dijet data to derive constraints on neutrinoless double beta decay. Upper limits on cross sections for the production of "exotic" resonances, such as a right-handed W boson or a diquark, can be converted into lower limits on the double beta decay half-life for fixed choices of other parameters. Constraints derived from run-I data are already surprisingly strong and complementary to results from searches using same-sign dileptons plus jets. For the case of the left-right symmetric model, in case no new resonance is found in future runs of the LHC and assuming $g_L=g_R$, we estimate a lower limit on the double beta decay half-live larger than $10^{27}$ ys can be derived from future dijet data, except in the window of relatively light right-handed neutrino masses in the range $0.5$ MeV to $50$ GeV. Part of this mass window will be tested in the upcoming SHiP experiment. We also discuss current and future limits on possible scalar diquark contributions to double beta decay that can be derived from dijet data.