Beta-decay and double-beta-decay experiments measure neutrino masses by using as large a source mass as possible. At present, there are many of these experiments running, notable examples being KATRIN (beta-minus decay of tritium), ECHo (electron capture in holmium) and NEMO (double beta decays of several nuclear species). The first two experiments are clean experiments in the sense that they...
The observation of neutrinoless double beta decay would have far-reaching consequences for particle physics, as it would be a clear manifestation of lepton number violation and it would give a hint on the origin of neutrino masses. While searching for neutrinoless double beta decay, a significant amount of the two-neutrino double beta decay data has been collected by a number of experiments....
EXO-200 is a current generation experiment to search for neutrinoless double beta (0νββ) decay of 136Xe. It was the first of only a few detectors of this scale to run and operated between 2010 and 2018 at the underground Waste Isolation Pilot Plant (WIPP) in southern New Mexico, USA. EXO-200 used 200 kg of 80%-enriched liquid xenon in a single phase, cylindrical time projection chamber (TPC)...
The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for 0νββ decay that has been able to reach the one-tonne mass scale. The detector, located at the LNGS in Italy, consists of an array of 988 TeO2 crystals arranged in a compact cylindrical structure of 19 towers. CUORE began its first physics data run in 2017 at a base temperature of...
An experiment to study double-beta decay processes in $^{106}$Cd using a $^{106}$CdWO$_4$ crystal scintillator (mass 215.4 g) enriched in $^{106}$Cd to 66$\%$ is in progress in the DAMA/R&D setup at LNGS. The enriched crystal was placed in a close geometry with two CdWO$_4$ crystal scintillators in order to increase the detection efficiency to $\gamma$'s that can be emitted in the double-beta...
In my talk I will first give a brief review of the last results in the theoretical study of double-beta decay obtained by our Bucharest group. Next, I will focus on testing the Lorentz invariance violation (LIV) in double beta decay. I will present the calculation of the LIV perturbations in the energy electron spectra and in angular correlation between electrons and show possible...
Abstract: Among cold dark-matter candidates are low-mass neutral bosons. The existence of such pseudo-scalar particles has been proposed long ago by Peccei and Quinn to explain the spontaneous breaking of CP in the early Universe. In this talk we discuss a possible mechanism to explain for non-zero neutrino masses, which is based on the treatment of neutrino-axions interactions.From the known...
Reliable nuclear matrix elements play a crucial role in planning future neutrinoless double-beta-decay experiments, and in extracting the exciting new physics from them. Unfortunately, currently the nuclear matrix elements are not well constrained, and different many-body methods notably disagree on the values of them. Another open question is the possible need of quenching the axial-vector...
It is well known that the neutrino medium, such as the cosmic neutrino background, produces a tiny birefringence effect on electromagnetic waves. Recently, it was claimed that this effect may be enhanced by an additional presence of a plasma characterized by the electron plasma frequency. In our work, instead of considering the plasma, we consider a ordinary transparent refractive medium...
Experimental studies of charge-exchange nuclear and leptonic reactions are useful for evaluating nuclear matrix elements (NMEs) for double beta decays (DBDs). The sin-dipole (SD) NME is one of the major components of the DBD NME. The experimental SD giant resonance energy and the SD strength are shown to be closely related with pnQRPA NME. The NME is obtained by using the particle hole...
The ACCESS project (Array of Cryogenic Calorimeters to Evaluate Spectral Shapes) aims to establish a novel technique to perform precision measurements of forbidden beta-decays, whose spectral shape is a crucial benchmark for Nuclear Physics calculations and plays a pivotal role in Astroparticle Physics experiments. ACCESS will operate a pilot array of four tellurium dioxide crystals as...
Molybdenum-100 is one of the popular isotopes used to search for double beta decay and to study nuclear matrix elements. The half-lives of the two neutrino double beta decays of Mo-100 to the various excited states of Ru-100 were investigated with two samples of Mo-100-enriched molybdenum trioxide powders. The measurements were performed using an array of fourteen HPGe detectors, CAGe, located...
Extracting particle physics properties from neutrinoless double-beta (0nßß) decay, requires a detailed understanding of the involved nuclear structures. Still, modern calculations of the corresponding nuclear matrix elements (NMEs) differ by factors 2-3.
The high momentum transfer of Ordinary Muon Capture (OMC) provides insight into highly excited states similar to those that contribute...
Reliable nuclear matrix elements for the neutrinoless double-beta decay of Germanium, Molibdenum, Tellurium and Xenon are necessary to determine the physics reach of next generation experiments and to fully exploit their findings. In this talk I will present recent improvements in calculations with the nuclear shell model, one of the leading many-body methods to obtain these nuclear matrix...
Although the neutrinoless double-beta decay has not been experimentally proven yet, there is work undergoing to improve the theoretical description of the decay.
In this work, we computed the nuclear matrix elements using the shell model techniques and the electron phase-space factors for several nuclei of interest. The latter were computed using three different descriptions for the...
The reactor neutrino anomaly and $g_A$ “quenching” in neutrinoless double-β decay are two of the outstanding issues in nuclear physics. Measurement of the first-forbidden nonunique β decay of $^{137}$Xe can provide helpful input to both issues but is difficult to perform accurately. EXO-200 is a low-background neutrinoless double-β decay experiment that used close to 200 kg of $^{136}$Xe as a...
The spectrum-shape method has been proposed to determine the effective value of the axial-vector coupling constant, $g_A$ with the vector coupling constant, $g_v = 1$ in forbidden nonunique $\beta$ decays. $^{210}$Bi nuclear is the isotope of first nonunique forbidden beta decay, the shape function of which strongly depends on the $g_A$.
Due to the short half-life of the $^{210}$Bi, the...
nEXO is a proposed next-generation liquid xenon experiment to search for neutrino-less double beta decay (0νββ) of $^{136}$Xe. The experiment will use a 5-tonne liquid xenon (LXe) monolithic time projection chamber (TPC) with xenon enriched to 90% the isotope 136. While the nEXO design is validated by EXO-200, the larger detector will employ novel techniques to collect charge and scintillation...
The gamma-ray emissions from a radiopure cerium-bromide crystal with a mass of 4381 g were measured for a total of 497.4 d by means of high-resolution gamma-ray spectrometry in the HADES underground laboratory at a depth of 500 m.w.e.
Publikation: Phys. Rev. C 105, 045801 (2022)
Neutrinoless double-beta decay (0νββ) is a hypothetical rare nuclear transition. Its observation would provide an important insight about the nature of neutrinos (Dirac or Majorana particle) demonstrating that the lepton number is not conserved. BINGO aims to set the technological and conceptual grounds for future bolometric 0νββ experiments. It is based on a dual heat-light readout, i.e. a...
Neutrinoless double beta decay (0νββ) nuclear matrix elements (NME) are the object of many theoretical calculation methods, and are very important for analysis and guidance of a large number of experimental efforts. However, there are large discrepancies between the NME values provided by different methods. In this paper we propose a statistical analysis of the 48Ca 0νββ NME using the...
The nuclear matrix element of neutrinoless double-β decay is an essential input for determining the neutrino effective mass, if the half-life of this decay is measured. Reliable calculation of this nuclear matrix element has been a long-standing problem because of the diversity of the predicted values of the nuclear matrix element, which depends on the calculation method. In this study, we...
Precise calculations of nuclear matrix elements provide a solid foundation in order to extract relevant data from current and upcoming neutrinoless double-beta decay experiments. These searches are key to unveil the nature of neutrinos as well as to access physics beyond the Standard Model due to the violation of the lepton number conservation in neutrinoless double-beta decay.
In this...
The CUPID-Mo experiment, located in the Laboratoire Souterrain de Modane (France), is a demonstrator for the next generation 0νββ experiment CUPID. The experiment is an array of 20 enriched Li$_2$ $^{100}$MoO$_4$ bolometers and 20 Ge light detectors, working at 20 mK. The experiment has collected data from spring 2019 to summer 2020, for a total exposure of 2.71 kg.yr. Within this exposure,...
The SuperNEMO experiment is a one-of-a-kind detector searching for neutrinoless double beta decay (0νββ). The unique design of this heterogeneous detector takes advantage of the combination of 2034 drift cells operating in Geiger Mode (tracker) with 712 plastic scintillator modules (calorimeter) placed around a 6.3kg thin foil of Se-82 – the source of the double beta decay (DBD). This design...
CUPID-0 is a pilot experiment in scintillating cryogenic calorimetry for the search of neutrino-less double beta decay. 26 ZnSe crystals coupled to bolometric light detectors were operated continuously for two years. From its successful experience comes a demonstration of full alpha to beta/gamma background separation, the most stringent limit on the 82Se neutrino-less double beta decay, as...
As experiments searching for neutrinoless double beta decay are in the planning phase of a next generation with hopes to completely probe the inverted mass hierarchy, the need for reliable nuclear matrix elements, which govern the rate of this decay, is stronger than ever. Since a large discrepancy is found when computing this quantity with different nuclear models, a large unknown still...
Theoretical and experimental studies on the beta decays of the most prominent fission products in nuclear reactors are needed to unravel the source of the anomalies detected in the related anti-neutrino flux. One of these fission products, 92Rb, was recently studied for its beta decay to 92Sr by using large-scale nuclear shell-model (NSM) calculations to analyze the role of forbidden beta...
We will discuss possibilities of how to experimentally distinguish different mechanisms of $0\nu\beta\beta$-decay and thereby identify potential non-standard contributions. The different mechanisms possibly contributing to $0\nu\beta\beta$-decay are classified following an effective field theory approach. We find that when utilizing measurements of the leptonic phase space, i.e., the spectra...
The two-neutrino double-beta decay ($2\nu\beta\beta$-decay) process is attracting more and more attention from the physics community due to its potential to explain nuclear structure aspects of involved atomic nuclei and constrain new (beyond the Standard Model) physics scenarios. Topics of interest are energetical and angular distributions of the emitted electrons, which might allow the...
Many of today's double beta experiments go deep underground in order to reduce cosmic backgrounds.
Neutrons still can origin from the surrounding rock. This motivates the investigation of neutron induced reactions on the present materials with thermal but also with fast neutrons. For neutron cross section measurements it is necessary to know the applied neutron intensity.
TU Dresden runs a...
The SuperNEMO experiment was designed to search for neutrinoless double-beta decay. It is an improved version of a very successful predecessor experiment, NEMO-3. The detector uses a tracker-calorimeter technique to detect individual particles’ trajectories and energies. Energies are measured by a segmented calorimeter composed of polystyrene scintillator blocks.
The calorimeter will be...