In the global landscape of neutrinoless double beta ($0νββ$) decay search, the use of semiconductor germanium detectors provides many advantages. The excellent energy resolution, the negligible intrinsic radioactive contamination, the possibility of enriching the crystals up to 88% in the $^{76}$Ge isotope as well as the high detection efficiency, are all key ingredients for highly sensitive $0νββ$ decay search. The MAJORANA and GERDA experiments successfully implemented the use of germanium (Ge) semiconductor detectors, reaching an energy resolution of $2.53 \pm 0.08$ keV at the Q$_{ββ}$ and an unprecedented low background level of $5.2 \times 10^{-4}$ cts/(keV$\cdot$kg$\cdot$yr), respectively. In this paper, we will review the path of $0νββ$ decay search with Ge detectors from the original idea of E. Fiorini et al. in 1967, to the final recent results of the GERDA experiment setting a limit on the half-life of $^{76}$Ge $0νββ$ decay at $T_{1/2} > 1.8 \times 10^{26}$ yr (90\% C.L.). We will then present the LEGEND project designed to reach a sensitivity to the half-life up to $10^{28}$ yr and beyond, opening the way to the exploration of the normal ordering region.
Liquid scintillator experiments for neutrinoless double beta decay search have high sensitivity based on the ultra low background environment and high scalability. This paper describes an overview of current ongoing projects KamLAND-Zen and SNO+.
The search for neutrinoless double beta decay ($0νββ$) is one of the key experiments for determining unresolved properties of neutrinos. Experimental observation of $0νββ$ would provide a clear demonstration of the Majorana nature of neutrinos and a lepton number violating process in particle physics. This report is a brief review describing the $0νββ$ process and its significance. The detector technologies used in the present and proposed $0νββ$ experiments are compared among their recent experimental results. Moreover, the sensitivities for $0νββ$ discovery in a number of present and propose…
Probing neutrinoless double beta decay is one of the primary goals for SNO+, SNOLAB's multi-purpose neutrino detector. In order to achieve this goal the SNO detector has been adapted so that it can be filled with Te-loaded liquid scintillator. During the initial double beta phase the target loading is 0.3% natural Te, which equates to $\sim790$ kg of double beta isotope. Estimating the sensitivity to neutrinoless double beta decay requires a well understood background model. For SNO+ this is provided by a comprehensive study considering all possible background contributions, whether they origi…
Environmental radioactivity is a dominant background for rare decay search experiments, and it is difficult to completely remove such an impurity from detector vessels. We propose a scintillation balloon as the active vessel of a liquid scintillator in order to identify this undesirable radioactivity. According to our feasibility studies, the scintillation balloon enables the bismuth--polonium sequential decay to be tagged with a 99.7\% efficiency, assuming a KamLAND (Kamioka Liquid scintillator AntiNeutrino Detector)-type liquid scintillator detector. This tagging of sequential decay using al…
This paper reviews the current status and future outlook of neutrinoless double beta decay searches, which try to provide an answer to the fundamental question of whether neutrinos are Dirac or Majorana particles.
Results of the experiment on investigation of Germanium-76 double beta decay. Experimental data of Heidelberg-Moscow collaboration November 1995 - August 2001
This paper presents a review of the search for neutrinoless double beta decay of $^{76}$Ge with emphasis on the recent results of the GERDA experiment. It includes an appraisal of fifty years of research on this topic as well as an outlook.
Of the many extensions to the standard model that could possibly generate neutrino mass, most necessitate the neutrino being a Majorana fermion. If this is the case, the rare process of neutrinoless double beta decay is predicted with half lives greater than about $10^{25}$ years. Many current and future experiments look for this decay by identifying a summed double beta energy at the Q value of the decay, but adding energy and angular measurements of the individual betas allows the underlying decay mechanism to be probed. A novel nano-tracking detector based on a clever combination of thin fi…
We consider perturbative one loop QCD corrections to the light neutrino contribution to neutrinoless double beta decay and find large enhancement to the rate. QCD corrections also generate structures which mimic new physics contributions usually considered. Within some approximations, the net effect seem to almost saturate the experimental limits, and therefore seems to implt that this is all there is to neutrinoless double beta decay.
In the Standard Model the total lepton number is conserved. Thus, neutrinoless double-beta decay, in which the total lepton number is violated by two units, is a probe of physics beyond the Standard Model. In this review we consider the basic mechanism of neutrinoless double-beta decay induced by light Majorana neutrino masses. After a brief summary of the present status of our knowledge of neutrino masses and mixing and an introduction to the seesaw mechanism for the generation of light Majorana neutrino masses, in this review we discuss the theory and phenomenology of neutrinoless double-bet…
SNO+ is a large multipurpose neutrino detector situated 2km underground at SNOLAB in Sudbury, Canada. It reuses the structure of the SNO experiment with numerous infrastructure upgrades and with heavy water replaced by ultra-pure liquid scintillator. The detector will be loaded with 0.5% natural tellurium in order to search for neutrinoless double beta decay ($0νββ$). The expected sensitivity after 5 years of data taking is T$^{0ν} _{1/2} > 1.9 \times 10^{26}$ years (90% CL). A future increase in loading could achieve a sensitivity of ${\sim}10^{27}$ years.
The detection of neutrinoless double-beta decay will establish the Majorana nature of neutrinos. In addition, if the nuclear matrix elements of this process are reliably known, the experimental lifetime will provide precious information about the absolute neutrino masses and hierarchy. I review the status of nuclear structure calculations for neutrinoless double-beta decay matrix elements, and discuss some key issues to be addressed in order to meet the demand for accurate nuclear matrix elements.
We discuss the contribution of right-handed neutrinos (RHNs) to the effective neutrino mass of the neutrinoless double beta decay within the minimal type-I seesaw model using the intrinsic seesaw relation of neutrino mass and mixing parameters and the relative mass dependence of the nuclear matrix elements. In the viable parameter space, we find the possibilities of both the enhancement and cancellation to the effective neutrino mass from RHNs. The bounds on the parameter space of the RHNs can be determined with the effective neutrino mass extracted from neutrinoless double beta decay experime…
The search for neutrinoless double-beta decay is important in determining the Majorana nature of the neutrino, and also in establishing if lepton number is violated. In this work, we combine the published data from five independent neutrinoless double-beta decay experiments: CUORICINO, EXO, GERDA, KamLAND-Zen and NEMO-3. As these experiments use different isotope sources, the relative signal normalisation between them depends on the Nuclear Matrix Element (NME) calculations used. The combined limits for the Majorana neutrino mass for 5 different NME models range from 130-310 meV. The combined …
Recent neutrino experiment results show a preference for the normal neutrino mass ordering. The global efforts to search for neutrinoless double beta decays undergo a broad gap with the approach to the prediction in the three-neutrino framework based on the normal ordering. This research is intended to show that it is possible to find a neutrinoless double beta decay signal even with normal ordered neutrino masses. We propose the existence of a light sterile neutrino as a solution to the higher effective mass of the electron neutrino expected by the current experiments. A few short-baseline os…
We investigate the half-life expectations for neutrinoless double beta decay by applying statistical distributions of neutrino mixing observables, neutrino mass constraints from cosmology and nuclear matrix elements. The analysis is performed in the standard scenario of active Majorana neutrino exchange, when light sterile neutrinos are added, and within TeV-scale left-right symmetric frameworks. The latter two cases correspond to a modified phenomenology of double beta decay for a normal and inverted mass ordering, and thus different discovery potential for future experiments.
We review the potential to probe new physics with neutrinoless double beta decay $(A,Z) \to (A,Z+2) + 2 e^-$. Both the standard long-range light neutrino mechanism as well as short-range mechanisms mediated by heavy particles are discussed. We also stress aspects of the connection to lepton number violation at colliders and the implications for baryogenesis.
Interactions that manifest themselves as lepton number violating processes at low energies in combination with sphaleron transitions typically erase any preexisting baryon asymmetry of the Universe. In this article, we discuss the constraints obtained from an observation of neutrinoless double beta decay in this context. If a new physics mechanism of neutrinoless double beta decay other than the standard light neutrino exchange is observed, typical scenarios of high-scale baryogenesis will be excluded unless the baryon asymmetry is stabilized via some new mechanism. We also sketch how this con…
We discuss a mechanism of neutrinoless double beta decay, where neutrinos of different flavours come into play. This is realized by effective flavour-violating scalar interactions. As one consequence, we find that within the normal mass ordering the neutrino effective mass may no longer vanish due to contributions from other flavours. We evaluate the necessary nuclear matrix elements, consider the interference between the standard diagram and the new scalar one, and analyze a UV-complete model that realizes the scalar interaction. Tests of the complete model are possible at colliders and futur…
Addendum to: QRPA uncertainties and their correlations in the analysis of neutrinoless double beta decay
在以前的文章[Phys. Rev. D 79，053001（2009）]中，我们在准粒子无规相位近似（QRPA）中估计了与无中微子双β衰变（0 nu β β）的核矩阵元（NME）相关的不确定性。这种估计包括最近对NME的独立计算，因此仍然可以提供核模型不确定性的公平代表。在这种情况下，我们比较了Ge-76中0 nu β β衰变的声明与最近在Ge-136和其他核中的负结果，并推断了在90% C. L.时允许或排除的寿命范围。我们还强调了一些问题，应加以解决，以适当地比较和结合来自不同的0 nu β β衰变候选核的结果。
We study the impact of new physics contributions to neutrinoless double beta decay arising from right-handed current in comparison with the standard mechanism. If the light neutrinos obtain their masses from Type-II seesaw within left-right symmetric model, where the Type-I contribution is suppressed to negligible extent, the right-handed PMNS matrix is the same as its left-handed counterpart, making it highly predictable and can be tested at next-generation experiments. It is very attractive, especially with recent cosmological constraint favoring the normal hierarchy under which the neutrino…
