Double beta decay can occur near the bottom part of the mass valley where a given nucleus $(A,Z)$ has an adjacent nucleus $(A,Z+1)$ with higher mass while the nucleus $(A,Z+2)$ has a lower mass corresponding to an energy difference $\Delta E$. Double beta decay does exist as a second order decay process. The lifetimes estimated are typically of the order $T\approx 10^{20}$ y. Double beta decay carries a number of very intriguing aspects related to neutrino properties. Double beta decay has been observed both by geochemical methods and with counters.
Show AbstractHistory of the study of the double beta decay began in 1934 and is not finished yet. The physics of this process is closely connected with neutrino physics. The first experiments of the search for double beta decay were unsuccessful. Nowadays $2\beta 2\nu$ double beta decay was observed, but even modern experiments using a variety of detection methods could not confirm the existence of neutrinoless double beta decay, the possibility of which was theoretically demonstrated in 1937.
Show AbstractNeutrino oscillations is one of the main questions in modern physics of weak interactions. Neutrinos are uncharged leptons, i.e. particles of the Standard Model that do not participate in the strong interaction. They can be divided into three types (or, as they say, three flavors), in accordance with the classification of the charged leptons. This electron, muon and taon neutrinos. Oscillations are the processes of conversion from one type of neutrino to another. The oscillations occupy an extremely important place in modern neutrino physics, because they can answer the question of the neutrino mass existence. Recently, intensive experimental study of this phenomenon is conducted. A significant part of the modern neutrino experiments in some way connected with the study of neutrino oscillations.
Show AbstractNeutrinoless double beta decay is a type of double beta decay without emission of neutrinos in the final state: $A(Z,N)\rightarrow A(Z+2,N-2) + 2e^{-}$. The decay is possible when the lepton number is not conserved, ie, when neutrino $\nu_e$ is truly neutral Majorana particle. The change of the helicity of neutrino is also a necessary condition, it is directly linked to the issue of this particle’s mass. The average estimate of characteristic half-lives is more than $10^{23}$ years. The study of neutrinoless double beta decay is one of the most sensitive methods to verify the law of conservation of lepton numbers $L_e$. Search and observation of this type of decay can provide information about the nature of neutrino mass and about the existence of right-handed currents in the electroweak interactions. It is important for our understanding of the physics, and clarifies the question of the predominance of matter over antimatter, formed as a result of the Big Bang.
Show AbstractIn the article isotope $^{48}$Ca for observing double beta decay has been considered. Also launched experiment CANDLES and the experiment CARVEL, which is in the project stage, has been considered. Structure of detectors, their characteristics, methods of detection has been presented. Particular attention has been paid to the background processes for both experiments. Experimental sensitivity to double beta decay in the case CANDLES and simulation results for CARVEL has been presented.
Show AbstractDouble beta decay is a very rare nuclear decay and has double and neutrinoless modes of decay. This article describe the search of neutrinoless double beta decay in modern experiments NEMO, MOON, AMoRE. In these experiments are used different type of detectors and methods of registration, so the search for this decay have a different sensitivity to its half-life. The article also discussed the detectors, their features and prospects for their modernization for increasing sensitivity to neutrinoless beta decay.
Show AbstractThe article is dedicated to one of the most actual problems of modern nuclear physics - the study of the very rare decay mode known as double beta decay by the example of xenon-136 isotope. The article describes the principles of experimental observation of this decay mode with leading experiments in this field: EXO, NEXT and KamLAND-ZeN. There are schematics and description of the main parts of the experimental units. Also, the experimental results and their comparison are illustrated.
Show AbstractThe DCBA (Drift Chamber Beta-ray Analyzer) experiment is a project aimed at discovering of neutrinoless double beta decay in isotopes of Nd-150 and Se-82; that utilizes a track chamber with a Superconducting Solenoid Magnet (SCSM). Further search for $0\nu\beta\beta$ with increasing half-life ranging to the order of $10^{26}$~s is possible by means of the MTD (Magnetic Tracking Detector) project, which is a follow-up prototype based upon the DCBA experiment. Presently the development of the MTD project is halted due to the technical difficulty of obtaining Nd-150 of suf-ficient enrichment factor.
Show AbstractOne of the rarest nuclei decays known today is double $\beta$-decay. Double $\beta$-decay is studied using radiochemical and geochemical methods. It was discovered first for $^{130}$Te isotope and is confirmed by experiment for 9 more isotopes, the heaviest of wich is $^{238}$U. Double $e$-capture was discovered for $^{130}$Ba isotope. Of particular interest is the searching of neutrinoless double $e$-capture, as its observation allows to consider neutrino as a majorana particle.
Show AbstractDouble beta decay ($2\nu\beta\beta$) is a very rare nuclear process. The reason of the rarity of such decay is the second order forbiddance in the Standard Model of electroweak interactions for this process. Over the last 80 years two-neutrino double beta decay have been observed in 12 nuclei and their half-lives range from $10^{19}$ to $10^{24}$ years. This article is concerned with methods of theoretical calculations of half-lives of double beta decay. Also some attempts to describe the experimental data using empirical formulas are under consideration.
Show AbstractIn the article it is shown, why and how in quantum field theory neutrino masses of Dirac and Majorana types are occurs and how classical experiments are consistent with the assumption of real neutrality of the neutrino. A review of the academic literature on this topic is given.
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