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Title: The double-beta decay: Theoretical challenges

Abstract

Neutrinoless double beta decay is a unique process that could reveal physics beyond the Standard Model of particle physics namely, if observed, it would prove that neutrinos are Majorana particles. In addition, it could provide information regarding the neutrino masses and their hierarchy, provided that reliable nuclear matrix elements can be obtained. The two neutrino double beta decay is an associate process that is allowed by the Standard Model, and it was observed for about ten nuclei. The present contribution gives a brief review of the theoretical challenges associated with these two process, emphasizing the reliable calculation of the associated nuclear matrix elements.

Authors:
 [1]
  1. Department of Physics, Central Michigan University, Mount Pleasant, Michigan, 48859 (United States)
Publication Date:
OSTI Identifier:
22075834
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1498; Journal Issue: 1; Conference: Carpathian summer school of physics 2012, Sinaia (Romania), 24 Jun - 7 Jul 2012; Other Information: (c) 2012 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; 73 NUCLEAR PHYSICS AND RADIATION PHYSICS; DOUBLE BETA DECAY; MATRIX MATERIALS; NEUTRINOS; NUCLEAR MATRIX; NUCLEI; REST MASS; STANDARD MODEL

Citation Formats

Horoi, Mihai. The double-beta decay: Theoretical challenges. United States: N. p., 2012. Web. doi:10.1063/1.4768484.
Horoi, Mihai. The double-beta decay: Theoretical challenges. United States. doi:10.1063/1.4768484.
Horoi, Mihai. 2012. "The double-beta decay: Theoretical challenges". United States. doi:10.1063/1.4768484.
@article{osti_22075834,
title = {The double-beta decay: Theoretical challenges},
author = {Horoi, Mihai},
abstractNote = {Neutrinoless double beta decay is a unique process that could reveal physics beyond the Standard Model of particle physics namely, if observed, it would prove that neutrinos are Majorana particles. In addition, it could provide information regarding the neutrino masses and their hierarchy, provided that reliable nuclear matrix elements can be obtained. The two neutrino double beta decay is an associate process that is allowed by the Standard Model, and it was observed for about ten nuclei. The present contribution gives a brief review of the theoretical challenges associated with these two process, emphasizing the reliable calculation of the associated nuclear matrix elements.},
doi = {10.1063/1.4768484},
journal = {AIP Conference Proceedings},
number = 1,
volume = 1498,
place = {United States},
year = 2012,
month =
}
  • Assuming that the neutrinos are Majorana particles and the neutrinoless double beta (0{nu}{beta}{beta}) decay is observed, a reliable 0{nu}{beta}{beta} matrix element is necessary to decide the neutrino mass hierarchy and the minimum neutrino mass. Many nuclear structure techniques, including the shell model, are presently used to calculate these matrix elements. In the last few years one could see a slow convergence of these results, but not yet at a level of 20 several shell model effective interactions and varying other parameters, finding results in a range that spans about 20In this contribution we describe challenges for obtaining reliable shell modelmore » 0{nu}{beta}{beta} matrix elements, with emphasis to {sup 76}Ge and {sup 82}Se decays.« less
  • The main features of the Fermi interaction necessary for an understanding of the theoretical problems connected with double beta decay are summarized. The phenomenon of double beta decay is discussed from both the theoretical and experimental point of view, taking into account the possible improvement of present results. Problems connected with the mass and structure of the nuclei are presented. Experimental results on double beta decay are summarized. No conclusive evidence was obtained in favor of, or against, double beta decay without emission of neutrinos. (M.C.G.)
  • The sizes of tracks of events of neutrinoless double-beta decay in a Germanium detector depend on particle physics and nuclear physics parameters such as neutrino mass, right-handed current parameters, etc., and nuclear matrix elements. In this paper for the first time Monte Carlo simulations of neutrino-accompanied (2{nu}{beta}{beta}) and neutrinoless double-beta decay (0{nu}{beta}{beta}) events, and of various kinds of background processes such as multiple and other {gamma} interactions are reported for a Ge detector. The time history of the evolution of the individual events is followed and the sizes of the events (partial volumes in the detector inside which the energymore » of the event is released) are investigated. Effects of the angular correlations of the two electrons in {beta}{beta} decay, which again depend on the above nuclear and (for 0{nu}{beta}{beta} decay) on particle physics parameters, are taken into account and have been calculated for this purpose for the first time on basis of the experimental half-life of {sup 76}Ge and of realistic nuclear matrix elements. The sizes determine, together with the location of the events in the detector, the pulse shapes to be observed. It is shown for {beta}{beta} decay of {sup 76}Ge, that {beta}{beta} events should be selectable with high efficiency by rejecting large size (high multiplicity) {gamma} events. Double-escape peaks of similar energy of {gamma} lines show concerning their sizes similar behavior as 0{nu}{beta}{beta} events, and in that sense can be of some use for corresponding 'calibration' of pulse shapes of the detector. The possibility to distinguish {beta}{beta} events from {gamma} events is found to be essentially independent of the particle physics parameters of the 0{nu}{beta}{beta} process. A brief outlook is given on the potential of future experiments with respect to determination of the particle physics parameters <m{sub {nu}}>,<{lambda}>,<{eta}>.« less
  • The calculations of nuclear matrix elements, corresponding to nuclear double beta decay transitions, rely upon several approximations. The impact of these approximations upon final estimations of the nuclear matrix elements is illustrated. We pay attention to mean field (symmetry violations) and to approximate diagonalizations (pn-QRPA, renormalized pn-QRPA and fully renormalized pn-QRPA)
  • Investigation of neutrinoless double-beta (2{beta}0{nu}) decay is presently being considered as one of the most important problems in particle physics and cosmology Interest in the problem was quickened by the observation of neutrino oscillations. The results of oscillation experiments determine the mass differences between different neutrino flavors, and the observation of neutrinoless decay may fix the absolute scale and the hierarchy of the neutrino masses. Investigation of 2{beta}0{nu} decay is the most efficient method for solving the problem of whether the neutrino is a Dirae or a Majorana particle, Physicists from the Institute of Theoretical and Experimental Physics (ITEP, Moscow)more » have been participating actively in solving this problem. They initiated and pioneered the application of semiconductor detectors manufactured from enriched germanium to searches for the double-beta decay of {sup 76}Ge. Investigations with {sup 76}Ge provided the most important results. At present, ITEP physicists are taking active part in four very large projects, GERDA. Majorana, EXO, and NEMO, which are capable of recording 2{beta}0{nu} decay at a Majorana neutrino mass of <m{sub {nu}}> {approx} 10{sup -2} eV.« less