Neutrino-Mass Sensitivity and Nuclear Matrix Element for Neutrinoless Double Beta Decay

Abstract

Neutrinoless double beta decay (DBD) is a useful probe to study neutrino properties such as the Majorana nature, the absolute neutrino mass, the CP phase and the others, which are beyond the standard model. The nuclear matrix element (NME) for DBD is crucial to extract the neutrino properties from the experimental transition rate. The neutrino-mass sensitivity, i.e., the minimum neutrino-mass to be measured by the DBD experiment, is very sensitive to the DBD NME. Actually, the NME is one of the key elements for designing the DBD experiment. Theoretical evaluation for the DBD NME, however, is very hard. Recently experimental studies of charge-exchange nuclear and leptonic reactions have shown to be used to get single-β NMEs associated with the DBD NME. Critical discussions are made on the neutrino-mass sensitivity and the NME for the DBD neutrino-mass study and on the experimental studies of the single-β NMEs and nuclear structures associated with DBD NMEs.

Initial State Interaction for the 20Ne + 130Te and 18O + 116Sn Systems at 15.3 AMeV from Elastic and Inelastic Scattering Measurements

“…Promising experiments to establish the Majorana or Dirac nature of neutrinos are presently conceived of by searching for the neutrinoless double beta (0νββ) decay in nuclei such as 48 Ca, 76 Ge, 116 Cd and 130 Te, 136 Xe, with half-lives higher than 10 25 y [2][3][4]. The observation of the 0νββ decay would prove the Majorana nature of neutrinos, and the measurement of the half-life would allow for the determination of the effective neutrino mass, once appropriate nuclear matrix elements (NMEs) are accurately known [5][6][7].…”

Nuclear and Detector Sensitivities for Neutrinoless Double Beta-Decay Experiments

“…Since the axial-vector NMEs are strongly modified by the strong isobar (quark spin-isospin excitation) and other nonnucleonic correlations, we usually consider explicitly the renormalization coefficient g eff A , but the renormalization coefficient g eff V for the vector coupling should be well considered unless the models include all correlations and the medium effect [6][7][8]. The DBD NMEs are discussed in review articles on neutrino nuclear responses [6][7][8]. Theoretical works on DBD NMEs are discussed in reviews [9][10][11].…”

“…The present report is aimed at critically discussing the nuclear and detector sensitivities to search for the ultrarare DBD events associated with very small IH and NH masses. Critical discussions on DBD NMEs are presented elsewhere [8].…”

“…Nd has a large phase space factor because of the large Q value of 3.4 MeV and the large Z number of 60. Thus, m 0 ′ = 18 meV is half of the others [7,8]. The natural abundance, however, is only 5.6%, and enrichment is not easy (see Ref.…”

Enriched Crystal Scintillators for 2β Experiments

“…The investigation of neutrinoless electron capture with positron emission (0νεβ + ) and neutrinoless double positron emission (0ν2β + ) is one of possible ways to refine the mechanism of the decay due to the light ν mass or due to the right-handed currents admixture [25]. The development of experimental methods for the research of different 2β isotopes is highly required because of big uncertainties of the theoretical estimations for 0ν2β decay probability [26].…”