Double beta decay

Abstract

Recent developments in the theoretical investigation of nuclear double-beta decay are reviewed. In particular, the neutrinoless mode is discussed in detail, since it is sensitive t o lepton number violation as predicted by gauge theories beyond the standard model and it is expected to give important information on the nature of the nenhinos and the weak interaction. Various approximations made in the theoretical treatment of neutrinoless and two-neutrino double beta decay are examined, and the present limits on the effective Majorana mass of the electron neutrino as well as the coupling constants of the right-handed leptonic current are presented.

Neutrinoless double-beta decay and physics beyond the standard model

“…One noticeable difference is that in [28,29] it was argued that the effect of short range correlations had been overestimated in earlier calculations. A recalculation of the nuclear matrix elements in [30], using the method proposed in [28], indeed led to an increase of (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40) % in the numerical values of the nuclear matrix elements. The latest calculation [25] also has short range matrix elements which are larger than those in [22] by similar factors.…”

“…Using s-wave approximation for the outgoing electrons and some assumptions according to [9,38] one has ME S+P S+P = −ME S+P S−P = − F (3)…”

Double Beta Decay: Theory, Experiment and Implications

“…When the 0ν decay is mediated by the right-handed weak current interaction the evaluation of the decay rate becomes more complicated, since many more terms must be included (see [2,3,20]). If the four-momentum of the virtual neutrino is q µ ≡ ω, q, the neutrino propagator contains…”

Overlap of quasiparticle random-phase approximation states for nuclear matrix elements of the neutrino-less double-βdecay

“…[1,2]), which are the aspects beyond the standard model. Neutrino physics is also very interesting for nuclear physics [3][4][5][6][7][8][9][10], because an accurate calculation of nuclear matrix elements of the neutrino-less double-β (0νββ) decay is necessary (e.g., Refs. [2,10]), along with the experimental half-life value of the initial nucleus in order to determine the neutrino mass in one of few methods.…”

“…We calculate the nuclear matrix elements of the 0νββ decay by employing the like-particle QRPA [16,17], which can be applied after the closure approximation [9,10,[18][19][20] is used. The advantage of this approach is that the intermediate states are free from the problem of how to treat the odd particle without any modification because they are states of even-even nuclei.…”