What can we learn from recent $2\nu \beta \beta$ experiments?

Abstract

With recent measurements of the two neutrino double beta decay high precision electron spectra, combining with charge exchange or $\beta$-decay experimental data, we give severe constraints over the current nuclear many body calculations. Our calculation shows that QRPA approach can well reproduce the measured spectra for the two open shell nuclei, ${}^{82}$Se and ${}^{100}$Mo. For the closed shell nucleus ${}^{136}$Xe, QRPA can also reproduce the spectra with proper treatments. We also find that considering the high-lying state reduction, Nuclear Shell Model can also well reproduce the spectra as well as B(GT) strength under a unique quenched $g_A$. For ${}^{136}$Xe, we find that the flip of the sign for the decay strength will lead the spectra to go beyond HSD. These results call for future high precision measurement of charge-exchange reaction.

13 pages, 6 figures, comments are welcome, corrections and more details added

References in corpus (9)

• Phase space factors for double-$\beta$ decay
• $0\nu \beta \beta$ and $2\nu \beta \beta$ nuclear matrix elements, QRPA, and isospin symmetry restoration
• Average and recommended half-life values for two neutrino double beta decay
• Precision Analysis of the ${}^{136}$Xe Two-Neutrino $\beta \beta$ Spectrum in KamLAND-Zen and Its Impact on the Quenching of Nuclear Matrix Elements
• Overconstrained estimates of neutrinoless double beta decay within the QRPA
• Shell-model calculations of two-neutrino double-beta decay rates of ${}^{48}$Ca with GXPF1A interaction
• Single and low-lying states dominance in two-neutrino double-beta decay
• The first large-scale shell-model calculation of the two-neutrino double beta decay of ${}^{76}$Ge to the excited states in ${}^{76}$Se
• Investigation of the Lorentz invariance violation in two-neutrino double-beta decay