SAIP2026

pnQRPA study to extract the axial-vector coupling strength from β-decay data

8 Jul 2026, 15:30

20m

Lecture Hall GH2 (University of the Western Cape)

Oral Presentation Track B - Nuclear, Particle and Radiation Physics Nuclear, Particle and Radiation Physics -1

Speaker

Mr Sifiso Mngonyama (University of the Western Cape)

Description

$\beta$-decay studies are important for searches for fundamental physics beyond the Standard Model [1, 2]. In particular, $\beta$-decay transition rates involve several crucial model-dependent variables such as nuclear matrix elements (NMEs), coupling constants, phase-space factors, etc, which may be calculated and compared with experiments. Of particular interest are NMEs and their relation to the weak axial-vector coupling strength ($g_{A}$). The NMEs contain information about the nuclear structure of the nuclei involved [3, 4]. The $g_{A}$ quantifies the strength of the spin-dependent part of the weak interaction in nucleons. For free nucleons, it’s value is determined by the partially conserved axial-vector current (PCAC) hypothesis, with $g_{A}=$ 1.27. However, in atomic nuclei, typically a quenched value is required that is usually attributed to multi-nucleon correlations [5]. One popular many-body technique used to investigate $g_{A}$ quenching and $\beta$-decay NMEs in medium to heavy nuclei is the proton–neutron quasiparticle random-phase approximation (pnQRPA) [3, 4, 5]. This work describes pnQRPA calculations to calculate the energy spectra of 12 odd-odd nuclei that were produced by Gamow-Teller (GT) $\beta^-/\mathrm{EC}$ transitions from even-even nuclei. The resulting wave functions were used to determine the quenching required for these cases, by matching theoretically predicted half-lives to experimental values.

References

[1] Alexander S. Barabash. Possibilities of future double beta decay experiments to investigate inverted and normal ordering region of neutrino mass. Frontiers in Physics, Volume 6 - 2018, 2019.

[2] J. Vergados, Hiroyasu Ejiri, and Fedor Simkovic. Theory of neutrinoless double beta decay. Reports on progress in physics. Physical Society (Great Britain), 75:106301, 09 2012.

[3] Jouni Suhonen and Osvaldo Civitarese. Review of the properties of the 0 nuclear matrix elements. Journal of Physics G: Nuclear and Particle Physics, 39:124005, 11 2012.

[4] Jouni Suhonen and Osvaldo Civitarese. Weak-interaction and nuclear-structure aspects of nuclear double beta decay. Physics Reports, 300(3):123–214, 1998.

[5] Jouni T. Suhonen. Value of the axial-vector coupling strength in and decays: A review. Frontiers in Physics, Volume 5 - 2017, 2017.

Presentation materials

SAIP_final_fixed_complete_source_final_compiled.pdf