Single-particle and collective motions from nuclear many-body correlation (PCM2025)

Delta-isobar resonance effects on beta and double beta decays in medium heavy nuclei

6 Mar 2025, 12:00

20m

Main Lecture Hall (University of Aizu)

session #9

Speaker

Hiroyasu Ejiri (RCNP Osaka Univ.)

Description

Astro-$\nu$ interactions are studied by inverse $\beta$ decays and $\nu$-properties beynod the standard model are studied by neutrinoless double beta decays (0$\nu \beta \beta$). The $\beta$ and $\beta \beta$ nuclear matrix elements (NMES) consist mainly of the axial-vector spin ($\sigma$) isospin($\tau$) components, The delta-isobar ($\mathrm{\Delta }$) resonance excited by the quark $\tau \sigma$ excitation of nucleon in the nucleus is shown to quench the axial-vector components of NMEs. The effects are evaluated by using experimental energies and the strengths of the Gamow-Teller (nuclear $\tau \sigma$) resonsnces. The quenching effect is incorpolated by the effective axial-vector coupling around $g_A^{eff}$ $\approx$0.7$\pm$0.1 in units of $g_A$ for a free nucleon. Impact of the $\mathrm{\Delta }$ resonsnce on neutrino studues in nuclei is discussed.
H. Ejiri et al., Phys. Rep. 797, 1 2019, Phys. Rev. C105, L022501, C108, L11302 2023.

Presentation materials

25－3－6 Ejiri.pdf