Nuclear Theory·nucl-th

Wednesday·July 30, 2025

10 papers—2 primary·8 cross-listed

01
Two-neutrino $β β$ decay to excited states at next-to-leading order
Daniel Castillo🇪🇸 · Dorian Frycz🇪🇸 · Beatriz Benavente🇪🇸 · Javier Menéndez🇪🇸
We study two-neutrino double-beta decay ( $2 ν β β$ ) into first-excited $0_{2}^{+}$ states of nuclei used in $β β$ decay experiments, including $^{76}$ Ge, $^{82}$ Se, $^{130}$ Te, and $^{136}$ Xe. We calculate the corresponding nuclear matrix elements (NMEs) within the nuclear shell model, using various Hamiltonians that describe well the spectroscopy of the initial and final nuclei. We evaluate the next-to-leading order (NLO) long-range NMEs recently introduced within chiral effective field theory, keeping three terms in the expansion of the energy denominator. In most cases, NLO contributions to the half-life are below 5%, but they can significantly increase due to cancellations in the leading-order Gamow-Teller NME. A detailed analysis in terms of nuclear deformation, including triaxiality, indicates that larger deformation differences between the initial and final states generally lead to smaller NMEs, but the seniority structure of the states also plays a relevant role. The lower range of our predicted half-lives, with uncertainties dominated by the nuclear Hamiltonian used, are slightly longer than the current experimental limit in $^{76}$ Ge and consistent with the very recent half-life indication in $^{82}$ Se.
nucl-thhep-exhep-phnucl-exPLB(2026)·3 citations
02
Constraining neutron-proton effective mass splitting through nuclear giant dipole resonance within transport approach
Yi-Dan Song🇨🇳 · Min-Si Luo🇨🇳 · Rui Wang🇨🇳 · Zhen Zhang🇨🇳 · Yu-Gang Ma🇨🇳
Based on the Boltzmann-Uehling-Uhlenbeck equation, we investigate the effects of the isovector nucleon effective mass $m_{v, 0}^{*}$ and the in-medium nucleon-nucleon cross section $σ^{*}$ on the isovector giant dipole resonance~(IVGDR) in $^{208} Pb$ , employing a set of representative Skyrme energy density functionals. We find that the energy-weighted sum rule $m_{1}$ of the IVGDR is highly sensitive to $m_{v, 0}^{*}$ and only mildly dependent on $σ^{*}$ , while the width $Γ$ of the IVGDR is primarily governed by $σ^{*}$ with a moderate sensitivity to $m_{v, 0}^{*}$ . From a Bayesian analysis of both $m_{1}$ and $Γ$ , we infer the isovector effective mass $m_{v, 0}^{*} / m$ = $0.73 1_{- 0.023}^{+ 0.027}$ , where $m$ is the bare nucleon mass. Furthermore, by incorporating the isoscalar effective mass $m_{s, 0}^{*} / m = 0.820 \pm 0.030$ , extracted from the isoscalar giant quadrupole resonance in $^{208} Pb$ , the linear neutron-proton effective mass splitting coefficient at saturation density $ρ_{0}$ is determined to be $Δ m_{1}^{*} (ρ_{0}) / m = 0.20 0_{- 0.094}^{+ 0.101}$ .
nucl-thnucl-exPRC(2025)·3 citations

Affiliations

first authorsco-authorsvia INSPIRE

Two-neutrino ββ decay to excited states at next-to-leading order

Constraining neutron-proton effective mass splitting through nuclear giant dipole resonance within transport approach

Affiliations

Two-neutrino $β β$ decay to excited states at next-to-leading order