arXiv subjects

Jakub Wysocki

Publications and source records attributed to Jakub Wysocki.

2 recordsLinked to original sources

arXiv2026

Influence of configuration-interaction on isospin impurities and isospin symmetry breaking corrections to superallowed $0^+\rightarrow 0^+$ beta decays

The symmetry-conserving density functional theory (DFT)-based no-core configuration-interaction (DFT-NCCI) framework is applied for the first time to investigate the impact of configuration interaction (CI) on the Coulomb (isospin) impurity, $α_{\rm C}$, in the ground and excited states of $^{10}$C, $^{10}$B, and $^{14}$N, as well as on the isospin-symmetry-breaking (ISB) correction to the superallowed $0^+ \rightarrow 0^+$ $β$ decay of $^{10}$C. We demonstrate, among other findings, that within the DFT-NCCI framework CI has a negligible effect on the ground-state isospin impurities, which are dominated by a single doorway state. In contrast, CI significantly modifies the impurities in excited states, including the isobaric analogue $I=0^+,\,T=1$ state in $^{10}$B. Hence, it also has a non-negligible impact on the ISB correction to the superallowed $β$ decay of $^{10}$C. Our calculations yield $\barδ_{\rm C}=0.45(4)\%$ when the Coulomb interaction is taken as the sole source of ISB, and $\barδ_{\rm ISB}=0.46(6)\%$ when short-range charge-symmetry-breaking (CSB) terms are included in addition. Hence, no statistically significant dependence of the ISB correction on the short-range CSB interaction is observed for this decay. Comparison with our previous results reveals a strong sensitivity to the nuclear symmetry energy, which governs the strength of the isospin-restoring force and whose value in finite nuclei remains difficult to constrain because of its intricate dependence on the momentum-dependent terms of the effective interaction.

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arXiv2026

Skyrme SV density-functional analysis of the $2νββ$ decay in $^{76}$Ge

We present a theoretical study of the two-neutrino $0^+ \rightarrow 0^+$ double beta decay of $^{76}$Ge within the No-Core Configuration-Interaction framework based on the Skyrme SV density functional. We analyze three allowed decay scenarios distinguished by the $[n,m] \equiv [(νg_{9/2})^n, (πg_{9/2})^m]$ occupancy of the $0g_{9/2}$ intruder orbital, which remains conserved to high precision, as well as by the triaxiality of the daughter nucleus. The resulting $2νββ$ nuclear matrix element is found to depend strongly on the scenario. For the energetically favored $[4,2]$ occupancy, we obtain $|\mathcal{M}^{2ν}| = 0.069(7)$~MeV$^{-1}$. For the $[6,0]$ occupancy, the matrix element further depends on the triaxiality parameter $γ$ of the two coexisting, closely lying minima in $^{76}$Se, yielding $|\mathcal{M}^{2ν}| = 0.040(4)$~MeV$^{-1}$ at $γ= 17.7^\circ$ and $|\mathcal{M}^{2ν}| = 0.22(2)$~MeV$^{-1}$ at $γ= 41.9^\circ$. The latter result is consistent with the empirical value reported by A. S. Barabash, $|\mathcal{M}^{2ν}| = 0.204(14)$~MeV$^{-1}$, while the two former results are comparable to existing calculations based on energy-density-functional frameworks. Our calculations reveal challenges in the precise determination of the $|\mathcal{M}^{2ν}|$ for the $^{76}$Ge decay. The structural complexity, triaxiality, and shape coexistence identified in the analyzed nuclei imply a strong sensitivity to fine details of the interaction and configuration mixing. This, in turn, explains the difficulties in theoretical modeling of the $|\mathcal{M}^{2ν}|$ matrix elements for the $^{76}$Ge decay, which vary by almost an order of magnitude in the available literature.

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