Wed·Apr 9, 2025Wednesday·April 9, 2025

1. 01*

   Impact of newly measured $\beta$\nobreakdash-delayed neutron emitters around \myisoSimp{78}{Ni} on light element nucleosynthesis in the neutrino-wind following a neutron star merger

   A. Tolosa-Delgado🇪🇸 · J. L. Tain🇪🇸 · M. Reichert · A. Arcones🇩🇪 · M. Eichler · B. C. Rasco🇺🇸 · N. T. Brewer🇺🇸 · K. P. Rykaczewski🇺🇸 · R. Yokoyama🇯🇵 · R. Grzywacz🇺🇸 · I. Dillmann🇨🇦 · J. Agramunt🇪🇸 and 62 other authors

   Neutron emission probabilities and half-lives of 37 beta-delayed neutron emitters from 75Ni to 92Br were measured at the RIKEN Nishina Center in Japan, including 11 one-neutron and 13 two-neutron emission probabilities and 6 half-lives measured for the first time, which supersede theoretical estimates. These nuclei lie in the path of the weak r-process occurring in neutrino-driven winds from the accretion disk formed after the merger of two neutron stars, synthesizing elements in the A~80 abundance peak. The presence of such elements dominates the accompanying kilonova emission over the first few days and has been identified in the AT2017gfo event, associated with the gravitational wave detection GW170817. Abundance calculations based on over 17000 simulated trajectories describing the evolution of matter properties in the merger outflows show that the new data lead to an increase of 50-70 percent in the abundance of Y, Zr, Nb, and Mo. This enhancement is large compared to the scatter of relative abundances observed in old very metal-poor stars and is therefore significant in the comparison with other possible astrophysical processes contributing to light-element production. These results underline the importance of including experimental decay data for very neutron-rich beta-delayed neutron emitters into r-process models.

   nucl-exPRL(2025)·6 citations
2. 02*

   Entanglement in two-quasiparticle-triaxial-rotor systems: Chirality, wobbling, and the Pauli effect

   Q. B. Chen🇨🇳 · S. Frauendorf

   We investigate the entanglement in two-quasiparticle plus triaxial-rotor (PTR) model for the particle-hole configuration $\pi (1h_{11/2}{)}^1\otimes \nu (1h_{11/2}{)}^{-1}$, the particle-particle configuration $\pi (1h_{11/2}{)}^1\otimes \nu (1h_{11/2}{)}^1$, and two-proton particles configuration $\pi (1h_{11/2}{)}^2$ for different values of the triaxiality parameter. The entanglement between the angular momenta of the two quasiparticles and the total angular momentum is quantified by the three bipartite concurrences $\mathcal{C}$ of one type of angular momentum with the other two angular momenta and the area $\mathcal{F}$ of the triangle formed by the bipartite concurrences. Collective chiral and wobbling modes are identified for $\gamma >15^{\circ }$ via spin coherent state (SCS) maps and spin squeezed state (SSS) plots. Their entanglement increases from moderate values at the band head to near-maximal values at $I=20$. The area $\mathcal{F}$ of the chiral partners changes order as function of $I$ which reflects the crossing of the partner bands as a signature of chirality. For the $\pi (1h_{11/2}{)}^2$ configuration, the antisymmetrization required by the Pauli exclusion principle causes strong entanglement between the two protons, which significantly amplifies the area $\mathcal{F}$. For $\gamma <15^{\circ }$, the lowest bands become various uniformly rotating quasiparticle configurations, which have large values of $\mathcal{F}$ for all values $I$.

   ↳ nucl-thnucl-exPRC(2025)·6 citations
3. 03*

   Greedy Emulators for Nuclear Two-Body Scattering

   J. M. Maldonado · C. Drischler🇺🇸 · R. J. Furnstahl🇺🇸 · P. Mlinarić

   Applications of reduced basis method emulators are increasing in low-energy nuclear physics because they enable fast and accurate sampling of high-fidelity calculations, enabling robust uncertainty quantification. In this paper, we develop, implement, and test two model-driven emulators based on (Petrov-)Galerkin projection using the prototypical test case of two-body scattering with the Minnesota potential and a more realistic local chiral potential. The high-fidelity scattering equations are solved with the matrix Numerov method, a reformulation of the popular Numerov recurrence relation for solving special second-order differential equations as a linear system of coupled equations. A novel error estimator based on reduced-space residuals is applied to an active learning approach (a greedy algorithm) to choosing training samples ("snapshots") for the emulator and contrasted with a proper orthogonal decomposition (POD) approach. Both approaches allow for computationally efficient offline-online decompositions, but the greedy approach requires much fewer snapshot calculations. These developments set the groundwork for emulating scattering observables based on chiral nucleon-nucleon and three-nucleon interactions and optical models, where computational speed-ups are necessary for Bayesian uncertainty quantification. Our emulators and error estimators are widely applicable to linear systems.

   ↳ nucl-thhep-phnucl-exphysics.data-anPRC(2025)·17 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.