Motivated by recent experimental developments, the Pomeron constituent quark model (Pom-CQM) of the $\gamma +N\to J/\psi +N$ reaction of Lee et al. [Eur. Phys. J. A 58, 252 (2022)] and Sakinah et al. [Phys. Rev. C 109, 065204 (2024)] is applied to predict the exclusive $J/\psi$ photoproduction on nuclei $\left(A\right)$. Within the multiple scattering theory, the calculations are performed by including the impulse amplitude $T_{J/\psi A,\gamma A}^{\mathrm{IMP}}$ and the $J/\psi$-nucleus final state interaction (FSI) amplitude $T_{J/\psi A,\gamma A}^{\mathrm{FSI}}$. For the deuteron target, $T_{J/\psi d,\gamma d}^{\mathrm{IMP}}$ is calculated exactly using the wave function generated from the realistic nucleon-nucleon potentials. It is found that, near the threshold region, the $J/\psi$ photoproduction cross sections depend sensitively on the $d$ state of the deuteron wave function. The FSI amplitude $T_{J/\psi A,\gamma A}^{\mathrm{FSI}}$ is calculated using the first-order optical potential constructed from the $J/\psi \text{−}N$ scattering amplitude generated from the employed Pom-CQM. It turns out that the FSI has significant effects in the large momentum-transfer region. By using the conventional fixed scatter approximation (FSA) and the nuclear form factors from the variational Monte Carlo (VMC) calculations of Lonardoni et al. [Phys. Rev. C 96, 024326 (2017)], the cross sections of the $J/\psi$ photo production on ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$ are also predicted for future experimental investigations at Jefferson Lab and the Electron-Ion Collider.

We explore the density variation of the correlation coefficient of the key parameters of the nuclear equation of state (EoS) with the bulk and crustal properties of neutron stars. The analysis was performed using two diverse sets of nuclear effective interaction theories based on the nonrelativistic Skyrme Hartree-Fock model and the relativistic mean field model. We find that the commonly studied EoS parameters, namely the isoscalar incompressibility of symmetric nuclear matter $K\left(\rho \right)$ and the isovector slope of symmetry energy $L\left(\rho \right)$, reveal consistently maximum correlation with the radius, tidal deformability, and moment of inertia, all around twice the saturation density. We find even tighter and more robust correlations beyond the saturation density for constructed parameter $\eta ={\left[K{L}^2\right]}^{1/3}$, allowing the possibility to impose stringent constraints on high-density $K\left(\rho \right)$ and $L\left(\rho \right)$. Extensive correlation analysis of the EoS parameters with the radius and tidal deformability bounds from gravitational wave events and recent pulsar observations allow us to provide reliable constraints on the central values of $K\left({\rho }_0\right)\approx 240\mathrm{MeV}$ and $L\left({\rho }_0\right)\approx 48\mathrm{MeV}$ at saturation density and $K\left(1.6{\rho }_0\right)\approx {332}_{-50}^{+88}\mathrm{MeV}$ and $L\left(1.6{\rho }_0\right)\approx {122}_{-18}^{+26}\mathrm{MeV}$ at 1.6 times the saturation density. The crust-core transition density and the crustal fraction of moment of inertia are shown to correlate moderately with $L\left(\rho \right)$ and $\eta \left(\rho \right)$ near the subsaturation density.

Recent measurements of the $E2$ transition rate from the ground state to the first $2^{+}$ excited state of the proton dripline nucleus ${}^{36}\mathrm{Ca}$ show an unusual pattern when compared to its isotopic neighbor ${}^{38}\mathrm{Ca}$: despite having a higher $E_x\left(2_1^{+}\right)$ excitation energy, the $B(E2;0_1^{+}\to 2_1^{+})$ rate in ${}^{36}\mathrm{Ca}$ is larger. The question that naturally arises is to what extent this observation can be attributed to the unbound character of the $2_1^{+}$ state. To understand the influence of the continuum space on the low-energy properties of ${}^{36}\mathrm{Ca}$, we carried out Gamow shell model calculations that can account for the continuum coupling effects associated with the occupation of unbound $fp$ shells. We found that in the threshold $2^{+}$ state, ${}^{36}\mathrm{Ca}$ is spatially diffused, which impacts the observed $B\left(E2\right)$ trend.

In this work, two popular modern machine learning (ML) algorithms, the light gradient boosting machine (LightGBM, a decision tree-based algorithm) and the sparse variational Gaussian process (SVGP, a Bayesian method), are used to assess their performance in predicting the nuclear charge radius $R_{\mathrm{C}}$ by learning available experimental data. The training set consists of 820 $R_{\mathrm{C}}$ data points measured before 2013, and the validation set includes 110 data points measured up to 2021, and the most recently measured 24 data points are used to further evaluate the trained ML algorithms. With the consideration of 11 input features, both ML algorithms achieve competitive accuracy on the validation set, with the standard root-mean-square deviation (RMSD) of 0.0118 fm for SVGP and 0.0125 fm for LightGBM. The present work confirms that the feature of handling outliers for Hg isotopes proposed in previous work can significantly improve the performance of the Bayesian method, but it has almost no effect on the performance of LightGBM. Furthermore, the RMSD values obtained on the 24 newly measured nuclei are 0.0142 fm for SVGP and 0.0121 fm for LightGBM, once again demonstrating that the present ML algorithms with proper consideration of physical features can achieve competitive accuracy in predicting nuclear charge radii.

This paper extends the shell-model formalism for calculating the isospin-symmetry-breaking correction $\left({\delta }_C\right)$, which has been highly successful in studies of superallowed $0^{+}\to 0^{+}$ Fermi $\beta$ decays [Phys. Rev. C 77, 025501 (2008)], to the nuclear matrix elements of Gamow-Teller (GT) transitions. Despite the relaxation of the selection rules for GT transitions, it remains possible to recast ${\delta }_C$ into the isospin-mixing term $\left({\delta }_{C1}\right)$, induced by the effective Coulomb and nuclear charge-dependent forces, and the radial mismatch term $\left({\delta }_{C2}\right)$, which arises from differences between proton and neutron realistic wave functions. Consequently, all the refinement strategies for the individual correction terms, as considered in the aforementioned reference for superallowed $0^{+}\to 0^{+}$ Fermi $\beta$ decays, are also applicable to GT transitions. We demonstrate that the introduction of ${\delta }_C$ significantly improves the convergence with respect to spectator-nucleus states, compared to direct calculations of GT matrix elements. Additionally, when initial and final states belong to different isospin multiplets, only spectator states with lesser isospin contribute to ${\delta }_{C2}$, thereby disabling the counter term presented in Fermi transitions. Another unique aspect of the axial-vector process is the influence of the spin-orbit potential on ${\delta }_{C2}$ when spin-flip transitions, such as those connecting spin-aligned and -antialigned orbits, are present within the chosen model space. Furthermore, in the limit of two-level mixing, the dependence of ${\delta }_{C1}$ for GT transitions on the isospin-mixing amplitude begins at first order, whereas for Fermi transitions, it starts at second order. Therefore, both ${\delta }_{C1}$ and ${\delta }_{C2}$ could be distinctively substantial in GT transitions, and subsequently the higher-order correction terms [Phys. Rev. C 109, 014317 (2024)] which account for interference effects, are generally not negligible. These behaviors are in good agreement with our numerical calculations for various $p$- and $sd$-shell nuclei using phenomenological effective Hamiltonians and realistic Woods-Saxon radial wave functions.

Mid-weight $\alpha$-conjugate nuclei are predicted to possess exotic toroid like resonances with high angular momenta. The search for these states in ${}^{28}\mathrm{Si}^{*}$ is the main point of two published experimental investigations of the peripheral ${}^{28}\mathrm{Si}$ $+$ ${}^{12}\mathrm{C}$ reaction by Cao and collaborators and by Hannaman and collaborators. In this work, we develop a novel artificial intelligence (AI) based machine learning method utilizing the Gaussian Mixture Model (GMM) to analyze available experimental and theoretical data. We additionally study the reaction with the Hybrid $\alpha$-Cluster $\left(\mathrm{H}\alpha \mathrm{C}\right)$ model. In all the examined data, our results suggest the presence of underlying structure which is close to that predicted for toroidal states.

Based on Belle data, the structure around 1435 MeV and the role of the $\mathrm{\Sigma }\left(1380\right)$ resonance in the decay process ${\mathrm{\Lambda }}_c\to \mathrm{\Lambda }{\pi }^{-}{\pi }^{+}{\pi }^{+}$ are investigated. The $\mathrm{\Lambda }{\pi }^{\pm }$ invariant mass spectra are approximately reproduced by the contribution from the $\mathrm{\Sigma }\left(1385\right)$, modeled as a Breit-Wigner resonance combined with background. However, an additional contribution is required to account for the pronounced enhancement near 1435 MeV. To describe this structure, two scenarios are considered for the $\mathrm{\Sigma }\left(1435\right)$: one as a Breit-Wigner resonance with spin-parity $1/2^{-}$ described via effective Lagrangians, and the other as a rescattering effect arising from coupled-channel interactions. Specifically, the channels ${\overline{K}}^{0}p$, ${\pi }^0{\mathrm{\Sigma }}^{+}$, ${\pi }^{+}{\mathrm{\Sigma }}^0$, ${\pi }^{+}\mathrm{\Lambda }$, and $\eta {\mathrm{\Sigma }}^{+}$ are included for the positively charged mode, and $K^{-}n$, ${\pi }^0{\mathrm{\Sigma }}^{-}$, ${\pi }^{-}{\mathrm{\Sigma }}^0$, ${\pi }^{-}\mathrm{\Lambda }$, and $\eta {\mathrm{\Sigma }}^{-}$ for the negatively charged mode. The rescattering contributions are evaluated using the quasipotential Bethe-Salpeter equation approach. Simulated invariant mass spectra are generated and fitted to the experimental data. Both the Breit-Wigner and rescattering mechanisms provide reasonable descriptions of the enhancement near 1435 MeV. The rescattering approach naturally generates a cusp-like structure near threshold, which closely resembles the feature observed in the data. Furthermore, the inclusion of the $\mathrm{\Sigma }\left(1380\right)$ resonance with spin-parity $1/2^{-}$ significantly improves the fit in the low-energy region and further enhances the description near 1435 MeV through interference effects. These results underscore the essential roles of the two ${\mathrm{\Sigma }}^{*}(1/2^{-})$ states in accurately describing the invariant mass distributions in the decay ${\mathrm{\Lambda }}_c\to \mathrm{\Lambda }{\pi }^{+}{\pi }^{+}{\pi }^{-}$.

Muon-induced fission could be utilized as a probe to study the underlying dynamics of nuclear fission. The probability of muon attachment to the light asymmetric fission fragment is sensitive to fission dynamics, such as the timescale and friction of the fission event, charge asymmetry, and possibly the shape of the fission fragments. We focus on muonic atoms that are formed with actinide nuclei. A relativistic approach is employed, solving the Dirac equation for the muonic wave function in the presence of a time-dependent electromagnetic field generated by the fissioning nucleus. Computations are carried out on a three-dimensional Cartesian lattice with no symmetry assumptions. The results show a strong dependence of the attachment probability on the fission charge asymmetry and a more modest dependence on friction.

Based on the model of three-fluid dynamics (3FD), the global $\mathrm{\Lambda }$ polarization ($P_{\mathrm{\Lambda }}$) is calculated in $\mathrm{Au}+\mathrm{Au}$ collisions at 3 $\le \sqrt{s_{NN}}\le$ 9 GeV, in which high baryon density is achieved. Various contributions to $P_{\mathrm{\Lambda }}$ are considered: those from the thermal vorticity, meson field, thermal shear, and spin-Hall effect. Feed-down from higher-lying resonances is also taken into account. The results are compared with available data. Special attention is payed to the collision energies of $\sqrt{s_{NN}}=3$, 3.2, 3.5, 3.9, and 4.5 GeV, for which a thorough scan of the energy, rapidity, and centrality dependence of $P_{\mathrm{\Lambda }}$ is performed. The results for 3 GeV reasonably well reproduce the corresponding STAR data. While the results at $\sqrt{s_{NN}}=3.2$, 3.5, 3.9, and 4.5 GeV can be considered as predictions for results of measurements within the STAR fixed-target (STAR-FXT) program that are expected in the nearest future. It is predicted that a broad maximum of $P_{\mathrm{\Lambda }}$ is reached at $\sqrt{s_{NN}}\approx 3$–3.9 GeV, exact position of which depends on the centrality and width of the midrapidity range of observation. Impact of the meson-field, thermal-shear, and spin-Hall-effect contributions to $P_{\mathrm{\Lambda }}$ is also studied.

To capture the dynamics of macroscopic nonrelativistic fluids consisting of very many atoms, it is typically sufficient to truncate the gradient expansion at order zero, leading to ideal fluid dynamics, or at order one, leading to the Navier-Stokes theory. For mesoscopic fluids consisting of a small number of atoms, second-order corrections can become significant. We investigate here specifically superfluids at vanishing temperature and identify relevant second-order terms of quantum origin that contribute already in a static situation. The general form of these terms arises from an extension of the Gross-Pitaevskii theory. In the context of density functional theory, they are named after C. von Weizsäcker. We assess the influence of these terms on numerical solutions of second-order fluid dynamic equations for the expansion of a mesoscopic ultracold Fermi gas released from an anisotropic harmonic trap in two spatial dimensions.

We measure for the first time the differential photoproduction cross section $d\sigma /dt$ of the $a_2\left(1320\right)$ meson at an average photon beam energy of 8.5 GeV, using data with an integrated luminosity of 104 ${\mathrm{pb}}^{-1}$ collected by the GlueX experiment. We fully reconstruct the $\gamma p\to \eta {\pi }^{0}p$ reaction and perform a partial-wave analysis in the $a_2\left(1320\right)$ mass region with amplitudes that incorporate the linear polarization of the beam. This allows us to separate for the first time the contributions of natural- and unnatural-parity exchanges. These measurements provide novel information about the photoproduction mechanism, which is critical for the search for spin-exotic states.

Using an effective field-theoretical approach, we investigate the properties of weakly bound two-neutron halo nuclei (also known as Borromean nuclei) that do not support a low-energy $s$-wave core-neutron resonance. Extending the recently formulated effective field theory for weakly bound Borromean nuclei, we incorporate corrections arising from the effective range of neutron-neutron scattering and evaluate their impact on the mean-square radii and electromagnetic response. In particular, we compute the ratio of the matter and charge radii, the shape of the $E1$ dipole strength function, and the electric polarizability. Our results indicate that these corrections remain numerically small when the two-neutron separation energy of the Borromean nucleus is much less than 1 MeV.

We apply a variational ansatz based on neural networks to the problem of spin-$\frac{1}{2}$ fermions in a harmonic trap interacting through a short distance potential. We showed that standard machine learning techniques lead to a quick convergence to the ground state, especially in weakly coupled cases. Higher couplings can be handled efficiently by increasing the strength of interactions during “training”.

The region of $N\approx Z\approx 40$ has long been associated with strongly deformed nuclear configurations. The presence of this strong deformation was recently confirmed through lifetime measurements in $N\approx Z$ Sr and Zr nuclei. Theoretically, however, these nuclei present a challenge due to the vast valence space required to incorporate all necessary orbitals. Recent state-of-the-art predictions indicate a near axial prolate deformation for $N=Z$ and $N=Z+2$ nuclei between $N=Z=36$ and $N=Z=40$. In this work we investigate the shores of this island of deformation through a sub-barrier Coulomb excitation study of the $N=Z+4$ nucleus, ${}^{80}\mathrm{Sr}$. Extracting a spectroscopic quadrupole moment of $Q_s\left(2_1^{+}\right)=0.5_{-0.9}^{+0.8}e\mathrm{b}$, we find that ${}^{80}\mathrm{Sr}$ is inconsistent with significant axial prolate deformation with a significance of $1.5\sigma$. This result, albeit with a large uncertainty, indicates that the predicted region of strong prolate deformation around $N=Z=40$ is tightly constrained to the quartet of nuclei: ${}^{76,78}\mathrm{Sr}$ and ${}^{78,80}\mathrm{Zr}$.

Background: Radiative neutron capture on thulium, which is a monoisotopic element, plays a role in different applications such as nuclear astrophysics or nuclear burning environments. Considerable discrepancies—reaching 20%—exist between evaluations in the unresolved-resonance region. Furthermore, experimental data on statistical $\gamma$ decay in odd-odd rare-earth nuclei is scarce. There are still open questions about the systematics of the so-called scissors mode in the $M1$ photon strength function, especially in odd-odd nuclei.

Purpose: This work is focused on two main topics—deriving experimental ${}^{169}\mathrm{Tm}(n,\gamma )$ cross section and studying statistical $\gamma$ decay of ${}^{170}\mathrm{Tm}$, in particular properties of the scissors mode.

Methods: The capture experiments to obtain experimental cross section were performed at the Los Alamos Neutron Science Center using the time-of-flight technique and employing the Detector for Advanced Neutron Capture Experiments. Measured coincident $\gamma$-ray spectra were also compared with statistical simulations using the dicebox code to test different models of level density and photon strength functions.

Results: The capture cross section was determined from 1.8 eV to 0.97 MeV, the broadest neutron-energy range ever measured for this isotope. Several new resonances have been observed. The statistical $\gamma$ decay of ${}^{170}\mathrm{Tm}$ cannot be reproduced without a scissors mode resonance centered at $\approx 3.3\mathrm{MeV}$.

Conclusions: The measured cross section in the unresolved-resonance region is generally lower than the latest evaluations. The derived ${}^{169}\mathrm{Tm} s$-process abundance is expected to increase by a factor of 1.26, while the changes of the abundances of elements heavier than ${}^{169}\mathrm{Tm}$ are in the order of 0.2%. The scissors mode properties in ${}^{170}\mathrm{Tm}$ are similar to those deduced in previous analyses of neighboring nuclei ${}^{168}\mathrm{Er}$ and ${}^{166}\mathrm{Ho}$.

Proton and $\alpha$-particle emission spectra have been measured in ${}^4\mathrm{He}+{}^{58}\mathrm{Ni}$ and ${}^4\mathrm{He}+{}^{64}\mathrm{Ni}$ reactions at energies $\gtrsim 10$ MeV/nucleon to understand the complex interplay between the equilibrium and pre-equilibrium (PE) emission processes and effect of $N/Z$ asymmetry on them. Theoretical analyses of the experimental spectra were performed using the $\mathrm{TALYS}$ code, including contributions from both equilibrium or compound nuclear (CN), and PE components. While the $\alpha$-particle spectra aligned well with default $\mathrm{TALYS}$ predictions, the proton spectra showed significant deviations due to an over-prediction of the PE component. The relative contributions of CN and PE components were extracted from the energy spectra and compared for the two systems at different angles. The analyses showed a significantly higher PE fraction in the ${}^4\mathrm{He}+{}^{64}\mathrm{Ni}$ reaction compared to ${}^4\mathrm{He}+{}^{58}\mathrm{Ni}$, suggesting a link between the $N/Z$ asymmetry and PE emission. The present study provides crucial information in refining available theoretical models and offers key insights into the underlying reaction mechanisms.