We study open-charm hadrons production in pp and $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=200$ GeV using an improved multiphase transport (AMPT) model. Specifically, we show the transverse-momentum spectra and nuclear modification factors $R_{\mathrm{AA}}$ of $D^0$ mesons and ${\mathrm{\Lambda }}_c^{+}$ baryons, as well as the ${\mathrm{\Lambda }}_c^{+}/D^0$ ratio in pp and $\mathrm{Au}+\mathrm{Au}$ collisions. The results obtained from the AMPT model simulations are compared with the STAR experimental data and found to be consistent. We further investigate the ${\mathrm{\Lambda }}_c^{+}/D^0$ ratio by evaluating contributions from coalescence, fragmentation, and the combined $\mathrm{coalescence}+\mathrm{fragmentation}$ mechanisms, and we find that fragmentation alone underestimates the pronounced enhancement in $\mathrm{Au}+\mathrm{Au}$ relative to pp at low and intermediate $p_{\mathrm{T}}$, whereas the $\mathrm{coalescence}+\mathrm{fragmentation}$ mechanism reproduces the observed trend significantly better. These results indicate that coalescence plays a key role in charm-baryon productions and helps constrain the relative importance of different hadronization mechanisms in the ultrarelativistic nuclear collisions.

Nuclear isomers can have significant impacts on astrophysical nucleosynthesis processes, with recent efforts demonstrating that the population of isomeric states with different half-lives may require separate treatment in reaction networks to accurately capture the differences in heating or in identifiable electromagnetic signals. Several potential so-called “astromers” in tin and antimony isotopes near doubly magic ${}^{132}\mathrm{Sn}$ were identified and direct mass measurements of their ground and isomeric states were performed with the Canadian Penning Trap at Argonne National Laboratory's CARIBU facility, and their impact on astrophysical reaction rates and in reaction networks was calculated. It was found that ${}^{129g,m}\mathrm{Sn}$, with measured mass excesses of $-80593.2\left(25\right)$ and $-80557.4\left(25\right)$ keV, respectively, and an excitation energy of 35.8(35) keV, behaves as an astromer during neutron capture in the $i$-process and in the $r$-process.

Sensitivity studies have found that the ${}^{20}\mathrm{Ne}(\alpha ,p){}^{23}\mathrm{Na}$ reaction has a significant influence on supernovae Ia (SNIa) nucleosynthesis, but no previous measurements of the reaction cross section have been reported. Astrophysical reaction rate estimates have been based upon measurements of the inverse reaction, ${}^{23}\mathrm{Na}(p,\alpha ){}^{20}\mathrm{Ne}$, which ignores the contribution populating excited ${}^{23}\mathrm{Na}$ levels. In this paper, the first measurement of the ${}^{20}\mathrm{Ne}(\alpha ,p){}^{23}\mathrm{Na}$ reaction cross section is reported, and it is found that reactions populating excited ${}^{23}\mathrm{Na}$ levels are important to understanding the astrophysical reaction rate especially at temperatures above 2.0 GK, which are characteristic of hotter SNIa burning. Reaction cross sections populating both the ground state and the first excited ${}^{23}\mathrm{Na}$ state, astrophysical reaction rates, and uncertainties are reported.

The nature of the $\gamma$ band is studied for the soft triaxial even-even Xe isotopes ${}^{122–128}\mathrm{Xe}$ employing the five-dimensional collective Hamiltonian based on relativistic density functional theory. The theoretical calculations successfully reproduce the experimental staggering parameters $S\left(I\right)$ of the $\gamma$ band as well as the intraband and interband $B\left(E2\right)$ values for the ground-state band and $\gamma$ band. Pronounced $\gamma$ softness is shown across the Xe isotopes. Additionally, the analyses of angular momentum geometry via spin coherent state maps reveal that the even-spin states of the $\gamma$ band show large amplitude collective motion along $\gamma$ direction, while the odd-spin states exhibit wobbling mode with respect to the medium axis.

We simulate ultracentral collisions (impact parameter vector $|\vec{b}|<1$ fm) of deformed uranium-uranium nuclei at 500 MeV/nucleon via the isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model. Building upon these IBUU-generated simulations, we develop a convolutional orientation filter (COF) neural network model for the classification of reaction orientations. Based solely on the anisotropic flow of final-state particles, our COF model achieves high-precision event classification ($\approx 80\%$ validation accuracy), while also offering a novel approach for the accurate determination of the reaction plane. In addition to the linear relationship between $\langle v_2\rangle$ and ${\beta }_2$, we also find that the $\langle v_1^2\rangle$ signal is significantly enhanced when the major axis of the nucleus is oriented at approximately ${45}^{\circ }$ relative to the beam direction. This enhancement can be attributed to the significant reflection of nucleons or nuclear fragments induced by nuclear pressure. Additionally, the COF classifier also accurately characterizes the pion yields and ${\pi }^{-}/{\pi }^{+}$ ratios across different reaction orientations. Finally, we extend the discussion to include classification schemes at relativistic energies, utilizing simulations generated via the multiphase transport model in the string melting mode. Taken together, these findings provide robust support for the reliability of neural networks in evaluating the effects of symmetry energy in deformed nuclear collision reactions.

Accurate modeling of the density profile is essential for studying heavy-ion collisions (HICs) with a transport model. Within the framework of the quantum-molecular-dynamics–type model, a novel method for generating desired nuclear density distributions based on Fourier series expansion is proposed. This new initialization method is further incorporated into the ultrarelativistic quantum molecular dynamics model, and the bubblelike density distribution of ${}^{96}\mathrm{Ru}$ is constructed. Then, by simulating ${}^{96}\mathrm{Ru}+{}^{96}\mathrm{Ru}$ collisions at $E_{\mathrm{lab}}=1500\mathrm{MeV}/\mathrm{nucleon}$ with different equations of state (EoS) and initialization methods, the effects of the initial density distribution on the final state observables and the constrained information of EoS are analyzed. It is found that ${}^{96}\mathrm{Ru}$ nuclei with a bubble density profile lead to an increased maximum compression during the collision, which in turn enhances the collective flow. Moreover, a relatively stiff EoS with $K_0>280$ MeV is favored for the conventional Woods-Saxon-type density profile, whereas an EoS with $K_0=200–280\mathrm{MeV}$ is supported when a bubblelike density profile is employed. These results demonstrate that the initial nuclear density distribution plays a non-negligible role in dynamical observables and EoS constraints. The proposed method thus provides a powerful tool for constructing exotic profiles and investigating nuclear structure effects in HICs.

Based on the generalized reduced $R$-matrix theory, the $R$-matrix analysis code (RAC) program is employed to analyze all reaction channels associated with the ${}^7\mathrm{Be}$ system. The present calculations provide reliable evaluation data, which shows overall good agreement with available experimental measurements. Benefiting from the multichannel and multienergy fitting procedure, the resulting evaluation is internally self-consistent. The uncertainties of the evaluated cross sections and the covariance matrix are determined using the generalized least-squares method with rigorous uncertainty propagation theory. Compared with existing evaluated nuclear data libraries, the present evaluations are the most comprehensive for the ${}^7\mathrm{Be}$ system, effectively supplementing gaps in current evaluations. For the ${}^6\mathrm{Li}(\mathrm{p},{}^3\mathrm{He}){}^4\mathrm{He}$ reaction, the RAC analysis indicates that the resonance at $E_p \approx 1.8\mathrm{MeV}$ is predominantly associated with the $5/2^{-}$ state of ${}^7\mathrm{Be}$ compound nucleus. In addition, the astrophysical $S$ factor for the ${}^3\mathrm{He}({}^4\mathrm{He},\gamma ){}^7\mathrm{Be}$ reaction is calculated based on the present evaluation and the $S_{34}\left(0\right)$ is determined as $0.{563}_{-0.022}^{+0.022}\mathrm{keV}\mathrm{b}$ . These results are significant for future updates of evaluated nuclear data libraries and have important implications for nuclear astrophysics and the nucleosynthesis studies. The present analysis also highlights the limitations of existing experimental data for the ${}^7\mathrm{Be}$ system and the need for further high-precision measurements.

Nuclear $\beta$-decay half-lives are investigated by the neural network approach combined with a physically motivated $\beta$-decay half-life formula. This physics-information machine learning approach achieves better agreement with experimental half-lives than the sophisticated microscopic nuclear models and the empirical formulas. For the nuclei with half-lives less than 1 s, the neural network can describe the experimental half-lives about 1.62 times. It also effectively eliminates the nonphysical odd-even staggering of half-lives that is typically observed in traditional machine learning approaches and empirical formulas, leading to a more reliable description of nuclear $\beta$-decay half-lives. The extrapolation ability of the neural network is verified by newly measured half-lives as well.

We present measurements of the total and differential cross sections for near-threshold $J/\psi$ photoproduction obtained with the CLAS12 detector at the Thomas Jefferson National Accelerator Facility. The results are based on data collected during the fall 2018 and spring 2019 running periods, using electron beams with energies of 10.6 and 10.2 GeV, respectively, scattered off a liquid-hydrogen target. Near-threshold $J/\psi$ photoproduction offers a unique sensitivity to the strong interaction in the nonperturbative regime of quantum chromodynamics (QCD). The energy dependence of the cross section constrains the underlying $J/\psi$ production mechanisms, including multigluon exchange and potential baryonic excitations. Additionally, the $t$ dependence of the differential cross section can be related to the transverse spatial distribution of gluons in the proton, providing critical input for theoretical descriptions of the gluonic structure of the proton. An interpretation of the results in terms of the gluon content of the proton is presented, providing new experimental constraints on QCD-inspired models of the proton structure and the role of gluonic degrees of freedom in hadronic mass generation.

Excited states in the neutron-deficient nucleus ${}^{29}\mathrm{S}$ were populated in one-neutron knockout and several-nucleon removal reactions and studied using in-beam $\gamma$-ray spectroscopy. New excited states and $\gamma$-ray transitions were established using the Segmented Germanium Array SeGA and the $\gamma$-ray tracking array GRETINA. The new transitions observed in the highly dissipative tail of the parallel momentum distribution from one-nucleon knockout and in five- and nine-nucleon removal reactions were utilized to calculate mirror energy differences with ${}^{29}\mathrm{Al}$. Highly dissipative reactions further prove to be a valuable tool in populating excited states typically inaccessible in direct reactions. The relative populations of the states in ${}^{29}\mathrm{S}$ from the several-nucleon removal reactions were found to be consistent, suggesting for the first time that five-nucleon removal behaves predominately like statistical fragmentation.

In this study, a novel quantum-inspired Bayesian probability (QIBP) algorithm, informed by quantum dynamics, is proposed to improve the predictions of nuclear mass from theoretical models. Within the QIBP framework, residuals between the theoretical and experimental mass values are mapped into wave functions in Hilbert space. The corresponding potentials are obtained by solving the Schrödinger equation. Assuming that the residuals follow a Boltzmann distribution, the prior and likelihood probability density functions (PDFs) can be obtained from potentials. Finally, the Bayesian theorem is applied to derive the posterior PDF for estimating the target nuclear mass residuals. In global optimization, after employing the QIBP algorithm, the standard deviations of the WS4 model and the HFB model with the SLy4 parameter set are reduced from 0.273 and 5.250 MeV to 0.149 and 0.324 MeV, respectively. In extrapolation analysis, the QIBP algorithm also effectively improves both models, indicating robust extrapolation capability. In addition, extrapolation based on the synthetic experimental set shows that the QIBP algorithm performs well near the known region and remains effective for most nuclides toward the drip lines. Furthermore, the QIBP algorithm is applied to predict $\alpha$-decay energies of Ra and Es isotopes, and the shell effects manifested in these isotopes are analyzed. This study validates the feasibility of quantum machine learning in nuclear mass research and demonstrates that the proposed algorithm can accurately describe nuclear masses, with potential applications in other areas of nuclear physics.

The kinetic-to-hydrodynamic crossover in the quark-gluon plasma is conventionally diagnosed by scale ratios such as the Knudsen and inverse Reynolds numbers, which are not metrical on the space of distributions. I equip the Denicol–Niemi–Molnär–Rischke (DNMR) 14-moment manifold with the Fisher-Rao metric—the local Hessian of the Kullback-Leibler divergence—and study the resulting Riemannian geometry for conformal Bjorken flow in the relaxation-time approximation. The equilibrium Fisher metric fixes the shear viscosity as $\eta =4P{\tau }_R/5$, identifying near-equilibrium transport as an equilibrium statistical quantity. The full geodesic distance exceeds its linearized approximation by 15–35% at moderate shear, quantifying where Navier-Stokes–type expansions under-resolve the state-space distance. The equilibrium Fisher-Rao Ricci scalar of the five-dimensional shear sector is computed exactly within the truncation to be $R=-5/21$; the negative sign identifies the equilibrium statistical manifold as locally hyperbolic in the Riemannian-geometry sense, which on a statistical model corresponds to diverging geodesic deviation between nearby moment states—a geometric statement about the truncated exponential family, not a prediction for physical relaxation rates. All results are obtained within the DNMR 14-moment truncation for conformal Bjorken flow; the equilibrium relations are closure independent within the truncation, and finite-shear quantities are properties of the Jaynes maximum-entropy completion.

Background: Low-mass neutron-rich isotopes between Fe and Ag are predicted to be synthesized in neutrino-driven winds emitted after the collapse of a massive star. The modeling of this nucleosynthesis scenario, called weak $r$-process or $\alpha$-process, requires large nuclear reaction network calculations. The necessary reaction cross sections are usually taken from the statistical model which uses global optical potentials. Several global $\alpha +$ nucleus optical potential ($\alpha$-OMP) parametrizations exist and deviations between their predicted cross sections exceed even an order of magnitude at astrophysical energies.

Purpose: In the relevant mass range of the weak $r$-process, cross-section calculations performed with the Atomki-V2 potential generally reproduce experimental data within $\pm 50\%$. However, recently the ${}^{88}\mathrm{Sr}$($\alpha ,n){}^{91}\mathrm{Zr}$ cross section was measured and it was found that, unlike other available cross section data, it is lower than the calculations performed with recent OMPs, including the Atomki-V2 calculations, by a factor of 3. Thus, to better understand the source of the discrepancy, the present work aims to determine the ${}^{88}\mathrm{Sr}$ total reaction cross section by measuring ${}^{88}\mathrm{Sr}$($\alpha ,\alpha ){}^{88}\mathrm{Sr}$ elastic scattering angular distributions.

Methods: Between ${\vartheta }_{\mathrm{lab}.}={20}^{\circ }–167.5^{\circ }$ complete elastic $\alpha$ scattering angular distributions were measured at $E_{\mathrm{lab}.}=13.50,16.21,\mathrm{and}19.47\mathrm{MeV}$ energies, with precision better than $7\%$ for each angle.

Results: The total reaction cross section (${\sigma }_{\mathrm{reac}}$) was determined from the experimental data using three independent methods. First, the standard approach of fitting the parameters of the complex $\alpha$-nucleus optical potential was applied. Second, a model-independent phase shift fit was used. Finally, ${\sigma }_{\mathrm{reac}}$ values were also derived using a Bayesian analysis. The excellent agreement of the derived ${\sigma }_{\mathrm{reac}}$ from the three fundamentally different methods shows that the measured angular distributions constrain the total reaction cross sections well.

Conclusions: There is serious tension between the very-well-constrained experimental ${\sigma }_{\mathrm{reac}}$ values from elastic scattering and those obtained from the measured ($\alpha ,n$) data. The present results from elastic scattering are robust, agree well with the prediction of recent $\alpha$-OMPs, and fit into the general systematics of cross sections. Thus, an independent verification of the ${}^{88}\mathrm{Sr}$($\alpha ,n){}^{91}\mathrm{Zr}$ cross section data is clearly needed.

Background: The development of GenIV nuclear reactors will take advantage of fast neutrons. They will necessitate nuclear data of low uncertainties over a wide range of neutron energies, notably above 1 MeV. As far as ${}^{235}\mathrm{U}$ is concerned, current experimental data on average prompt neutron multiplicities $\left({\overline{\nu }}_{\text{prompt}}\right)$ of qualified uncertainties show some discrepancies and do not always cover the full incoming neutron energy range of interest.

Purpose: Measure the average prompt neutron multiplicity in the ${}^{235}\mathrm{U}(n,f)$ reaction as a function of incoming neutron energy between 1 and 700 MeV.

Methods: The double time-of-flight technique was used at the Los Alamos Neutron Science Center to measure incoming and prompt fission neutron energies. The data were measured relative to the very well-known ${}^{252}\mathrm{Cf}\left(\mathrm{sf}\right)$ prompt fission neutron spectrum (PFNS) and ${\overline{\nu }}_{\text{prompt}\text{Cf}}$. The integral over the reconstructed PFNS energy and angle distributions in the ${}^{235}\mathrm{U}(n,f)$ reaction provided ${\overline{\nu }}_{\text{prompt}}$.

Results: ${\overline{\nu }}_{\text{prompt}}$ was obtained between 1 and 700 MeV with uncertainties below 0.5% above neutron incoming energies of 3 MeV. There are discrepancies between the data and the evaluations JEFF 4.0, ENDF/B-VIII.1, and JENDL-5.

Conclusions: The results are the most precise measurements of ${\overline{\nu }}_{\text{prompt}}$ in the ${}^{235}\mathrm{U}$($n,f$) reaction so far and cover well the region of interest for nuclear applications between 1 and 25 MeV. In addition, the data are precise enough to highlight the impact of second-chance fission on the increase rate of ${\overline{\nu }}_{\text{prompt}}$ as a function of the incoming neutron energy.

The observable $v_0\left(p_{\mathrm{T}}\right)$, which quantifies event-by-event fluctuations of the differential transverse-momentum spectrum, has been proposed as a direct and sensitive probe of radial flow in heavy-ion collisions. Recent measurements at the CERN Large Hadron Collider exhibit a clear mass ordering for pions, kaons, and protons at low $p_{\mathrm{T}}$ and a baryon-meson splitting at intermediate $p_{\mathrm{T}}$, resembling the well-known features of elliptic flow $\left(v_2\right)$. In this work, we first derive an analytic expression for $v_0\left(p_{\mathrm{T}}\right)$ within a blast-wave framework that incorporates fluctuations of the freeze-out temperature and radial expansion velocity, and we show that this formulation naturally explains the experimentally observed mass ordering. Furthermore, within a quark coalescence picture, supported by transport simulations using A Multi-Phase Transport model, we demonstrate that the baryon-meson splitting at intermediate $p_{\mathrm{T}}$ emerges dynamically from partonic $v_0\left(p_{\mathrm{T}}\right)$. This study provides deeper insight into the $v_0\left(p_{\mathrm{T}}\right)$ observable and the collective dynamics of the quark-gluon plasma.

The Dalitz decay ${\pi }^0\to e^{+}{e}^{-}\gamma$ has been measured with the highest statistical accuracy obtained so far in the $\gamma p\to {\pi }^{0}p$ reaction with the A2 tagged-photon facility at the Mainz Microtron, MAMI. The value of the slope parameter for the ${\pi }^0$ electromagnetic transition form factor, $a_{\pi }=0.0315\pm 0.{0026}_{\mathrm{stat}}\pm 0.{0010}_{\mathrm{syst}}$, is obtained from the analysis of $2.4\times {10}^6$ ${\pi }^0\to e^{+}{e}^{-}\gamma$ observed decays. Within experimental uncertainties, it is in agreement with existing measurements and theoretical calculations, with its own uncertainty being smaller than previous results based on the analysis of ${\pi }^0\to e^{+}{e}^{-}\gamma$ decays.

Recently, new quark mass dependent three-nucleon $\left(3N\right)$ forces have been identified, whose contributions in nuclear matter exceed expectations of Weinberg power-counting arguments. In this work, we investigate the impact of the most dominant new interaction term, characterized by the coupling $F_2$, in ab initio calculations of medium-mass nuclei. For this, we combine the new $F_2$ interaction with established $3N$ interactions up to next-to-next-to-leading order $\left({\mathrm{N}}^2\mathrm{LO}\right)$ and next-to-next-to-next-to-leading order $\left({\mathrm{N}}^3\mathrm{LO}\right)$ in chiral effective field theory. We explore two fit strategies for the low-energy couplings. The first is based only on few-body observables, while the second also incorporates information from ${}^{16}\mathrm{O}$. Generally, we find that the $F_2$ interaction has a significant impact on energies and radii, however mainly due to changes in the short-range couplings. Overall, we find no significant systematic improvements in the reproduction of medium-mass nuclei when the additional $F_2$ interaction is included.

Microscopic modeling of low-energy spectroscopy in medium-heavy and heavy odd-$A$ nuclei is an outstanding open problem in nuclear physics. We propose a novel spectra-generating collective model for odd-$A$ nuclei constructed by means of the nuclear energy density functional theory and the interacting boson-fermion model. The bosonic Hamiltonian for an even-even nucleus, which is treated as a core, and the strength parameters for the interactions between the core and an odd nucleon are completely determined by using as microscopic inputs the potential energy curves and deformed single-particle spectra obtained from the self-consistent mean-field calculations. In applications to odd-$A$ Eu, Sm, La, and Ba isotopes, we demonstrate the validity of the proposed method in reproducing reasonably the observed low-energy spectra and shape phase transitions in the general cases of the quadrupole collective states, that is, nearly spherical, strongly deformed, and $\gamma$-soft shapes, in the presence of an odd nucleon in a single-$j$ orbit.

Quantum entanglement provides a unique perspective for probing nuclear structure. In this work, we employ quantum entanglement measures, including proton-neutron entanglement entropy, mutual information, and quantum relative entropy, to investigate the evolution of entanglement patterns as we approach neutron-rich nuclei. The study is carried out in the vicinity of the $N=20$ island of inversion region consisting of even-$A$ Ne, Mg, and Si isotopes, and also for isotones corresponding to $N=20$. The state-of-the-art ab initio valence space in-medium similarity renormalization group method is used for this purpose. We highlight the role of proton-neutron entanglement entropy in the formation of the island of inversion region. Mutual information provides insight into the strength of correlations between proton-proton, neutron-neutron, and proton-neutron single-particle states. While these correlations are relatively weak between protons and neutrons in the ground states, they become comparable to like-particle correlations in excited states. The quantum relative entropy is also studied between $0^{+}$ and $2^{+}$ states of the Ne, Mg, and Si isotopes, as well as $N=20$ isotones, using the Kullback-Leibler divergence and Jensen-Shannon divergence. We perform these calculations by expressing the nuclear wave functions in a Slater-determinant basis and analyzing them through complementary partitions, including proton-neutron and mode-resolved factorizations.