We examined the potential impact of decays on the magnitude of fluctuations of net quantum numbers and integrals of balance functions based on a thermal hadron gas model. The calculations are based on a comprehensive list of known hadrons with masses up to $2.5\mathrm{GeV}/c^2$ and include all decays of these hadrons with known branching fractions. The calculations are performed at vanishing baryochemical potential for temperatures between 140 and 200 MeV. We show that the decays feed-down substantially impact the single yield of measurable “stable particles” as well as those of correlated densities of these species. Decays can then potentially have large and nontrivial impacts on measurements of net quantum-number cumulants and balance functions. These observations are particularly important in the context of the search for the QCD critical point at the RHIC Beam Energy Scan as well as efforts to determine chemical susceptibilities near the phase transition at RHIC or LHC energies. Results obtained in this work also shed light on the importance of feed-down in measurements of balance functions in elementary $pp$ and nucleus-nucleus collisions.

To overcome the limitations of existing algorithms for solving self-bound quantum many-body problems—such as those encountered in nuclear and particle physics—that access only a restricted subset of energy levels and provide limited structural information, we introduce and demonstrate a novel quantum-classical approach capable of resolving the complete bound-state spectrum. This method also provides the total angular momentum $J$ associated with each eigenstate. Our approach is based on expressing the Hamiltonian in second-quantized form within a novel input model combined with a scan scheme, enabling broad applicability to configuration-interaction calculations across diverse fields. We apply this hybrid method to compute, for the first time, the bound-state spectrum together with corresponding $J$ values of ${}^{20}\mathrm{O}$ using a realistic strong-interaction Hamiltonian. Our approach applies to hadron spectra and $J$ values solved in the relativistic basis light-front quantization approach.

Short-range correlations (SRCs) provide the link between low- and high-energy nuclear physics and can be quantified by two-nucleon densities. We present calculations of the two-nucleon densities using free-space similarity renormalization group (SRG)-evolved operators and in-medium SRG (IMSRG) ground states with a softened chiral interaction. Our calculations benchmark well against no-core shell model results with unevolved operators and Hamiltonians in ${}^4\mathrm{He}$. We explicitly include the induced three-body (3b) density operators for the first time which, together with the 3b Hamiltonians, provide the full 3b effects. We show pronounced 3b effects in the ${}^{16}\mathrm{O}$ two-nucleon densities. Combined with valence-space IMSRG method, we extend the calculation to the oxygen isotopic chain. This approach enables a consistent ab initio description of low-energy properties and SRCs within one framework and offers predictions for the upcoming SRC measurements in unstable nuclei.

Background: Quasifission is a nonequilibrium phenomenon that strongly suppresses the formation of heavy nuclei in heavy-ion fusion reactions. This process shows a strong entrance channel dependence. Understanding quasifission is crucial for exploring potential avenues to synthesize new superheavy elements and their isotopes.

Purpose: To study the interplay of fusion-fission and quasifission with increasing $Z_p{Z}_t$ for the reactions using ${}^{197}\mathrm{Au}$ as the target. To explore the variation of average sticking time in these reactions with a constant target deformation.

Methods: The mass-angle distributions of fission and fission-like fragments were measured for seven reactions using ${}^{197}\mathrm{Au}$ as the target at energies near the Coulomb barrier. Negligible sequential fission is expected in these reactions; thus, the measured binary products represent the total quasifission yield. Pulsed beams of ${}^{32,36}\mathrm{S}$, ${}^{48}\mathrm{Ca}$, ${}^{50}\mathrm{Ti}$, ${}^{54}\mathrm{Cr}$, ${}^{58}\mathrm{Fe}$, and ${}^{64}\mathrm{Ni}$ were used in the study. A systematic analysis of mass ratio distributions and mass widths has been carried out. The experimental mass-angle distribution is simulated following a phenomenological approach. The average sticking time for the fast quasifission is extracted from the simulations.

Results: Dominant mass-symmetric fission fragments with a slight mass-angle correlation are observed in the most mass-asymmetric (${}^{32,36}\mathrm{S}+{}^{197}\mathrm{Au}$) reactions. In contrast, a $\mathsf{U}$-shaped mass ratio distribution has been observed in the most symmetric (${}^{64}\mathrm{Ni}+{}^{197}\mathrm{Au}$) reaction. A sharp decrease in fusion probability is inferred with increasing $Z_p{Z}_t$. The width of the mass ratio distribution is found to increase exponentially with the increase in mean fissility for a fixed beam energy relative to the barrier. The average sticking time of fast quasifission is found to vary from approximately 14 to 15 zeptoseconds to approximately 4 to 5 zeptoseconds for the systems under study.

Conclusion: The observed transition from a dominant symmetric mass split to an asymmetric mass split with mass-angle correlations indicates the increasing probability of fast quasifission and fusion suppression with increasing $Z_p{Z}_t$. The observation is correlated with the sharp fall in the extracted average sticking time with increasing $Z_p{Z}_t$ from 1264 to 2212.

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.