The ability of the radial basis function (RBF) approach to extrapolate the nuclear masses and $\alpha$-decay energies is systematically investigated using eight nuclear mass models. The effective extrapolation distance of the RBF approach is found to be proportional to the root-mean-square deviation between model predictions and experimental data for known nuclei. Extended extrapolation distances may indicate missing physical mechanisms in the original nuclear mass models. For most models, the RBF approach demonstrates greater improvement in prediction accuracy for neutron-rich nuclei compared to proton-rich systems. In the superheavy region, combining the RBF approach with existing mass models through direct learning of known masses does not significantly enhance $\alpha$-decay energy prediction accuracy for nuclei with $Z>110$. However, applying the RBF approach to directly learn known $\alpha$-decay energies rather than nuclear masses proves more effective for enhancing prediction accuracy in this region. The $\alpha$-decay energies of 125 superheavy nuclei with $Z=111–120$ are predicted.

It is the aim of this study to quantify the role of in-medium $3\leftrightarrow 3$ collisions for systems of fermions which initially are out-of equilibrium. The formulation of the three-body dynamics is based on the equations of motion method for identical fermions—also denoted as quantum correlation dynamics—and presented in detail. The on-shell two-body collision integral is briefly reviewed and the on-shell three-two-body collision integral is derived on the basis of the same two-body interaction in leading order. The resulting equations obey particle number as well as energy-momentum conservation. For a quantification of the relative impact of three-body interactions a model study is employed for a homogeneous system in space in a finite box with periodic boundary conditions. Here, spin-isospin symmetric nuclear matter systems are addressed with momentum distributions that are given by shifted Fermi spheres (without overlap) as encountered in the initial phase of nucleus-nucleus collisions after contact. The results for the relaxation times—employing an effective two-body interaction—are compared to Boltzmann-Uehling-Uhlenbeck (BUU) transport calculations in the continuum limit. It is found that the additional three-body interactions reduce the relaxation times up to a factor of 3 at 130 MeV/nucleon. Furthermore, it is shown in BUU transport calculations that an enhanced stopping by $3\leftrightarrow 3$ collisions shows up in the angular distribution of energetic nucleons ($>60\mathrm{MeV}$), e.g., in central ${}_{45}{}^{97}\mathrm{Rh}$ collisions at 40 MeV/nucleon that lead to the formation of a compound nucleus. The angular distribution of the energetic nucleons changes from a slightly forward peaked angular distribution to a slightly sidewards peaked angular distribution which might be controlled experimentally.

It was shown that light nuclei such as ${}^4\mathrm{He}, {}^8\mathrm{Be}$, and ${}^{12}\mathrm{C}$ can be well described by RMF models, which enables a unified description for nuclei with baryon numbers $A\gtrsim 4$. In this work, I propose a hybrid treatment for investigating the clustering phenomenon in nuclear medium, where clusters ranging from light nuclei (e.g., ${}^3\mathrm{H}, {}^3\mathrm{He}$, and ${}^4\mathrm{He}$) to heavy ones (e.g., ${}^{12}\mathrm{C}, {}^{16}\mathrm{O}, {}^{40}\mathrm{Ca}, {}^{48}\mathrm{Ca}$, and ${}^{208}\mathrm{Pb}$) can be treated in a unified manner. In particular, assuming a spherical Wigner-Seitz cell, the clusters are fixed by solving the Dirac equations imposing the Dirichlet-Neumann boundary condition, while the nuclear medium are treated with Thomas-Fermi approximation and take constant densities. In the presence of nuclear medium, the clusters eventually become unbound as density increases, while the root-mean-square charge radii increase. For clusters with different proton and neutron numbers $N_p\ne N_n$, their binding energies vary with the proton fraction of nuclear medium, which are less significant for clusters with $N_p=N_n$. The uncertainties of density functionals on the clustering phenomenon are investigated as well, adopting 8 different functionals. Based on the obtained results, an analytical formula describing the binding energies of in-medium clusters is then obtained. The results presented in this work should be useful to understand the clustering phenomenon in both heavy-ion collisions and neutron stars.

We investigated the evolution of shell structure at $N=32$ and 34 in neutron-rich nuclei beyond the stability line using realistic nuclear forces, employing the state-of-the-art valence-space in-medium similarity renormalization group method. The shell gaps are discussed from the excitation energies of the first $2^{+}$ states and the evolution of effective single-particle energies. We addressed different components of the nuclear interaction—central, spin-orbit, and tensor—and their roles in the development of shell gaps far from stability. The calculated results align well with the available experimental data and suggest a strengthening of the $N=34$ subshell gap and a weakening of the $N=32$ subshell gap below Ca. Additionally, the low-energy structures of the exotic $N=32$ isotones below Ca revealed that their ground states exhibit large deformation and coexist with a weakly deformed band at low excitation energy. The present work demonstrates essential components of the nuclear force in shaping magic numbers far from stability and provides deeper insights into the structure of exotic nuclei from the underlying nuclear forces.

Isotopes in the region of the nuclear chart below ${}^{68}\mathrm{Ni}$ have been the subject of intense experimental and theoretical effort due to the potential onset of a new “island of inversion” when crossing the harmonic oscillator subshell closure at $N=40$. We have measured the masses of ${}^{64-68}\mathrm{Mn}$ using TITAN's multiple-reflection time-of-flight mass spectrometer, resulting in the first precision mass measurements of ${}^{67}\mathrm{Mn}$ and ${}^{68}\mathrm{Mn}$. These results are compared to ab initio calculations and modern shell model calculations and show an increase in collectivity approaching $N=40$.

This study optimizes resonance parameters responsible for strangeness production in the SMASH (Simulating Many Accelerated Strongly-interacting Hadrons) transport model using a genetic algorithm. By fitting resonance parameters to experimental data on exclusive strangeness cross sections at low energies, we significantly improve the model's accuracy, notably in pion-proton interactions. Our approach explores how machine-learning tools can be used for precise resonance tuning in transport approaches.

We have measured the $0_{gs}^{+}\to 2_1^{+}$ transition in the neutron-rich $N=28$ isotope ${}^{42}\mathrm{Si}$ using the probes of intermediate-energy Coulomb excitation and inelastic proton scattering in inverse kinematics at the Facility for Rare Isotope Beams with beam particle rates of $\approx 5$ particles/s. The results of these two measurements allowed us to determine $M_n/M_p$, the ratio of the neutron and proton transition matrix elements for the $0_{\mathrm{g}}.\mathrm{s}{.}^{+}\to 2_1^{+}$ transition. In addition, we have measured the $0_{\mathrm{g}}.\mathrm{s}{.}^{+}\to 2_1^{+}$ transition in the isotone ${}^{44}\mathrm{S}$ using inverse kinematics inelastic proton scattering. By comparing the ${}^{44}\mathrm{S}$ proton-scattering result with a recent intermediate-energy Coulomb excitation result on the same transition, we were able to determine $M_n/M_p$ for the $0_{\mathrm{g}}.\mathrm{s}{.}^{+}\to 2_1^{+}$ transition in this nucleus as well. This work strengthens the evidence that ${}^{42}\mathrm{Si}$ has a stable quadrupole deformation in its ground state and that ${}^{44}\mathrm{S}$ does not. Both conclusions are further supported by shell-model calculations carried out with the FSU interaction

The present study investigates the role of incomplete fusion (ICF) in heavy-ion reactions alongside complete fusion (CF) by measuring the recoil ranges of reaction residues. To distinguish between CF and ICF contributions, the linear momentum transfer from the projectile to the target nucleus was analyzed. Forward recoil range distributions (FRRDs) of radioactive residues formed in the ${}^{16}\mathrm{O}+{}^{174}\mathrm{Yb}$ system were measured at beam energies of 84.55 and 94.92 MeV using the recoil-catcher activation technique. The analysis of these distributions revealed signatures of both CF and ICF processes. Larger recoil ranges were associated with complete linear momentum transfer during CF, while reduced recoil ranges indicated partial momentum transfer caused by the incomplete fusion of the projectile. The findings suggests that the ICF probabilities generally increases with the target mass. However, an exception is observed for the ${}^{16}\mathrm{O}+{}^{174}\mathrm{Yb}$ system, where the observed lower $F_{\mathrm{ICF}}$ value is attributed to the smaller deformation parameter (${\beta }_2$) of ${}^{174}\mathrm{Yb}$ compared to ${}^{169}\mathrm{Tm}$. This indicates that nuclear deformation plays a crucial role in governing ICF reaction dynamics. Further, the measured total CF cross sections were compared with theoretical values of ccfull code and were found to be in good agreement. This system was also studied to investigate the presence of fusion hindrance phenomena at deep sub-barrier energies. It was observed that fusion is not hindered up to energy $\approx 11\%$ below the Coulomb barrier. Moreover, this study explores the production of medically relevant radioisotopes, including ${}^{186}\mathrm{Pt}$, using heavy-ion induced reactions. The findings highlight their potential theranostic applications, contributing to advances in nuclear medicine.

Background: The SMASH-vHLLE-hybrid model integrates the SMASH transport code for the hadronic phase and the vHLLE hydrodynamic model for the quark-gluon plasma (QGP) phase in heavy-ion collisions. Bayesian analysis offers a robust statistical method to constrain model parameters of a hybrid approach and evaluate uncertainties by comparing predictions with experimental data. Traditional modeling often relies on parametric assumptions for initial conditions, which may limit the ability to constrain the parameter space due to overfitting.

Purpose: This study aims to apply statistical learning, specifically Bayesian inference, to the $(3+1)\text{−}\mathrm{dimensional}$ [(3+1)D] SMASH-vHLLE-hybrid model using initial conditions generated by the SMASH transport code itself, with the objective of constraining model parameters and gaining deeper insight on the temperature and baryochemical potential dependence of both the shear and the bulk viscosity.

Method: This study is performed in the hybrid approach SMASH-vHLLE, composed of the hadronic transport approach SMASH and the $(3+1)\mathrm{D}$ viscous hydrodynamic code vHLLE. A Bayesian framework is employed, utilizing Markov-chain Monte Carlo sampling to explore the parameter space. The analysis compares model predictions against experimental observables in the range of $\sqrt{s_{NN}}=7.7\text{–}200$ GeV, including particle yields, momentum, and flow coefficients both at midrapidity as well as in forward and backward direction.

Results: We find that the SMASH-vHLLE-hybrid framework, using hadronic initial conditions for $\mathrm{Au}+\mathrm{Au}$ collisions at different beam energies, can reproduce a variety of experimental observables at midrapidity and forward/backward rapidities. Notably, the preferred posterior distribution suggests a near-vanishing specific shear viscosity in the high-temperature QGP phase, combined with moderate-to-large bulk viscosity around the phase transition region, although the constraints on baryochemical potential dependence are weak.

Conclusions: Our findings reveal that a hadronic initial condition constrains the evolution more strictly at intermediate energies, making parameters such as the hydrodynamic onset time highly sensitive. Intriguingly, the extracted shear viscosity differs substantially from previous Bayesian analyses, motivating further systematic studies with higher-statistics data sets and refined modeling assumptions.

We present a high-precision mass measurement of the proton-rich nucleus ${}^{23}\mathrm{Si}$, performed with the LEBIT Penning trap at the Facility for Rare Isotope Beams (FRIB) utilizing the time-of-flight ion cyclotron resonance (TOF-ICR) technique. We determined a mass excess of 23362.9(5.8) keV, which agrees with a recent storage-ring measurement from the experimental Cooler-Storage Ring (CSRe) in Lanzhou but has a factor of 20 improved precision. ${}^{23}\mathrm{Si}$ is hence the nucleus with the most precisely known mass among all nuclei with an isospin projection of $T_z=-5/2$. We performed shell-model calculations with the USDC and USDCm Hamiltonians to study binding energy differences and Thomas-Ehrmann shifts in mirror systems with an isospin up to $T=5/2$. Our experimental result and other recently reported masses of neutron-deficient sd-shell nuclei agree well with the theoretical predictions, demonstrating that isospin symmetry breaking in sd-shell nuclei—even at high isospin values—is well described by modern shell-model calculations.

Since the nuclear interaction is, to first order, isospin independent, simple relationships can be derived for $E2$ strengths across isobaric analog states within an isobaric triplet. At the same time, there is a well-known relationship between the $2^{+}$ excitation energy and the $B(E2;2^{+}\to 0^{+}$) transition strength in deformed even-even nuclei. Here, we highlight a tension between these two trends in the $A=78$ isobaric triplet. Recent level-energy determinations indicate that the proton-rich member of the triplet, ${}^{78}\mathrm{Zr}$, is strongly deformed while recent lifetime measurements in ${}^{78}\mathrm{Sr}$ and ${}^{78}\mathrm{Y}$, as extrapolated into ${}^{78}\mathrm{Zr}$, would imply that ${}^{78}\mathrm{Zr}$ is weakly deformed. Here, we explore the implications of this apparent contradiction and explore potential solutions.

Background: Multinucleon transfer (MNT) reactions are now considered as a possible tool to produce new isotopes of heavy and superheavy elements.

Purpose: Experimental study of MNT fragments formed in the ${}^{209}\mathrm{Bi}+{}^{238}\mathrm{U}$ reaction at ${}^{209}\mathrm{Bi}$ beam energy of 1.85 GeV and comparison with the previous measurements of the ${}^{136}\mathrm{Xe}+{}^{238}\mathrm{U}$ system [E. M. Kozulin et al., Phys. Rev. C 109, 034616 (2024)].

Methods: Primary and secondary mass and energy distributions of projectile-like fragments (PLF) formed in the ${}^{209}\mathrm{Bi}+{}^{238}\mathrm{U}$ reaction have been experimentally investigated independently and in coincidence with survived heavy target-like fragments (TLFs) using the CORSET setup. Since the heavy fragments formed in the reaction are highly excited, the masses, energies, and angles of both fragments as products of the sequential fission of heavy MNT fragments have been measured.

Results: The cross sections for PLFs at $27.2^{\circ }\le {\theta }_{\mathrm{lab}}\le 32.8^{\circ }$ along with survived TLFs and TLFs undergoing fission have been obtained. The mass loss during the deexcitation process of excited PLFs has been found using the measured primary and secondary masses. The excitation energies of light and heavy MNT fragments have been estimated from the mass loss and total kinetic energies. An overall good agreement with theoretical calculations increases the reliability of the analysis.

Conclusions: The transfer of about 46 nucleons from the projectile to the target nucleus has been found. The cross section of the heaviest observed fragment with the mass of 284 u is about hundred microbarns. The heaviest survived fragments with mass 258 u and cross section of about 10 microbarns correspond to the formation of heavy actinide nuclei up to mendelevium.

A stochastic approach based on four- and five-dimensional (5D) Langevin equations has been used to simulate the fission dynamics of the excited compound nucleus ${}^{233}\mathrm{Th}$ at low excitation energies. In the dynamical calculations, not only has the two-center shell model parametrization of nuclear shape been taken into account but also the projection of total spin of the compound nucleus to the symmetry axis, $K$. In the 5D dynamical model was used four collective shape coordinates $\left\{z_0/R_0,{\delta }_1,{\delta }_2,\eta \right\}$ plus the projection of total spin of the compound nucleus to the symmetry axis, $K$, and in the four-dimensional (4D) dynamical model used three collective shape coordinates $\left\{z_0/R_0,{\delta }_1={\delta }_2=\delta ,\eta \right\}$ plus the projection of total spin of the compound nucleus to the symmetry axis. The potential energy at low excitation energy was calculated by the finite range liquid drop model when considering shell and pairing effects. The Werner-Wheeler approximation was used to calculate the inertia tensor and the wall-and-window model with a reduction coefficient, $k_s$, was applied to calculate the fraction tensor. The fission probability, the mean total kinetic energy of fission fragments, the fission fragment mass yield, and the fission time distribution have been calculated for the excited compound nucleus ${}^{233}\mathrm{Th}$. Furthermore, the fission fragment mass yields have been calculated for ${}^{222}\mathrm{Th}$, where the symmetric fission component is dominant as well as for ${}^{226}\mathrm{Th}$, where the asymmetric component rapidly grows. In the calculations, the reduction coefficient was considered as a free parameter and its magnitude inferred for the excited compound nucleus ${}^{233}\mathrm{Th}$ by fitting measured data on the fission probability. It was shown that the results of calculations for the fission probability is in good agreement with the experimental data by using the magnitude of the reduction coefficient equal to $k_s=0.29$ for the excited compound nucleus ${}^{233}\mathrm{Th}$. Furthermore, in the 5D Langevin model the influence of different parameters, i.e., the reduction coefficient of nuclear dissipation, $k_s$, the deformation parameters, ${\delta }_i$, the dissipation coefficient of K, ${\gamma }_K$, the shell damping parameter, $E_d$, and the fission time were investigated on the simulation of fission dynamic of the excited compound nucleus ${}^{233}\mathrm{Th}$. According to the comparison of the results of the 4D and 5D Langevin models, it was shown that the 5D model is able to reproduce the experimental results more appropriately than the 4D model.

Measurements of global spin alignment of vector mesons in relativistic heavy-ion collisions can provide unique insights into spin-orbit interactions and vector meson dynamics in the quark-gluon plasma produced in those collisions. The global spin alignment is measured by the 00th coefficient of the spin density matrix, ${\rho }_{00}$, via the polar angle (${\theta }^{*}$) of the decay-kaon momentum in the parent rest frame with respect to the direction of the orbital angular momentum of the collision. Such measurements are affected by the angular and momentum resolutions of the reconstructed tracks in the experiment. Such effects are nontrivial because of kinematic complications caused by the boost to the parent rest frame, and could be important given that the global spin alignment signal is weak. In this paper, we investigate the effects of experimental tracking resolutions on measurements of the $\varphi$(1020) meson ${\rho }_{00}$. We study these effects for two methods of ${\rho }_{00}$ measurements, the conventional method analyzing the $\varphi \text{−}\mathrm{meson}$ yield versus ${cos}^2{\theta }^{*}$ and the invariant mass ($m_{\mathrm{inv}}$) method utilizing $\langle {cos}^2{\theta }^{*}\rangle$ versus $m_{\mathrm{inv}}$. Using typical resolution values from experiments, we find that the effect of track resolution on ${\rho }_{00}$ is small, well within typical measurement uncertainties.

Based on the empirical coupled-channel (ECC) model for calculating capture cross section and the statistical model for calculating survival probability, we adopt the dinuclear system (DNS) model for a systematic investigation of the evaporation-residue (ER) cross sections of the reactions leading to superheavy nuclei (SHN). The theoretical results can systematically reproduce the experimental data of the hot-fusion reactions with ${}^{48}\mathrm{Ca}$ as the projectile. Simultaneously, the ER cross sections of superheavy elements (SHEs) 112–120 from ${}^{50}\mathrm{Ti}$-induced fusion reactions are systematically investigated. The calculated ER cross sections for the reactions ${}^{50}\mathrm{Ti} +{}^{246,247,248,249}\mathrm{Bk}$ and ${}^{249,250,251,252}\mathrm{Cf}$ to produce the SHN with $Z=$ 119 and 120 are given. It is found that the projectile-target combinations ${}^{50}\mathrm{Ti}+{}^{249}\mathrm{Bk}$ and ${}^{50}\mathrm{Ti}+{}^{251}\mathrm{Cf}$ are considered as the most promising reactions with ${}^{50}\mathrm{Ti}$ as projectile for the syntheses of the next two SHEs beyond Og. The maximal ER cross section for ${}^{50}\mathrm{Ti}+{}^{249}\mathrm{Bk}$ is 79.6 fb at the incident energy $E_{\mathrm{c}.\mathrm{m}.}=229.5$ MeV. For ${}^{50}\mathrm{Ti}+{}^{251}\mathrm{Cf}$, the maximal ER cross sections are about 17.5 fb at the incident energies around $E_{\mathrm{c}.\mathrm{m}.}=235$ MeV.

We study the possibility of a low-energy nuclear fusion reaction assisted by a low-energy resonance. We use a simple potential model and replace repulsive Coulomb barrier with the step potential barrier. This is convenient since it allows us to perform analytic calculations and have better control on approximations. The fusion process involves a proton and another nucleus. We first consider a process in which this transition takes place by emission of a photon at first order in perturbation theory. The cross section for this process is highly suppressed due to the presence of repulsive barrier. We next consider another process, which involves emission of two photons. This process gets dominant contribution at second order in perturbation theory. We find a fairly large cross section provided the initial energy is taken to be significantly larger than the resonant energy. The exponential suppression factors cancel out in this calculation leading to a cross section much larger than the first-order process. As an example, for a particular set of potential parameters and initial state energy chosen in this paper, we find an enhancement of 29 orders of magnitude. Assuming a fixed initial energy, the experimental signature for this process is two-photon emission within a narrow range of energies. One of the photon would be emitted at low energy of order of the initial state energy and the second would correspond to nuclear energy.

The $\mathrm{\Lambda }N$ invariant mass spectra for the reactions $K^{-}d\to {\pi }^{-}\mathrm{\Lambda }p$ and $K^{-}d\to {\pi }^0\mathrm{\Lambda }n$ are calculated for experimental study of isospin symmetry breaking in the $\mathrm{\Lambda }N$ scattering at low energies, the difference in the scattering lengths and effective ranges of $\mathrm{\Lambda }p$ and $\mathrm{\Lambda }n$ systems. The calculations are performed for in-flight kaons with a momentum of 1000 MeV/$c$ with employing partial wave analysis up to the $p$ wave for meson-baryon amplitudes and the spin-flip term for baryon-baryon amplitudes. Kinematic selection is utilized to suppress the background processes by selecting forward-emitting pions and higher momentum nucleons. It is worth noting that isospin symmetry breaking in the $\mathrm{\Lambda }N$ system can be extracted from the difference of the $\mathrm{\Lambda }N$ invariant mass spectra between the $K^{-}d\to {\pi }^{-}\mathrm{\Lambda }p$ and $K^{-}d\to {\pi }^0\mathrm{\Lambda }n$ reactions.

Background: The rate of energy production in the hot-CNO cycle and breakout to the rapid-proton capture process in Type I X-ray bursts is strongly related to the ${}^{14}\mathrm{O}(\alpha ,p){}^{17}\mathrm{F}$ reaction rate.

Purpose: The properties of states in ${}^{18}\mathrm{Ne}$ near $E_x=6.1–6.3$ MeV are important for understanding the ${}^{14}\mathrm{O}(\alpha ,p){}^{17}\mathrm{F}$ reaction rate.

Methods: In order to study ${}^{18}\mathrm{Ne}$ resonances around this energy region, the RESOLUT radioactive-ion beam facility at Florida State University was used to perform ${}^{17}\mathrm{F}(p,p){}^{17}\mathrm{F}$ elastic scattering on a polypropylene target under inverse kinematics. Scattered protons were detected in a silicon-strip detector array while recoiling ${}^{17}\mathrm{F}$ ions were detected in coincidence in a gas ionization detector. An $R$-matrix analysis of measured cross sections was conducted along with a reanalysis of data from previous ${}^{17}\mathrm{F}+p$ measurements.

Results: All the data analyzed are well described by a consistent set of parameters with a $1^{-}$ assignment for a state at 6.14(1) MeV. A second comparable solution is also found with a $3^{-}$ assignment for the 6.14(1) MeV state.

Conclusions: There is no conclusive evidence supporting one of the two solutions over the other. The rates of the ${}^{14}\mathrm{O}(\alpha ,\mathrm{p}){}^{17}\mathrm{F}$ reaction that are determined from the two solutions differ by up to an order of magnitude.