Experimental and theoretical studies of photonuclear reactions on a natural mixture of erbium isotopes were performed. The cross sections per equivalent photon and the yields of photonuclear reactions were measured using bremsstrahlung γ radiation with an end-point energy of 55 MeV. The cross sections for photoproton reactions on a natural mixture of erbium isotopes were obtained for the first time. The experimental results are compared with calculations based on the combined model of photonucleon reactions and simulations using the TALYS 2.0 code with different photon strength functions. Theoretical calculations within the combined model of photonucleon reactions included contributions from various mechanisms of $\gamma$-ray interaction with the nucleus: the giant dipole resonance accounting for its isospin splitting and overtone, the isovector quadrupole resonance, and the quasideuteron mechanism of photoabsorption. Additionally, the radiochemical yields of reactions on a natural mixture of erbium isotopes, leading to the formation of the target medical isotope ${}^{166}\mathrm{Ho}$ and by-product nuclides, were determined.

Anisotropic flows in heavy-ion collisions provide a basic experimental observable to understand nuclear collision dynamics and to constrain the dense nuclear matter equation of state (EOS). Within the framework of the lattice Boltzmann-Uehling-Uhlenbeck transport model, we present a systematic study of proton anisotropic flow observables measured by the HADES Collaboration, by utilizing the recently developed nuclear effective interaction based on the density-, momentum-, and isospin-dependent N5LO Skyrme pseudopotential. In particular, we investigate the impacts of the momentum dependence of nucleon mean-field potentials, the stiffness of the symmetric nuclear matter (SNM) EOS, the high-density behaviors of the symmetry energy, and the in-medium modification of nucleon-nucleon elastic cross sections on proton directed ($v_1$), elliptic ($v_2$), triangular ($v_3$), and quadrangular ($v_4$) flows in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=2.4\text{GeV}$. Our results show that the proton anisotropic flows are strongly sensitive to the momentum dependence of the nucleon mean-field potential as well as the incompressibility coefficient $K_0$ of SNM. In addition, the transverse momentum dependence of the proton $v_2$ exhibits a modest sensitivity to the higher-order skewness coefficient $J_0$ and kurtosis coefficient $I_0$ of SNM as well as the momentum dependence of the symmetry potential, while the transverse momentum dependence of the proton $v_1$ is shown to modestly depend on the in-medium modification of nucleon-nucleon elastic cross sections. Moreover, the high-density symmetry energy seems to have limited effects on the proton anisotropic flows. These findings highlight the necessity of considering the momentum dependence of nucleon mean-field potentials including the symmetry potential, the higher-order characteristic parameters of the SNM EOS beyond $K_0$, and the in-medium modification of nucleon-nucleon elastic cross sections, in future Bayesian transport model analyses on proton anisotropic flows in heavy-ion collisions at HADES energies, for the purpose of extracting information on the nuclear matter EOS as well as the associated underlying nuclear effective interactions.

I present a fully microscopic description of the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion reaction at stellar energies. Utilizing the multichannel resonating group method (RGM), my model explicitly includes ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ and $\alpha {+}^{20}\mathrm{Ne}$ reaction channels (with excited states). This approach provides a consistent, simultaneous description of fusion, elastic scattering, and ${}^{24}\mathrm{Mg}$ spectroscopy. Results for ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ elastic scattering show excellent agreement with experimental data, significantly improving the single-channel approximations. Spectroscopic analysis reveals that ${}^{24}\mathrm{Mg}$ states and resonances are highly mixed configurations, contradicting the concept of pure “molecular states.” The calculated fusion $S$ factor is consistent with available experimental data and predicts both narrow and broad resonances near the Coulomb barrier. Main resonance widths originate primarily from the $\alpha +{}^{20}\mathrm{Ne}$ exit channels. The $S$ factor exhibits a decrease at low energies, providing a microscopic support for the hypothesis of fusion hindrance. This work is a first step toward a reliable theoretical extrapolation of the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reaction to deep stellar burning temperatures. Future works should include the neutron and proton channels to provide a complete description of the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ fusion.

The present work investigates the causal parameter space of the Mueller-Israel-Stewart second-order theory for heat-conducting fluids in the Eckart frame for one-dimensional fluid flow in systems with finite baryon density. It is shown that this parameter space is highly constrained and particularly sensitive to the equation of state and second-order transport coefficients. Through numerical analysis of the characteristic equations, the present analysis identifies regions of strong hyperbolicity, weak hyperbolicity, and nonhyperbolicity, mapping the boundaries of causality violation as functions of the heat flux to energy density ratio $q/\varepsilon$ and relaxation parameters. The present work also explores the causality conditions using a realistic lattice QCD based equation of state. Using the Navier-Stokes approximation, an estimate is made of the heat flow magnitude to assess causality criteria for one-dimensional heat conduction in heavy-ion collisions. The present calculations reveal unrealistically large heat flux values ($\left|\mathbf{q}\right|/\varepsilon \approx 330–811$) for typical conditions at the BNL Relativistic Heavy Ion Collider when using thermal conductivity estimates from kinetic theory models, suggesting either significant overestimation of transport coefficients or breakdown of the fluid approximation in these extreme conditions. The pressure gradient corrections reduce the heat flow by approximately 15% but do not resolve the causality concerns.

We study how the inclusion of energy dependence as dictated by quantum chromodynamic (QCD) small-$x$ evolution equations affects key observables in ultrarelativistic heavy-ion collisions. Specifically, we incorporate JIMWLK evolution into the IP-Glasma framework, which serves as the initial condition for a simulation pipeline that includes viscous relativistic hydrodynamics and a hadronic afterburner. This approach enables a consistent modeling of highly energetic nuclei across varying Bjorken-$x$ values, which are relevant for different collision energies and rapidity regions. In comparison to the standard IP-Glasma setup without small-$x$ evolution, we observe pronounced changes in particle multiplicities and spectral distributions, especially in smaller systems and at the highest available energies. We further explore effects on anisotropic flow observables and correlations between mean transverse momentum and elliptic flow. Our findings underscore the critical role of nonlinear QCD evolution in accurately modeling the early stages of heavy-ion collisions, as well as its implications for extracting transport properties of the quark-gluon plasma.

We introduce a dilated coordinate method to address computational challenges in nuclear lattice effective field theory for weakly bound few-body systems. The approach employs adaptive mesh refinement via analytic coordinate transformations, dynamically adjusting spatial resolution to resolve short-range nuclear interactions with fine grids while efficiently capturing long-range wave function tails with coarse grids. Numerical demonstrations for two- and three-body systems confirm accelerated convergence towards infinite-volume limit compared to uniform lattices, particularly beneficial for accessing highly excited states and shallow bound states near the continuum threshold. This method establishes a foundation for ab initio studies of exotic nuclear systems near the dripline and light hypernuclei, with direct extensions to scattering and reaction processes.

Discretizing the Dirac equation on a uniform grid with the central difference formula often generates spurious states. We propose a staggered-grid scheme in the framework of the finite-difference method that suppresses these spurious states without introducing Wilson terms or $\mathit{ad}$ hoc filtering. In this approach, the large and small components of the Dirac equation are placed on interlaced nodes, and the first-order derivatives are evaluated between staggered points, yielding a Hamiltonian that breaks the unitary transformation between $H_{\kappa }$ and $H_{-\kappa }$. Benchmarks with the nuclear Woods–Saxon potentials demonstrate one-to-one agreement with the eigenvalues obtained from the shooting method and the asymmetric finite-difference method, rapid convergence for weakly bound states, and reduced box-size sensitivity. The method retains the simplicity of central differences and standard matrix diagonalization, while naturally extending to higher-order and multidimension systems. It provides a compact and efficient tool for relativistic bound-state and scattering calculations.

In this work, the particle number projection at finite temperature is incorporated into self-consistent Skyrme density functional calculations. In particular, the energies of compound nuclei as a function of deformations are calculated rigorously based on projected densities. Results show that the even-odd staggering effect in the partition function gradually diminishes as the system approaches the critical temperature. The obtained fission barriers are similar to that without projection at finite temperature, although projected energies are different. The nuclear level density at the ground state and the barrier are also studied using the projection method and the discrete Gaussian method.

We analyze the elastic $\alpha -{}^{12}\mathrm{C}$ scattering including the contribution of resonance states below the $p-{}^{15}\mathrm{N}$ breakup threshold energy. We use the cluster effective field theory in which scattering amplitude is expanded in terms of the effective range expansion parameters for the angular momentum states from $l=0$ to $l=6$. The amplitude contains 37 parameters, which are determined by fitting to 11 392 differential cross section data points of the elastic $\alpha -{}^{12}\mathrm{C}$ scattering. To optimize the fitting process, we implement the differential evolution (DE) algorithm, which performs a global search over the high-dimensional parameter space and consistently converges to the same minimum ${\chi }^2$ value across independent runs, suggesting proximity to the global minimum within the explored domain. In parallel, the Markov chain Monte Carlo (MCMC) method is used to crosscheck the DE results and to estimate the parameter uncertainties. The best fit yields ${\chi }^2/N\simeq 6.2$ for the elastic scattering data. Using the determined 37 parameters, we calculate the differential cross sections and the phase shifts of the elastic $\alpha -{}^{12}\mathrm{C}$ scattering and compare the results with experimental data and those of an $R$-matrix analysis. Our result of the cross section agrees with the experimental data as accurately as an $R$-matrix analysis. The results demonstrate that the cluster effective field theory, combined with global optimization and uncertainty quantification based on DE-MCMC methods, provides a reliable and systematic framework for applications to low energy phenomena relevant to stellar evolution and nucleosynthesis.

In this work, I present a phenomenological search for light neutral spin-1 vector mediators in elastic electron-proton ($ep$) scattering using a two-photon-exchange (TPE)-consistent framework. A vector boson that couples to electrons and protons modifies the $\varepsilon$-independent part of the unpolarized reduced elastic cross section ${\sigma }_R(\varepsilon ,Q^2)$ through interference with the photon, producing a characteristic shift in the Rosenbluth intercept. Using the full set of available Rosenbluth separations and a TPE-corrected baseline constructed from the Borisyuk-Kobushkin parametrization, I extract the intercept deviation across all measured $Q^2$ values spanning $0.0155\le Q^2\le 5.5{\mathrm{GeV}}^2$ and perform a profile-likelihood analysis to determine mass-dependent limits on the effective vector coupling. The data show no evidence for a vector contribution over the vector mass $m_V$ range of 0.04–10 GeV, and the resulting one-sided 95% C.L. upper bounds reach the few $\times {10}^{-4}-{10}^{-3}$ level at low mediator masses, weakening to the ${10}^{-3}-{10}^{-2}$ level at larger $m_V$ as expected from propagator suppression. These results provide strict, model-independent constraints on light vector interactions in elastic $ep$ scattering once TPE effects are consistently included.

Rapidity asymmetry of jet-hadron correlation has been proposed as a robust signal of dijet‐induced diffusion wake in quark-gluon plasma in high‐energy heavy-ion collisions. We generalize this observable to other jet configurations such as $\gamma /Z^0$ jets and propose a new method to compute the rapidity asymmetry that is free of background. In this new method, the rapidity of the trigger is fixed or restricted to a symmetrical range while the rapidity of the associated jet is varied. The rapidity asymmetry is defined as the difference between the hadron rapidity distribution in the opposite azimuthal direction of the jet (or the same direction of the trigger) with different associated jet rapidities. Since the background in this hadron rapidity distribution with different associated jet rapidity is identical, it will be completely canceled in the rapidity asymmetry. Such background-free rapidity asymmetry caused by jet-induced diffusion wake is demonstrated in CoLBT-hydro simulations of dijets and $\gamma$-jets in $\mathrm{Pb}+\mathrm{Pb}$ collisions at the CERN Large Hadron Collider, which weakens as hadron $p_T$ increases, and subtraction of a $p+p$ baseline has a negligible effect.

We formulate a microscopic theory to calculate cross section of the radiative neutron capture on neutron-rich nuclei using the continuum quasiparticle random-phase approximation. This formulation is designed to be applied to neutron-rich nuclei around the $r$-process path, for which the compound nuclear model may not be appropriate. It takes into account effects of various excitation modes such as the soft dipole excitation, the giant resonances, and the quasiparticle resonance in addition to the surface vibrations such as quadrupole and octupole modes. We perform numerical calculations to demonstrate new features of the present theory, employing reactions ${}^{89}\mathrm{Ge}(n,\gamma ){}^{90}\mathrm{Ge}$ and ${}^{91}\mathrm{Zn}(n,\gamma ){}^{92}\mathrm{Zn}$ with $E1$ transitions populating the ground state, collective $2_1^{+}$ and $3_1^{-}$ states in ${}^{90}\mathrm{Ge}$ and ${}^{92}\mathrm{Zn}$. With these examples, we discuss enhanced resonance contributions in the $(n,\gamma )$ reaction at low energy, which originate from the quasiparticle resonance and the pygmy quadrupole resonance located just above the one neutron separation energy, and from combination with the low-lying octupole vibrational state.

Single-nucleon transfer reactions offer a valuable way to probe nuclear structure. We explore the effect of directly introducing overlap functions computed using the Gamow shell model (GSM) into reaction calculations, taking the ${\langle }^7\mathrm{Li}\mid {}^6\mathrm{He}+p\rangle$ single-proton overlap as a case study. By incorporating both internucleon correlations and continuum coupling, the GSM provides accurate overlap functions in both interior and asymptotic regions, together with the corresponding spectroscopic factors (SFs). These theoretical SFs and overlap functions were included in a coupled-channels Born-approximation analysis of the ${}^6\mathrm{He}{}^7\mathrm{Li}$ transfer reaction. Overlap functions derived from ab initio no-core shell-model (NCSM) calculations as well as standard single-particle (s.p.) wave functions were also considered for comparison. Our results reveal significant differences between the calculated angular distributions when employing theoretical SFs with standard s.p. wave functions compared to the full theoretical overlap functions. Discrepancies were also observed between angular distributions calculated with GSM and NCSM overlap functions, highlighting the importance of internal structure and correct asymptotic behavior in reliable reaction calculations. The GSM overlap functions also provided a good description of the ${}^{208}\mathrm{Pb}{(}^7\mathrm{Li}{,}^6\mathrm{He}$)${}^{209}\mathrm{Bi}$ reaction when included in a coupled reaction-channels calculation.

The production of light hypernuclei in relativistic heavy-ion collisions provides a unique opportunity to probe hyperon-nucleon interactions and possible three-body forces, which are central to the resolution of the hyperon puzzle in neutron star matter. In this work, we develop a data-guided coalescence framework in which the source size is extracted from proton and deuteron yields and used, together with measured proton and $\mathrm{\Lambda }$ spectra, to predict the production of $A=3$ nuclei $(t,{}^3\mathrm{He})$ and hypernuclei $\left({}_{\mathrm{\Lambda }}^3\mathrm{H}\right)$ in $\sqrt{s_{NN}}=3–200\mathrm{GeV} \mathrm{Au}+\mathrm{Au}$ collisions. For tritons, calculations with a Gaussian wave function reproduce experimental spectra and yield ratios across this energy range. For the hypertriton, the model predictions are highly sensitive to the assumed wave function. This sensitivity is strongest at low collision energies and in low-multiplicity environments, implying that such conditions are particularly valuable for probing hypernuclear structure.

Based on an extended nuclear statistical equilibrium model, we investigate the properties of nonaccreted crusts of young and warm neo-neutron stars, i.e., of finite-temperature inhomogeneous dense matter in beta equilibrium. An interesting feature is the appearance, in the deep inner crust, of an extensive and almost pure layer of neutron-rich light nuclei that extends up to the density of the transition to homogeneous matter. Most probably, this layer emerges due to translational degrees of freedom of the nuclei. If confirmed, it will significantly impact the transport and elastic properties of the crust and its crystallization process. Then we demonstrate that our inner crust is stable with respect to the diffusion of ions, which is in contrast with some of the predictions made in the literature for cold crusts. Finally, we show that clusterization completely exhausts the density instabilities that affect subsaturated nuclear matter.

Fission product yields (FPY) constitute critical infrastructure data for a wide range of nuclear applications. Accurately predicting FPY remains a significant challenge both experimentally and theoretically. Drawing inspiration from recent advancements in Bayesian neural networks within nuclear physics, as demonstrated by Wang et al. [Phys. Rev. Lett. 123, 122501 (2019)], we propose a physics-guided approach utilizing a multilayer perceptron that achieves highly accurate predictions of nuclear fission yields. The engineering and analysis of the network validate the robustness of this physics-driven neural network methodology for FPY. This approach also provides uncertainty quantification for the predicted yields. These findings underscore the effectiveness of machine learning in nuclear FPY prediction, enhancing the accuracy and reliability of theoretical models, and offering valuable insights for experimental scientists.

Background: Quasifission substantially hinders the formation of the compound nucleus in heavy ion fusion reactions. It poses a major obstacle to superheavy element formation. This process has a strong entrance channel dependence.

Purpose: To study the interplay between fission and quasifission in ${}^{30}\mathrm{Si}+{}^{197}\mathrm{Au}$ reaction at energies around the Coulomb barrier.

Methods: Binary fragments from ${}^{30}\mathrm{Si}+{}^{197}\mathrm{Au}$ reaction were measured in coincidence using a pair of large area multiwire proportional counters. The mass-ratio and mass angle distributions of the fragments were obtained using the kinematic re-construction method. Experimental results are interpreted using different theoretical methods. Further, the results of present reaction have been compared with that of ${}^{28}\mathrm{Si}+{}^{197}\mathrm{Au}$ reaction available in literature.

Results: Broadened mass ratio distributions have been observed in the range of energy studied compared to the theoretical calculations assuming compound nucleus formation. No mass angle correlation is observed. Fission fragment mass distribution of the present reaction is compared with that of other neptunium isotopes at low excitation energies. A fast transition from asymmetric fission to symmetric fission is observed with decrease of $N/Z$ along the isotopic chain of neptunium. The difference between the asymmetric and symmetric fission barrier is higher for the ${}^{238}\mathrm{Np}$ at all temperatures, compared to ${}^{225,227}\mathrm{Np}$ resulting in asymmetric mass division in the fission of ${}^{238}\mathrm{Np}$ and symmetric split at low excitation energies in ${}^{225,227}\mathrm{Np}$. Calculated quasifission yields in the mass range $80\le A\le 150$ show significant dependence on collision energy for both ${}^{28,30}\mathrm{Si}+{}^{197}\mathrm{Au}$ reactions.

Conclusions: Measured fragment mass distribution has significant contribution from slow quasifission in ${}^{30}\mathrm{Si}+{}^{197}\mathrm{Au}$ reaction. $40–60\%$ fusion probability is obtained for the ${}^{28,30}\mathrm{Si}+{}^{197}\mathrm{Au}$ reactions. Quasifission yields show strong dependence on energy and angular momentum.

This study investigates the influence of $\alpha$-cluster structures in relativistic light nuclear collisions. Using a cluster framework, I extract the characteristics of the nucleonic configurations of ${}^{16}\mathrm{O}$ and ${}^{20}\mathrm{Ne}$ as predicted by various ab initio models, including Nuclear Lattice Effective Field Theory (NLEFT), Variational Monte Carlo (VMC), and the Projected Generator Coordinate Method (PGCM). Additionally, I analyze configurations derived from a three-parameter Fermi (3pF) density function. The investigation focuses on the effects of cluster parameters on two-point correlators using a rotor model for symmetric collisions (${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ and ${}^{20}\mathrm{Ne}+{}^{20}\mathrm{Ne}$) and asymmetric collisions (${}^{208}\mathrm{Pb}+{}^{16}\mathrm{O}$ and ${}^{208}\mathrm{Pb}+{}^{20}\mathrm{Ne}$). The cluster parameters are determined by minimizing the chi-square statistic to align the nucleon distributions with those predicted by the aforementioned theories. The results reveal that perturbative calculations effectively capture the structural features of these nuclei, while comparisons with Monte Carlo simulations validate these findings. Furthermore, the analysis reveals distinct cluster geometries: VMC suggests tetrahedral shapes, while NLEFT, PGCM, and 3pF indicate irregular triangular pyramids. Notably, NLEFT shows a bowling-pin-like $\alpha$ cluster structure for ${}^{20}\mathrm{Ne}$. The study also identifies constraints on cluster parameters in the different oxygen structures, with a gradual increase in ${\varepsilon }_2\left\{2\right\}$ for the states of $\alpha +{}^{12}\mathrm{C}$. Accurate modeling of asymmetric collisions necessitates a range of nucleons from heavy spherical nuclei, leading to weighted correlators in perturbative calculations. I demonstrate consistency between perturbative calculations and Monte Carlo models, with analytical calculations providing more insights into asymmetric collisions than symmetric collisions.

We investigate medium-induced modifications to jet substructure observables that characterize hard components in central Pb-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. Using a multistage Monte Carlo simulation of in-medium jet shower evolution, we explore flavor-dependent medium effects through simulations of inclusive and $\gamma$-tagged jets. The results show that quark jets undergo a nonmonotonic modification compared with gluon jets in observables such as the Pb-Pb to $p\text{−}p$ ratio of the soft drop prong angle $r_g$, the relative prong transverse momentum $k_{T,g}$, and the groomed mass $m_g$ distributions. Due to this nonmonotonic modification, $\gamma$-tagged jets, enriched in quark jets, provide surprisingly clear signals of medium-induced structural modifications, distinct from effects dominated by selection bias. Further systematic studies demonstrate that these effects are dominated by recoil medium response. This work highlights the potential of hard substructures in $\gamma$-tagged jets as powerful tools for probing the jet-medium interactions in high-energy heavy-ion collisions, in particular by enabling detailed investigations of jet-medium parton scatterings via their associated medium response. All simulations for $\gamma$-tagged jet analyses carried out in this paper used triggered events containing at least one hard photon, which highlights the utility of these observables for future Bayesian analysis.

Using the expansion of Zubarev's density operator, we develop a linear response approach to study various spin physics in a locally equilibrated medium, particularly focusing on various polarization phenomena in heavy-ion collisions. Specifically, we connect familiar correlation functions and diagrammatic methods to the Zubarev formalism, enabling the use of established techniques like the Matsubara–imaginary time formalism to facilitate calculations. For a spin-1/2 particle, we rederive its vector polarization using this Zubarev response approach, which exactly reproduces with our previous results based on Luttinger's method. For a spin-1 particle, we calculate the vector polarization and find the expected contributions from vorticity, temperature gradients, and shear, which are identical to those for spin-1/2 particles except for a factor of 4/3 as expected. For the tensor polarization and spin alignment of a spin-1 boson, we explicitly prove that the nondissipative contribution is zero at leading order in gradients and briefly reiterate our previous findings for the dissipative contribution with further discussions on several concerns. Additionally, we discuss several relevant subtleties and questions, including an alternative derivation for Zubarev response approach, the covariance issues of different spin density matrix definitions, a further explanation of slow and fast modes, the mode selection scheme, and so on. We also discuss skeleton expansions, higher-order contributions, and nonperturbative methods, particularly their potential connection to lattice field theory. In summary, this work discusses the foundations and subtleties of Zubarev response approach, with specific examples from spin physics in heavy-ion collisions.