Within the isospin-dependent quantum molecular-dynamics (IQMD) framework, we investigate the multiplicity information entropy $H$ of neutrons, protons, intermediate-mass fragments (IMFs), and all fragments, together with the $\mathrm{\Delta }$-scaling behaviors, in central ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ collisions over an incident energy range of $E=20–350\mathrm{MeV}/\mathrm{nucleon}$. The information entropy of IMFs exhibits a plateau around $E=110$ MeV/nucleon, while that of all fragments shows a pronounced turning point at a similar energy. When considered together with other observables, these features reflect a correlated change in fragment production dynamics in this energy region. In contrast, the $\mathrm{\Delta }$-scaling analysis of the largest fragment charge $Z_{\max }$ does not indicate a transition from $\mathrm{\Delta }=1/2$ to $\mathrm{\Delta }=1$ over the same energy range. However, the charged-fragment multiplicity exhibits distinct $\mathrm{\Delta }$-scaling behaviors in low- $(E=20–80\mathrm{MeV}/\mathrm{nucleon})$ and high-energy $(E=100–350\mathrm{MeV}/\mathrm{nucleon})$ regions. These combined observations suggest that the multiplicity information entropy and the $\mathrm{\Delta }$-scaling behavior of charged fragments consistently reflect a coherent change in the fragmentation dynamics around $E=110$ MeV/nucleon.

A negative muon captured by an actinide cascades down through the muonic atomic levels; deeply bound transitions can proceed via inverse internal conversion, depositing the muonic transition energy directly into the nucleus and, when the deposited energy exceeds the fission barrier, inducing prompt fission. Because the muon mean lifetime exceeds the saddle-to-scission timescale by orders of magnitude, the muon can survive the entire fission event as a $1s$ spectator and ultimately attach to one or both of the emerging fragments. Its postscission attachment probability to the light fragment, $P_L$, can be used as a direct electromagnetic probe of fission dynamics on a timescale of ${10}^{-21}\mathrm{s}$. In previous work, we introduced a three-dimensional lattice solution of the time-dependent Dirac equation coupled to the electromagnetic field generated by a fissioning nucleus and reported $P_L$ for several actinides at a single dissipation strength. Here we extend that framework to a systematic survey of ${}^{232}\mathrm{Th}, {}^{238}\mathrm{U}$, and ${}^{240}\mathrm{Pu}$ and implement a more realistic fission model which incorporates dynamic pairing correlations. We find that $P_L$ falls steeply with the fragment charge asymmetry, a robust structural fingerprint of the fissioning system, while its dependence on nuclear dissipation is secondary and sensitive to the phenomenological friction prescription. These results establish $P_L$ as a clean electromagnetic probe of fragment charge asymmetry and motivate a self-consistent, coordinate- and time-dependent treatment of nuclear dissipation as the natural next step.

Platinum radioisotopes are of growing interest for targeted cancer therapy and diagnostic imaging because their decay delivers highly localized radiation doses in tissue, herewith enabling precise DNA damage through Auger-electron emission. Developing production technologies that provide platinum isotopes with high specific activity is essential in radioisotope therapy. Photonuclear reactions on stable nuclei offer a viable accelerator-based route for isotope production when supported by reliable cross-section data. We report photonuclear cross-section measurements for the ${}^{197}\mathrm{Au}(\gamma ,pn){}^{195m}\mathrm{Pt}$ reaction at incident $\gamma$-ray energies of 27, 29, and 31 MeV using the activation method. The measurements were performed by irradiating a stack of concentric-ring gold targets with a quasimonoenergetic $\gamma$-ray beam provided by the High Intensity Gamma-ray Source ($\mathrm{HI}\gamma \mathrm{S}$). The induced ${}^{195m}\mathrm{Pt}$ activity was quantified using offline $\gamma$-ray spectroscopy. These data provide the first experimental constraints on the ${}^{197}\mathrm{Au}(\gamma ,pn){}^{195m}\mathrm{Pt}$ cross section in the near-threshold region. The comparison of the measured excitation function to phits and talys calculations indicates that the reaction becomes measurable only near 30 MeV and that substantially higher bremsstrahlung end-point energies are required for practically meaningful production.

At the keV-scale energies of stellar nucleosynthesis, the resonant charged-particle reactions addressed by the Trojan-horse method (THM) proceed through isolated near-threshold resonances, so the low-energy cross section and the resonance strength carry the same information. The standard THM working formula is used there as a fixed extraction prescription, without a controlled reduction from the inclusive nonelastic breakup parent that would identify what it sets aside. I derive the sub-Coulomb resonant THM extraction directly from the Ichimura-Austern-Vincent inclusive nonelastic breakup cross section. A diagonal isolated-pole spectral ansatz for the absorptive participant-target potential, with four explicit validity conditions, reduces the inclusive cross section in the isolated-resonance limit to a per-pole distorted-wave Born approximation cross section on the resonance state, retaining full distortions and the postform interaction and weighted by the channel branching ratio; this is the operational quantity for resonance-strength extraction. The same one-level total-width profile follows independently from the postform transfer amplitude through the exact final states, so the extraction is route independent; a three-layer width analysis fixes its absorptive strength as half the nonelastic decay width, resolving the width and sign ambiguities of the literature. The standard factorized THM formula then follows under three dynamical approximations, plane waves, on-shell binary amplitude, and remnant neglect, together with a zero-range simplification of the projectile vertex, making explicit what it sets aside: the partial-wave coherence and the postform remnant.

We study the sensitivity of anisotropic flow in $\mathrm{Pb}+\mathrm{Pb}$ collisions at $\sqrt{s_{NN}}=5.02$ TeV to the neutron skin of ${}^{208}\mathrm{Pb}$ using the improved string-melting version of a multiphase transport (AMPT) Model. By varying the neutron surface diffuseness, we trace the impact of several neutron-skin scenarios from the initial nuclear density profiles and eccentricities to final-state charged-particle production and flow cumulants. A systematic response is observed in both the initial eccentricities and the anisotropic flow, indicating that the neutron-skin-induced geometric effects can survive the full transport evolution. A model-to-data comparison with ALICE measurements disfavors the most compact and most diffuse density profiles within the tested AMPT setup, while the reference and moderate-skin configurations give comparable descriptions. Their similarity reflects a geometric degeneracy in large $\mathrm{Pb}+\mathrm{Pb}$ collision systems, where the inclusive anisotropic flow is dominated by the effective collision geometry and nuclear size, making it only weakly sensitive to the detailed structure of the neutron surface. These results clarify both the sensitivity and the limitations of using anisotropic flow in relativistic heavy-ion collisions to probe neutron-skin effects.

We present an upgraded formula for Wigner function and spin polarization of fermions emitted by a relativistic fluid at local thermodynamic equilibrium at the decoupling, which improves the one obtained by F. Becattini, M. Buzzegoli, and A. Palermo [Phys. Lett. B 820, 136519 (2021)] and by S. Y. F. Liu and Y. Yin [J. High Energy Phys. 07 (2021) 188] that is used in numerical simulations of relativistic nuclear collisions. By using a new expansion method, applicable to decoupling hypersurfaces with arbitrary geometry, we reproduce the known term proportional to thermal vorticity and obtain an upgraded form of the spin-shear term which captures the dependence on the geometry. The new method also includes additional contributions whose physical nature is to be assessed. The new expression also naturally excludes contributions from space-time gradients in the normal direction of the hypersurface, providing a theoretical justification for the isothermal condition previously imposed a priori. This framework can be extended to particles with arbitrary spin.

The simultaneous observation of strong sequential bottomonium suppression and small azimuthal anisotropy constrains the time scale and geometry of quarkonium dissociation in relativistic heavy-ion collisions. This work investigates an early-time contribution in which strong pre-equilibrium color fields generate an effective proper-acceleration scale and an associated causal length. The maximal acceleration is fixed through the phenomenological anchoring assumption $T_U^{max}\simeq T_c$, without identifying the kinematic Unruh scale with an equilibrium temperature. The survival probability is described by an event-averaged one-scale exponential ansatz. With no state-by-state adjustment, the resulting horizon component gives a quantitatively reasonable description of the LHC centrality dependence. For the directly measured $\mathrm{{\rm Y}}\left(2S\right)$-to-$\mathrm{{\rm Y}}\left(1S\right)$ double ratio, the fixed horizon term supplies a substantial part of the relative suppression, while the data require an additional state-dependent late-stage factor. A minimal one-parameter effective quark-gluon plasma (QGP) attenuation gives a quantitative multistage description. At RHIC, the absolute $R_{AA}$ central values lie below the isolated horizon component, while the relative $2S$-to-$1S$ suppression remains compatible with the predicted state-size hierarchy within present uncertainties. Because the proposed early factor is local and scalar, it gives the exact leading-order null contribution $v_2^H=0$ within this construction, consistent with current CMS measurements.

Relativistic ${}^{16}\mathrm{O}+{}^{16}\mathrm{O}$ collisions provide a valuable opportunity to study both the quark-gluon plasma formed in small systems and the intrinsic structure of ${}^{16}\mathrm{O}$. Recent implementations of ab initio nuclear configurations in heavy-ion simulations have produced different predictions for cluster-sensitive observables, making it difficult to identify the origin of possible $\alpha$-cluster signals. In this work, we introduce a controlled sampling scheme that varies the compactness of $\alpha$-cluster-induced multinucleon correlations while keeping the one-body density distribution of ${}^{16}\mathrm{O}$ fixed. This allows us to separate effects driven by the tetrahedral one-body density from those driven by genuine multinucleon correlations. We show that the normalized ratios $\mathrm{Norm}(v_2\left\{2\right\}/v_2\left\{4\right\})$ and $\mathrm{Norm}(v_2\left\{2\right\}/v_3\left\{2\right\})$, together with their initial-state eccentricity counterparts, provide complementary constraints on initial-condition model dependence and cluster compactness. Hybrid hydrodynamic simulations and comparisons with recent LHC measurements further clarify the extent to which the initial-state signals survive final-state evolution. Our results provide a framework for using relativistic light-ion collisions to constrain cluster correlations in ${}^{16}\mathrm{O}$.

We present a new formulation for the mean-field propagation part of relativistic quantum molecular dynamics, simulating an $N$-body system of interacting Gaussian wave packets via Lorentz scalar and vector potentials. Covariant equations of motion are derived based on the principle of least action with a weak form of mass-shell conditions and time-fixation constraints defined with respect to a chosen foliation. However, as is common with traditional relativistic quantum molecular dynamics, the dynamics exhibits a residual dependence on the chosen foliation, which is unavoidable because a finite number of interacting degrees of freedom is not strictly compatible with relativity. Nevertheless, we show that this dependence remains small for physically reasonable choices of the foliation in practical applications. By introducing a new approximation method to the spatial integral in the equations of motion, these covariant equations of motion can be solved with a computational cost comparable to that of conventional noncovariant quantum molecular dynamics. Furthermore, the new equations of motion accurately estimate the density-dependent potential, as demonstrated through comparison of the forces with the numerical integration. We apply them to $N$-body systems interacting via the Skyrme-type potentials or the relativistic mean field to simulate heavy-ion collisions. Our results show that the derived equations of motion provide a robust approximation to the dynamics of the full numerical integrations.

The correlation between vorticity and spin alignment in heavy-ion collisions can be probed through polarization measurements of hadrons, whose total spin originates from both constituent-quark spins and orbital angular momentum in the quark-model framework. So far, experimental measurements have been limited to $\mathrm{\Lambda }$ baryons and vector mesons, whose total spins are composed of quark spins in $s$-wave states within the quark model. Here, as a means to probe the vorticity structure in heavy-ion collisions, we highlight the importance of studying hadrons whose total spin is composed not only of quark spins but also includes contributions from the orbital angular momentum between quarks. To motivate such experimental studies, we calculate the general angular distribution of produced pion in $f_2\left(1270\right)\to \pi +\pi$ using interaction Lagrangian and helicity formalism and check that both methods yield the same result. The distribution is given as a function of angle between pion and initial quantization axis of $f_2$ and the spin-density matrix element of $f_2$. Its diagonal entries and ${\rho }_{20}$ component were computed assuming local thermal equilibrium and blast-wave model for different centrality classes, hence given as a function of azimuthal angle with respect to the impact parameter. This is to set a baseline for future comparison with experiment, as vorticity and spin will, in general, not be in equilibrium.

In this work, we discuss the $\gamma W$-exchange contributions in neutron $\beta$ decay with an elastic intermediate state, beyond the forward-angle limit (FAL). By decomposing the one-$W$-exchange and $\gamma W$-exchange amplitudes in terms of 16 independent Pauli-spinor structures, we calculate the $\gamma W$-exchange corrections to the relevant coefficients. Our numerical results show that the relative corrections to the Fermi Born term $C_{\text{Born}}^{\text{F}}$ and the Gamow-Teller Born term $C_{\text{Born}}^{\text{GT}}$ are enhanced by about 8% and 18%, respectively. In particular, we find a nonzero contribution to $C_{\text{Born}}^{\text{GT}}$ from the axial-vector current, which is identically zero in the FAL. The corresponding effect on the extracted $V_{ud}$ from the neutron lifetime is also analyzed, and we find the correction to be at the ${10}^{-4}$ level.

The astrophysical $S^{*}\left(E\right)$ factor for the ${}^{12}\mathrm{C}+{}^{12}\mathrm{C}$ reaction within the Gamow window ($E_G=1.5\pm 0.3$ MeV) plays a pivotal role in modeling stellar carbon burning and explosive nucleosynthesis scenarios. However, direct measurements—or even simple extrapolations—at these energies are severely hindered by Coulomb suppression and the possible presence of narrow resonances. To address this challenge, we performed an indirect measurement of the ${}^{12}\mathrm{C}({}^{16}\mathrm{O},\alpha \mathit{p}){}^{23}\mathrm{Na}$ reaction at the HI-13 Tandem Accelerator, employing ${}^{16}\mathrm{O}=({}^{12}\mathrm{C}\oplus \alpha )$ as the Trojan horse nucleus. A key innovation of this Trojan horse method (THM) study is the implementation of a copper beam-stopper foil, which enabled the detection of spectator particles near $0^{\circ }$ –the angular region where their yield is maximized under quasi-free kinematics. The $S^{*}\left(E\right)$ factor for the ${}^{12}\mathrm{C}({}^{12}\mathrm{C},\mathit{p}){}^{23}\mathrm{Na}$ reaction in the astrophysically relevant energy range was extracted using the THM formalism based on the distorted-wave Born approximation (DWBA). Our results confirm the presence of resonant structures within the Gamow window around 1.5 MeV in both the $p_0$ and $p_1$ proton channels. No evidence of a hindrance effect is observed in the measured energy range. Without considering the resonance details, the overall trend of our results is qualitatively in reasonable agreement with the THM-Tumino2018 and TTIK2025 data, but differs significantly from the trend of the Modified-THM-Muk2019 data.

We investigate neutron star matter with hyperons within a density-dependent relativistic mean-field framework using Bayesian inference, considering three composition scenarios: purely nucleonic matter, hyperonic matter under SU(6) flavor symmetry, and hyperonic matter under SU(3) symmetry with free vector-sector parameters. The analysis incorporates constraints from empirical nuclear matter properties, theoretical inputs at low densities, and multimessenger observations of neutron stars. We find that the SU(6) scheme, grounded in the quark model and isospin counting rule, leads to a significantly softer equation of state. In contrast, the additional flexibility of the SU(3) framework enhances vector repulsion and yields a comparatively stiffer equation of state consistent with observational bounds across the explored parameter space; in particular, the posterior distributions favor values of the vector coupling ratio ${\alpha }_v$ lower than the SU(6) limit ${\alpha }_v=1$. These differences are reflected in neutron star observables, including mass-radius relations, tidal deformabilities, direct Urca thresholds, and oscillation properties, all of which remain compatible with current constraints within the SU(3) scenario. We further examine structural signatures through the curvature of the mass-radius relation and find that, although hyperon-rich configurations can induce noticeable variations, such features depend sensitively on the stiffness of the equation of state and are therefore not universally robust indicators. Bayesian model comparison further shows that present constraints do not meaningfully discriminate between the purely nucleonic and SU(3) hyperonic scenarios, while providing positive, but not decisive, evidence against the more restrictive SU(6) framework.

Gravitational-wave observations have renewed interest in the black-hole mass gap and in the maximum mass of first-generation black holes below its lower edge. The ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O}$ reaction plays a central role in this problem because it determines the carbon-to-oxygen ratio after core-helium burning and thereby affects the later evolution of massive stars toward pulsational pair instability and pair-instability supernovae. Recent attempts to constrain $S\left(300\mathrm{keV}\right)$ from gravitational-wave population inferences face important limitations, because the lower edge of the black-hole mass gap is not directly measured. It is inferred model dependently from assumptions about stellar evolution, metallicity, mass loss, rotation, binary evolution, hierarchical mergers, selection effects, priors, and the adopted population model. Therefore, values of $S\left(300\mathrm{keV}\right)$ inferred from black-hole populations must remain consistent with independent nuclear-physics constraints. In this work the low-energy ${}^{12}\mathrm{C}(\alpha ,\gamma ){}^{16}\mathrm{O} S$ factor is reanalyzed using updated information on the subthreshold $1^{-}$ and $2^{+}$ asymptotic normalization coefficients (ANCs) and on the ground-state ANC of ${}^{16}\mathrm{O}$, together with direct capture data. These constraints favor a lower $S\left(300\mathrm{keV}\right)$ than the older central evaluation and disfavor very large values required by some black-hole-population interpretations. Combining the resulting ANC-constrained $S\left(300\mathrm{keV}\right)$ range with the transformed relation between this quantity and the lower edge of the pair-instability mass gap gives $\frac{M_{\mathrm{BH}}}{M_{\odot }}\simeq 61-75$. Thus, the present nuclear-physics constraints favor a relatively high lower edge of the first-generation black-hole mass gap.

We employ the three-body model to the ${}^{12}\mathrm{Be}$ nucleus by solving the Faddeev equations in momentum space using the partial-wave decomposition method. Four sets of interactions between the ${}^{10}\mathrm{Be}$ core and the neutron, $V_{cn}$, are constructed in different ways to test the validity of the three-body model. The spectra of ${}^{12}\mathrm{Be}$ are obtained, including the $0_1^{+}, 2^{+}, 1^{-}, 0^{-}$, and $0_3^{+}$ states, together with the rms radii, $R_m$. Our results are consistent with previous three-body computations of ${}^{12}\mathrm{Be}$ in coordinate space and the most recent ab initio calculations. For the $0_1^{+}$ ground state, the energies and radii of four sets of $V_{cn}$ are close to the experimental data. In particular, when $V_{cn}$ is constructed close to the realistic core-neutron interaction, the resulting probabilities of the $p$-wave configurations are similar to those obtained from earlier shell-model calculations. Additionally, we predict two excited states, $0^{-}$ and $0_3^{+}$, together with their two-neutron separation energies. For the first excited $2^{+}$ state, our calculations suggest that, if the $d_{3/2}$ and $d_{5/2}$ orbitals share the 1.28 MeV resonance state in ${}^{11}\mathrm{Be}$, then the three-body model could produce results that align with the experimental data.

We theoretically investigate a quartet superfluid state in fermionic matter by using the quartet Bardeen-Cooper-Schrieffer (BCS) variational theory and the Green's function method. We demonstrate that the quartet BCS theory with the multiple-infinite-product ansatz successfully reproduces an exact four-body result in a one-dimensional four-component Fermi gas at the dilute limit, in contrast to the single-infinite-product ansatz. To see the validity of the quartet BCS state, we derive the self-consistent equation for the quartet superfluid order parameter within the generalized imaginary-time Nambu-Gor'kov formalism, which is found to be consistent with the quartet BCS variational equation. Moreover, by numerically computing the momentum-resolved single-particle spectral function in a one-dimensional system, we discuss how the single-particle spectra evolve with increasing the strength of the four-body cluster formation. We show that a coherent BCS-like quasiparticle branch on the weak-coupling side evolves into a strongly damped, continuum-dominated spectrum in the strong-coupling side, while nonzero quartet superfluid order parameter persists throughout the crossover regime. Our results would be useful for understanding beyond-BCS pairing effects and four-body cluster formations in fermionic systems in an interdisciplinary way.

To study the isoscalar giant resonances in a deformed case, background-free $\alpha$-particle inelastic scattering measurements using a 386 MeV $\alpha$ beam were performed on the highly deformed ${}^{172}\mathrm{Yb}$ nucleus using the Grand Raiden spectrometer at the Research Center for Nuclear Physics (RCNP) at very forward angles, including $0^{\circ }$. The strength distributions for the isoscalar giant resonances up to $L\le 3$ were obtained using multipole decomposition analysis. The isoscalar giant monopole resonance (ISGMR) strength exhibits a splitting into two components, interpreted as the coupling of the ISGMR with the $K=0$ component of the isoscalar giant quadrupole resonance (ISGQR). A bimodal structure is observed in the strength distribution of the isoscalar giant dipole resonance. The ISGQR strength shows an enhancement near 25 MeV, attributed to the excitation of an overtone mode, while the broadening of the main-tone peak is associated with nuclear deformation. The experimental results are compared with theoretical strength distributions calculated using the quasiparticle finite amplitude method for $L\le 3$.

We develop a generalized finite-temperature proton-neutron BCS framework using the superoperator formalism, incorporating both isovector and isoscalar monopole pairing channels. Numerical calculations for a schematic equidistant multilevel model and realistic even-even Ge isotopes demonstrate the emergence of proton-neutron ($pn$) pairing reentrance in even-even asymmetric ($N>Z$) nuclei with preexisting like-nucleon pairing correlations. This nonmonotonic behavior arises from thermal excitations that partially lift Pauli blocking of single-particle orbitals near the chemical potentials, thereby enlarging the phase space for $pn$ pair formation. We uncover a delicate interplay between thermal unblocking and like-nucleon pairing, which can either suppress or enhance $pn$ correlations depending on temperature and shell filling. A qualitative analysis of Fermi charge-exchange strength functions in hot ${}^{72}\mathrm{Ge}$, which neglects the residual interaction between thermal quasiparticles, suggests that $pn$ pairing reentrance may alter the transition strength distribution around $T\approx 1$ MeV. This indicates that finite-temperature $pn$ correlations could potentially impact stellar weak-interaction rates in $rp$-process and supernova environments.