A microscopic study of $\alpha$-decay half-lives is performed to examine the influence of the nuclear medium effect on the $\alpha$-daughter interaction. The conventional double-folding potential is improved by replacing the fixed free-$\alpha$ density with a density-dependent $\alpha$-cluster distribution that varies with the local density of the daughter nucleus. This modification accounts for the change of the $\alpha$-cluster size induced by Pauli blocking and the surrounding nuclear mean field during the decay process. Because $\alpha$ decay is highly sensitive to the surface region of the interaction potential, the medium-induced modification of the $\alpha$ density has a direct impact on the barrier penetrability and calculated half-lives. The calculations are carried out for a wide range of 256 nuclei, with special attention to isotopic chains around shell closures in order to clarify the role of magicity in $\alpha$-decay systematics. Nuclear deformation is included through deformed daughter-density distributions, and its effect on the orientation-dependent potential and half-life is investigated. The influence of the exchange part of the effective nucleon-nucleon interaction is also analyzed by comparing zero-range and finite-range exchange treatments of the M3Y-Paris interaction. The results show that the nuclear medium effect improves the description of experimental half-lives, while deformation and finite-range exchange provide additional refinements, especially for open-shell and deformed nuclei. The observed behavior around magic numbers confirms the strong connection between shell structure, $\alpha$-cluster formation, and decay probability. These findings indicate that the combined treatment of medium effects, deformation, and exchange interaction is important for a reliable microscopic description of $\alpha$ decay.

Low-spin excited states in ${}^{68}\mathrm{Zn}$ have been studied at the High Intensity Gamma-Ray Source ($\mathrm{HI}\gamma \mathrm{S}$) from the ground state up to the particle emission threshold using the nuclear resonance fluorescence technique and the newly developed clover array. Low-spin levels were excited by linearly polarized, 2.90–9.79 MeV photon beams. Spin-parity quantum numbers as well as associated $M1$ and $E1$ decay strengths were determined for a large fraction of the 158 states observed. In addition, long-duration coincidence measurements at 9.46 and 9.79 MeV enabled the investigation of the level scheme near the ground state. The results have been interpreted with shell-model calculations using two different model spaces and several effective interactions often used to describe nuclei in this mass region. While the structure near the ground state can be understood in terms of excitations involving solely valence nucleons, core breaking is required to account for the evolution of the total $M1$ strength at excitation energies above approximately 5 MeV.

Background: Mass-asymmetric fission in the actinide nuclei is dominated by shell gaps in the heavy fragment, proposed to be due to octupole deformed shell gaps between $Z=52$ and 56. The mass-asymmetric fission of nuclei lighter than lead shows the influence of different shell gaps, centered around $Z=34,36$ and $Z=44,46$. There is indirect evidence that the $Z=44$ shell gap may influence fission in isotopes as heavy as ${}^{240}\mathrm{Pu}$.

Purpose: Examine the fission modes present in ${}^{216–221}\mathrm{Ra}$ (proton number $Z=88$) where the $Z=44$ shell gap may be expected to influence fission at mass symmetry, and investigate their evolution along the Ra chain.

Method: Fission of ${}^{216–221}\mathrm{Ra}$ was induced in the heavy-ion fusion of ${}^{12,13}\mathrm{C}$ with ${}^{204,206,208}\mathrm{Pb}$ at excitation energies between 24 and 28 MeV. Fission fragments were detected in coincidence and their mass ratios and total kinetic energies (TKEs) reconstructed.

Results: The presence of the asymmetric modes of fission near $Z=52,56$ and the presence of a mode located at symmetry ($Z=44$) with TKE higher than the wide mass-symmetric (liquid-drop) fission is established over the entire ${}^{216–221}\mathrm{Ra}$ chain. In ${}^{216–219}\mathrm{Ra}$, two-dimensional mass-ratio-TKE fits suggest the additional influence of fission driven by $Z=46$ and/or its complementary fragment at $Z=42$.

Conclusions: High-statistics measurements of heavy-ion fusion-fission, combined with statistically rigorous analysis, enables high-fidelity decomposition into Gaussian fission modes, even at relatively high excitation energies. Consistent evidence for a high-TKE shell-driven mode at $Z=44$ contributes to a growing body of evidence that the $Z=44$ mode shell gap is important both in the preactinides and in the actinides, and to the idea that bimodal symmetric fission may occur whenever a favorable shell gap coincides with mass symmetry.

The synthesis of superheavy nuclei (SHN) through fusion reactions is a critical area of nuclear physics, offering insights into nuclear stability and the limits of the periodic table. However, theoretical predictions of evaporation residue cross sections ${\sigma }_{\mathrm{ER}}$ remain challenging due to large uncertainties arising from complex reaction mechanisms and sensitive model parameters. In this work, the average production probabilities of SHN with atomic number $Z\ge 110$ are systematically analyzed, based on the barrier tunneling concept. Together with the empirical barrier distribution method for describing capture, a phenomenological formula, EBD3, is proposed, which reproduces 58 measured ${\sigma }_{\mathrm{ER}}$ within one order of magnitude, with a root-mean-square deviation of 0.369. The formula successfully captures key quantities in the fissionlike process, including fission barrier height, mass asymmetry, depth of the capture pocket, and the effective fusion barrier height. Predictions for the synthesis of element 119 are presented, identifying promising projectile-target combinations such as ${}^{50}\mathrm{Ti}+{}^{249}\mathrm{Bk}$ with a maximum cross section of $54.9_{-29.0}^{+61.3}$ fb at the excitation energy of 36.5 MeV. The maximum cross section falls to $3.2_{-1.7}^{+3.6}$ fb for ${}^{54}\mathrm{Cr}+{}^{243}\mathrm{Am}$ at the optimal incident energy of 244 MeV.

The generation of fission fragment spin as a probe of scission mechanism remains a question of considerable interests. We present here microscopic calculations of rapidly rotating fission of the compound nucleus ${}^{240}\mathrm{Pu}$ under varying initial conditions within the time-dependent density functional theory framework. The obtained spin ratio of light to heavy nascent fragments is unchanged up to high spins but diminished as excitation energies increase, indicating sawtooth structures in fragment spins would fade away at high excitations rather than high angular momentum. Results also show elongated neck configurations and nonaxially symmetric deformations of fragments owing to rapid rotations. These findings offer insights into the scission mechanism of rapidly rotating compound nuclei with strong fragment spin polarizations.

Nuclear pear-shaped, or octupole, deformation enhances the sensitivity of nuclei to fundamental symmetry-violating effects, including CP violation, yet its quantitative characterization, particularly its quantum fluctuations, remains challenging. We establish a multiscale validation strategy that combines low-energy electromagnetic transitions with intermediate-energy nucleus-nucleus collisions to probe octupole deformation and its associated quantum shape fluctuations. Using a microscopic collective Hamiltonian based on density functional theory, we first reproduce the electric octupole transition strengths of ${}^{226}\mathrm{Ra}, {}^{238}\mathrm{U}$, and ${}^{244}\mathrm{Pu}$, thereby validating the underlying nuclear-structure inputs. Within the isospin Boltzmann-Uehling-Uhlenbeck transport model, we then verify the geometric response by correlating initial participant eccentricities with self-correlation-subtracted two-particle flow observables. The resulting triangular-flow observable $v_3{\left\{2\right\}}^2$ scales with the mean-square octupole deformation $\langle {\beta }_3^2\rangle$. Crucially, the event-by-event fluctuation $\sigma \left[v_3{\left\{2\right\}}^2\right]$ exhibits a robust linear correlation with the octupole quantum-shape fluctuation $\sqrt{\langle {\beta }_3^4\rangle -{\langle {\beta }_3^2\rangle }^2}$. This provides an experimentally accessible collision observable for probing quantum fluctuations associated with nuclear deformation.

This work proposes Quantum Monte Carlo (QMC) methods for interacting many-fermion systems by leveraging the stochastic gauge freedom, originally developed in Gaussian phase-space QMC, within the phaseless auxiliary-field QMC (AFQMC) framework. In particular, the approach reinterprets the conventional force bias in phaseless AFQMC as a drift gauge and explores Fermi gauges based on the natural orbitals of a reduced one-body density matrix defined via a mixed estimator, yielding stochastic, time-dependent Hartree-Fock-like dynamics. A symmetry-projection sampling scheme is also introduced to improve sampling efficiency. As a proof of concept, these gauge-augmented AFQMC methods are applied to a simple shell-model Hamiltonian: the Lipkin-Meshkov-Glick model. Numerical results illustrate the potential of stochastic gauges to enhance accuracy and reduce fluctuations, underscoring the promise for advancing these techniques toward more realistic shell-model applications.

Conventional nuclear mass formulas, predicated on the charge independence of nucleon-nucleon ($NN$) interactions, generally parametrize the neutron-proton asymmetry $[I=(N-Z)/A]$ using even powers or absolute values. Previously, an $I^3$ term was incorporated into the classical liquid drop model to examine the influence of isospin symmetry breaking (ISB) on nuclear mass. Although this term captures the ISB effect especially in the mass region of large isospin asymmetry, its directly fitted coefficient is often overshadowed by the dominant macroscopic background. This may lead to numerically entangled and physically unreasonable values, which would undermine the credibility of subsequent conclusions regarding the breaking effect. To address this issue, this paper utilizes a double-difference analysis of binding energies to extract a more physically rational coefficient for the $I^3$ term. Benefiting from the isospin-related terms, the coefficients of these terms all have been refined, during which the volume symmetry energy coefficient was readjusted to around −29 MeV. This is slightly lower than the typical results found in previous models. Furthermore, the ratio of surface symmetry energy coefficient to the volume symmetry energy coefficient is in the range of 1.6–1.8, which is in good agreement with the results reported in previous works. More importantly, the value of the ISB term coefficient, as expected, was refined to $-3.7\pm 0.65$ MeV. Although the contribution of this term to nuclear mass in the liquid drop model is small, the extracted values remain highly stable, particularly when approaching the neutron-rich region.

A consistent finite-temperature microscopic theory for the response of strongly coupled superfluid fermionic systems is formulated. We start from the general many-body Hamiltonian with the vacuum (bare) two-fermion interaction and derive the equation of motion (EOM) for the thermally averaged two-time two-fermion correlation function, which determines the spectrum of the system under study. The superfluidity is introduced via the Bogoliubov transformation of the fermionic field operators, and the entire formalism is carried out in the basis of Bogoliubov's quasiparticles, keeping the complete $4\times 4$ block matrix structure of the two-fermion EOM. Fully correlated static and dynamical interaction kernels of the resulting EOM are discussed. A special focus is then placed on the latter kernel, which is advanced to a factorized form, enabling a minimal truncation of the many-body problem while keeping important effects of emergent collectivity and mapping to the quasiparticle-vibration coupling (qPVC). As in the zero-temperature and nonsuperfluid cases, the qPVC can be associated with a new order parameter, the qPVC vertex. In the thermal superfluid theory, this vertex as well as the components of the dynamical kernel acquire an extended form including thermally unblocked transition amplitudes.

We investigate the Gamow-Teller (GT) transition strength distributions in the light carbon isotopes ${}^{12,14,16}\mathrm{C}$ within the framework of the deformed quasiparticle random-phase approximation (DQRPA). Nuclear deformation is explicitly incorporated through Skyrme-Hartree-Fock mean-field calculations combined with the QRPA formalism. The residual particle-hole $\left(\text{p-h}\right)$ and particle-particle $\left(\text{p-p}\right)$ interactions are derived from Brückner $G$-matrix calculations based on the CD-Bonn potential, and their impact on the low-lying GT strengths is systematically examined by varying the corresponding interaction strengths. We find that nuclear deformation, particularly that induced by a reduced spin-orbit strength, plays a significant role in interpreting the GT strength distribution of ${}^{12}\mathrm{C}$. In contrast, the calculated ${\mathrm{GT}}^{(-)}$ strength distribution of ${}^{14}\mathrm{C}$ in the spherical limit reproduces the essential features of the experimental $(p,n)$ charge-exchange data. The case of ${}^{16}\mathrm{C}$ reveals additional high-lying GT strength associated with deformation-induced configuration mixing.

We report measurements of the total two-neutron stripping cross section for the ${}^{197}\mathrm{Au}({}^{18}\mathrm{O},{}^{16}\mathrm{O}){}^{199}\mathrm{Au}$ reaction across the energy range $E_{\mathrm{Lab}}$ = 63–125 MeV, corresponding to $0.8\le E_{\mathrm{Lab}}/V_B^{\mathrm{Lab}}\le 1.6$. The experiment employed the stacked-foil activation technique, where eight thin gold targets were irradiated sequentially arranged in a stack by an ${}^{18}\mathrm{O}$ beam. The resulting ${}^{199}\mathrm{Au}$ activities were measured via offline $\gamma$-ray spectroscopy. The production of ${}^{199}\mathrm{Au}$ was confirmed by observing its characteristic $\gamma$ rays ($\gamma$-ray transitions in ${}^{199}\mathrm{Hg}$ following the ${\beta }^{-}$ decay of ${}^{199}\mathrm{Au}$), and further validated through decay-curve analysis of the ${}^{199}\mathrm{Au}$ half-life. Absolute cross sections for the two-neutron stripping channel were extracted and compared with theoretical model predictions. The measured cross sections increase sharply near the Coulomb barrier, from $0.96\pm 0.65$ mb at $E_{\mathrm{Lab}}/V_B^{\mathrm{Lab}}=0.80$ to approximately 40–42 mb at energies above the barrier. Theoretical calculations using the semiclassical GRAZING model systematically underestimate the data, particularly at sub-barrier energies, suggesting limitations in its treatment of pair-correlated transfer. Coupled-reaction-channel calculations performed with the $\mathrm{FRESCO}$ code indicate that two-neutron stripping mechanism is dominated mainly by simultaneous transfer of two neutrons rather than the sequential two-step process. The data are best reproduced by a cluster model with reduced spectroscopic amplitudes, pointing to the role of pairing correlations and configuration mixing in the transfer process. This work provides new absolute cross-section data for two-neutron transfer on a heavy target at sub-barrier energies and highlights challenges in current theoretical descriptions of pair-transfer reactions near the Coulomb barrier.

Background: Neutron reactions off lithium isotopes up to 50 MeV are important for nuclear data science, around the International Fusion Material Irradiation Facility (IFMIF) facility in particular.

Purpose: We aim at constructing a semimicroscopic reaction model that describes neutron elastic scattering off ${}^6\mathrm{Li}$ up to 50 MeV, taking the breakup channels of ${}^6\mathrm{Li}$ into account.

Methods: We adopt the continuum-discretized coupled-channels method (CDCC) with an $\alpha +p+n$ three-body model of ${}^6\mathrm{Li}$. We employ the $g$-matrix effective interaction by Jeukenne, Lejeune, and Mahaux (JLM). The renormalization factors of the real and imaginary parts of the JLM interaction are treated as free parameters.

Results: The renormalization parameter of the real part of the JLM interaction is found to be constant ($=1.1$), whereas that for the imaginary part has a smooth energy dependence. The four-body CDCC calculation with these parameters well describes the angular distributions of both proton and neutron elastic scatterings as well as the neutron total cross section and proton total-reaction cross section. The applicable energy range is found to be from 7 MeV to 50 MeV.

Conclusions: We have constructed a reliable reaction model for describing nucleon-${}^6\mathrm{Li}$ scattering between 7 MeV and 50 MeV. This model can directly be applied to inelastic scattering and breakup reactions for ${}^6\mathrm{Li}$ with the help of the complex scaling method.

Angular distributions for the ${}^{12}\mathrm{C}(p,p^{\prime }){}^{12}\mathrm{C}^{*}\left(7.65\mathrm{MeV}\right)$ reaction populating the Hoyle state have been measured at incident proton energies between 10.8 and 18.0 MeV. It extends the available experimental cross section data in the intermediate energy region and suggests a small resonance around 12.0 MeV. The measured cross sections along with the available data were used to evaluate the proton-induced deexcitation rates of the Hoyle state. The resulting enhancement factors for the triple-$\alpha$ reaction rate are found to differ substantially throughout the calculated temperature range, $0.1–10.0$ GK, and can be as much as $22\%$ higher than the previous estimate that relied on sparse experimental data. The observed deviation highlights the sensitivity of the enhancement to the underlying inelastic scattering cross sections. Further, the experimental data provides more reliable constraints for modeling ${}^{12}\mathrm{C}$ production in hot and dense stellar environments, especially in proton-rich astrophysical environments.

$p_t$-differential quantity $v_2\left(p_t\right)$ is meant to measure elliptic flow manifested by a dense QCD medium formed in high-energy nucleus-nucleus collisions. Elliptic flow may be referred to more neutrally as a cylindrical quadrupole component of the transverse motion of particle sources within a collision. As defined, $v_2\left(p_t\right)$ relies on an implicit assumption that almost all produced particles emerge from a single source. This article describes a detailed study of the algebraic structure of $v_2\left(p_t\right)$. A procedure is developed to derive a common monopole boost (“radial flow”) value and quadrupole $p_t$ spectra for several hadron species. The method is applied to $v_2\left(p_t\right)$ data for four hadron species from 2.76-TeV Pb-Pb collisions. According to available $v_2\left(p_t\right)$ data the assumption of a single dominant particle source within $A\text{−}A$ collisions is unjustified. Combined with a previous study of quadrupole amplitude variation for 200-GeV $p\text{−}p$ collisions these results demonstrate that quadrupole structure is related to a novel QCD process separate from projectile-nucleon dissociation and jet production. Given quadrupole evolution it is unlikely that a hydrodynamic description is relevant to that process.

We assess the effects of a recently proposed generalized relaxation time approximation (RTA) for multispecies relativistic gases within a realistic numerical hybrid framework and study its phenomenological consequences in $p$-Pb and Pb-Pb collisions. The novel approximation introduces counterterms to the collision kernel, allowing for momentum-dependent relaxation times ${\tau }_i\left(p\right)$ while preserving local energy-momentum conservation. As a consequence, the resulting first-order viscous corrections $\delta f_i$ to the phase-space distribution functions depend explicitly on the particle species mass $m_i$. We systematically investigate the impact of these species-dependent corrections on particle production at particlization, focusing on identified hadron yields and transverse momentum ($p_T$) spectra obtained from Cooper-Frye sampling. We find that the yields and spectra of light hadrons ($\pi ,K,p$) are significantly affected, leading to modifications of relative particle yields such as the $K/\pi$ and $p/\pi$ ratios. We show that these effects persist, albeit with reduced magnitude, after the inclusion of the hadronic cascade stage. In contrast, the impact on inclusive charged-particle observables is strongly reduced due to compensating enhancements and suppressions among different species. This controlled deformation of identified hadron observables, which selectively modifies flavor-sensitive quantities, makes the new prescription particularly well suited for Bayesian inference, as it introduces new sensitivity directions without spoiling existing constraints. Overall, our results demonstrate that species-dependent viscous corrections arising from the generalized RTA can leave significant and observable imprints on identified hadron production and relative yields, while remaining fully consistent with the successful description of bulk collective flow observables.

We derive the long-range components of the nucleon-nucleon (NN) two-pion-exchange potential with an intermediate Roper resonance. Leading-order interactions in heavy-baryon chiral perturbation theory are considered. To assess the Roper contributions in a unified framework, we include the leading contributions from the Delta resonance, as well as mixed Delta-Roper effects. NN phase shifts with orbital angular momentum $L\ge 2$ are calculated in first-order perturbation theory and compared to those obtained without the Roper resonance. We find that the Delta sets the dominant scale of the resonance-induced corrections, while the Roper-dependent effects are smaller, strongly channel dependent, and most visible in the $D$ waves.

We analyze 67 heavy-ion fusion reactions with high-quality sub-barrier excitation functions using the single-Gaussian model of Jiang et al. [Phys. Rev. C 112, 034612 (2025)] and extract the barrier parameters $R_g,V_g,W_g,R_g^2{W}_g$. The reactions involve seven projectiles, ${}^{16,18}\mathrm{O}, {}^{28,30}\mathrm{Si}, {}^{32,34}\mathrm{S}$, and ${}^{40}\mathrm{Ca}$, on targets from ${}^{12}\mathrm{C}$ to ${}^{208}\mathrm{Pb}$. The mean barrier height $V_g$ scales linearly with $\eta =Z_1{Z}_2/(A_1^{1/3}+A_2^{1/3})$ ($r=0.999$), while $R_g^2{W}_g$ correlates strongly with $W_g$ ($r=0.95$). The $\eta$ dependence accounts for 45% of the variation in fusion strength. After removing this geometric dependence, the resulting structure ratio $r_{\eta }$ shows no correlation with static target deformation or neutron-transfer $Q$ value. For the 24 systems with at least one open transfer channel, however, $r_{\eta }$ correlates strongly with an effective transfer coupling strength $\mathrm{\Lambda }$ ($r=0.70, p=1.4\times {10}^{-4}$), whereas the $Q$ value alone does not. Thus, positive-transfer $Q$ values are necessary but not sufficient for fusion enhancement, with the transfer coupling strength playing a key role. Systems showing the largest deviations from the geometric trend provide promising candidates for detailed coupled-channels studies.