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.

We examine the effects of symmetry restoration on nuclear $\beta$ decay within the axially deformed proton-neutron quasiparticle random-phase approximation (QRPA). We employ the proton-neutron finite-amplitude method (pnFAM) to compute transition amplitudes, and perform angular-momentum projection both after variation and after the QRPA to restore rotational symmetry. Exact projection reduces the calculated $\beta$ decay half-lives from those that use the needle approximation by up to 60%, and even more when taking the effects of projection on the ground-state energy into account.

The time evolution of the Wigner distribution function for a single-particle excitation in a Fermi system was studied within the framework of the diffusion approximation of kinetic theory by numerically solving a nonlinear diffusion equation with constant kinetic coefficients. A method was proposed to separate the dissipative processes into contributions from the relaxation of the single-particle excitation and from the relaxation of the nuclear core, with a distinct relaxation time introduced for each process. The influence of the diffusion and drift coefficients on the characteristic relaxation timescale was analyzed. It was found that the resulting relaxation times exhibit a discrepancy relative to the kinetic coefficient estimates known from previous studies.

We have systematically investigated the spectroscopic properties in even-even ${}^{222-228}\mathrm{Ra}$ by introducing the cluster degrees of freedom within the coupled-channels method, which allows the core ${}^{208}\mathrm{Pb}$ to occupy the octupole $3^{-}$ state (Calc. I), as well as both the octupole $3^{-}$ and quadrupole $2^{+}$ states (Calc. II), along with multipole interactions. Excellent agreement has been achieved between our calculated results and available data on energy spectra, reduced electromagnetic $E\lambda$ transition-matrix elements, and intrinsic electric dipole, quadrupole, and octupole $Q_{\lambda }$ moments, pointing to the existence of strong octupole correlations in this region. The description of parity-doublet bands and electromagnetic-transition properties in both calculations is consistent with each other and with experimental data, which confirms the reliability of the coupled-channels formalism based on the cluster-core configuration in heavy nuclei. The enhanced $E2$ and $E3$ matrix elements in both calculations for ${}^{222-226}\mathrm{Ra}$ suggest that these three nuclei can exhibit static octupole deformation in both positive- and negative-parity bands. On the other hand, the accurate reproduction of the higher negative-parity bandhead and the derived $Q_3$ moments in nucleus ${}^{228}\mathrm{Ra}$ is consistent with the interpretation of this nucleus as a deformed rotor exhibiting dynamic/soft octupole vibrations. We hope that the present work may open new avenues for exploring octupole collectivity and cluster correlations in heavy nuclei.

Recent measurements of $B\left(E2\right)$ values in even-even Te isotopes have revealed a smooth evolution of quadrupole collectivity, with only a slight asymmetry across the middle of the shell. These findings confirm that the only nucleus exhibiting an “anomalous” $B_{4/2}$ ratio ($B_{4/2}⩽1$) in even-even Te isotopes is ${}^{114}\mathrm{Te}$. To further investigate this anomaly, lifetime measurements were carried out in the odd-mass isotope ${}^{115}\mathrm{Te}$ ($N=63$), focusing on the $15/2^{-}$ and $19/2^{-}$ negative-parity levels in the $\nu h_{11/2}$ band, which are the analog states of the $2^{+}$ and $4^{+}$ levels in neighboring even-even nuclei. The extracted $B\left(E2\right)$ values for ${}^{115}\mathrm{Te}$ indicate a “normal” behavior, with a $B_{4/2}$ ratio greater than unity, further restricting the extent of the anomalous region in Te isotopes with $B_{4/2}⩽1$ to the lower mass region with $A⩽114$. The results have been interpreted using multiple theoretical frameworks: the shell model with the realistic pairing plus multipole terms with monopole interaction, large-scale configuration-interaction shell-model calculations, and the interacting boson-fermion model with triaxial deformation. The models give a fair reproduction of the experimental data, but fail to capture the detailed trend in the case of the $B_{4/2}$ values.

In this study, the cumulative yields of 106 fission fragments produced from the thermal-neutron-induced fission of ${}^{235}\mathrm{U}$ were experimentally determined. The measurements were carried out through short and long neutron irradiations of natural ${\mathrm{UO}}_2$ samples at the Egypt Second Research Reactor (ETRR-2), followed by $\gamma$-ray spectroscopy of the resulting radioactive fission products. The measured fission yields were compared with the corresponding data reported in the ENDF/B-VIII.1 and JEFF-3.3 nuclear data libraries. While the measured fission yields exhibit generally good agreement with the evaluated data reported in the ENDF/B-VIII.1 and JEFF-3.3 nuclear data libraries, significant discrepancies were observed for some fission products, even between the two evaluations themselves. Consequently, the assessment and refinement of fission yield data remain an ongoing scientific endeavor, contingent upon continual improvements in atomic, nuclear, and decay data, as well as advancements in experimental measurement techniques and theoretical modeling approaches. The cumulative fission product yields measured in this study can serve as benchmark data for the validation and improvement of fission yield evaluation models.

Studying experimental observables is a key benchmark for validating theoretical models in high energy physics. In this work, we employ the PACIAE 4.0 model to simulate nonsingle diffractive proton-proton ($pp$) collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV, comparing the results with compact muon solenoid (CMS) experimental data on charged-particle pseudorapidity densities and transverse momentum spectra across different pseudorapidity bins, respectively. Our results show good agreement with the CMS data, particularly only using a single set of parameters for all collision energies. This demonstrates that the PACIAE 4.0 model can serve as a reliable tool for systematically studying the physics of NSD $pp$ collisions.

In the multifluid description of heavy-ion collisions, the primary scatterings and particle production are described in terms of interaction between fluids, so called friction. These friction terms can be derived from kinetic theory, but they are not unique. We compare different approaches to derive the friction terms, introduce a new “charge transfer” friction, which allows to move charge to the midrapidity fireball, and implement them in the MUFFIN model. The charge transfer friction is more consistent with the assumption of three fluids clearly separated in momentum space, and allows better comparisons of the experimental data and underlying equation of state. It also leaves room for entropy generation due to dissipation in individual fluids, and we present the first results obtained using viscous multifluid dynamics.

Event-by-event fluctuations in the amplitudes of flow harmonics offer a novel approach to probing the initial-state characteristics in heavy-ion collisions. In this study, we conduct a systematic investigation of correlations among various flow harmonics utilizing multiparticle cumulants in ${}^{96}\mathrm{Ru}+{}^{96}\mathrm{Ru}$ and ${}^{96}\mathrm{Zr}+{}^{96}\mathrm{Zr}$ collisions at $\sqrt{s_{NN}}=200$ GeV within the framework of a multiphase transport model. Correlated nuclear density distributions specific to the isobar systems are incorporated to evaluate the sensitivity of selected observables to variations in nuclear deformation and neutron skin thickness. The analysis reveals that multiparticle azimuthal correlations are responsive to these nuclear structure features, predominantly in the most central collision events. Furthermore, the examined correlations exhibit shallow dependence on the assumed shear viscosity values. These findings provide a quantitative evaluation of the extent to which multiparticle flow observables can discern nuclear structure effects in isobar collisions and offer valuable guidance for future detailed dynamical investigations and experimental measurements.

Mirror-symmetry breaking in $\beta$ decays provides a sensitive probe of weak binding and halo structure in proton-rich nuclei. Motivated by the ongoing debate over a halo in ${}^{22}\mathrm{Al}$, we perform ab initio valence-space in-medium similarity renormalization group (VS-IMSRG) calculations, consistently evolving the Hamiltonian and Gamow-Teller (GT) operators. We compute mirror-energy differences (MEDs), GT transition strengths, the mirror-asymmetry parameter $\delta$, average orbital occupations, and relative proton radii $\delta R_p^2$ for the linked mirror $\beta$ decays ${}^{22}\mathrm{Si}/{}^{22}\mathrm{O}$ $\to$ ${}^{22}\mathrm{Al}/{}^{22}\mathrm{F}$ and ${}^{22}\mathrm{Al}/{}^{22}\mathrm{F}$ $\to$ ${}^{22}\mathrm{Mg}/{}^{22}\mathrm{Ne}$, as well as the benchmark mirror $\beta$ decays ${}^{26}\mathrm{P}/{}^{26}\mathrm{Na}$ $\to$ ${}^{26}\mathrm{Si}/{}^{26}\mathrm{Mg}$. Our VS-IMSRG calculations reproduce key experiments in MEDs, GT strengths, and the mirror-asymmetry parameter $\delta$. Based on MEDs and the mirror-asymmetry parameter $\delta$, our calculations support a halo in the ${}^{26}\mathrm{P}$ ground state and a halolike structure in the ${}^{22}\mathrm{Al}$ $1_1^{+}$ state, whereas the ${}^{22}\mathrm{Al}$ ground state retains good mirror symmetry and does not exhibit a halo. Moreover, we also predict halo features in the ${}^{22}\mathrm{Mg}$ $3_1^{+}$ state. These conclusions are corroborated by the calculated $\delta R_p^2$ values.

We investigate the fission barriers of $\mathrm{\Lambda }$ hypernuclei using the multidimensionally constrained relativistic mean-field model, which incorporates both triaxial and octupole degrees of freedom. The effects of triaxial and octupole deformations on the inner and outer fission barriers of ${}^{240}\mathrm{Pu}$ are examined with different relativistic density functionals. Assuming that the $\mathrm{\Lambda }$ hyperon adiabatically follows the fission dynamics and occupies the lowest single-particle state, we analyze the fission barrier heights of ${}_{\mathrm{\Lambda }}{}^{239}\mathrm{U}$ and ${}_{\mathrm{\Lambda }}{}^{241}\mathrm{Pu}$. Our calculations indicate that the shape of the hypernuclei remains nearly identical to that of their core nucleus. The inner fission barrier of ${}_{\mathrm{\Lambda }}{}^{241}\mathrm{Pu}$ is influenced by triaxial deformation, whereas the outer barrier is affected by both triaxial and octupole deformations. The $\mathrm{\Lambda }$ hyperon increases both the inner and outer fission barrier heights due to the attractive $\mathrm{\Lambda }N$ interaction. With the specific $NN$ interaction DD-ME2, we observe that larger $\mathrm{\Lambda }N$ coupling constants correspond to lower inner and outer fission barrier heights. The $\mathrm{\Lambda }$ hyperon localizes at the nuclear center until the system reaches the fission isomer. After passes the outer barrier, it is attached to the heavy fission fragment. These findings are consistent with earlier Skyrme-Hartree-Fock studies, indicating that the influence of the hyperon on fission follows the same trend regardless of deformation degrees of freedom: even when triaxial deformations are included, the localization and attachment behavior of the $\mathrm{\Lambda }$ particle remain unchanged.

Background: Radon isotopes are important candidates of observing octupole deformation. Octupole vibrational bands have been observed in ${}^{220,224,226}\mathrm{Rn}$ but no octupole deformation has been confirmed experimentally.

Purpose: To investigate whether octupole deformation exists in ${}^{220,222,224,226}\mathrm{Rn}$ and explore the possible octupole minima in the potential energy surfaces (PESs).

Methods: The PESs and ground-state properties are calculated by using the mutidimensionally constrained relativistic mean-field model with different covariant energy density functionals PC-PK1, DD-PC1, and DD-ME2. Pairing correlations are treated in the BCS approach with the separable pairing force of finite range.

Results: The calculations show that the PESs of all these isotopes exhibit softness with respect to octupole distortion and octupole minima appear in the PESs of ${}^{222,224}\mathrm{Rn}$ with the above-mentioned functionals and several sets of pairing parameters used. The energy gain due to octupole deformation is found to be suppressed as the pairing strength increases. As the octupole deformation increases, the neutron pairing energy decreases and the proton pairing energy increases while there is no obvious change in the total pairing energy. Analysis of the single-particle levels indicates that the observed octupole minima in ${}^{222,224}\mathrm{Rn}$ primarily originate from the coupling between neutron orbitals $\nu \left[642\right]3/2$ (from $\nu g_{9/2}$) and $\nu \left[761\right]3/2$ (from $\nu j_{15/2}$) near the Fermi surface.

Conclusion: The ground-state properties and PESs of ${}^{220,222,224,226}\mathrm{Rn}$ are studied and predictions are made that octupole minima exist in ${}^{222,224}\mathrm{Rn}$. The energy gain due to octupole deformation ranges from 0.08 to 0.79 MeV. Whether there is octupole deformation is still awaiting experimental confirmation, e.g., through measurement of the $E3$ transition strength from the ground state to the first octupole $3^{-}$ state and observation of parity doublet bands with enhanced $E1$ transitions between them.

We analyze the chart containing both spontaneous and β-delayed proton emission processes in terms of the Coulomb parameter, reduced radius, and angular momentum ($\chi , \rho , l$). We then compare the methods to estimate the decay width $\mathrm{\Gamma }$ of a resonant state in a proton mean field, namely, the continuity equation for outgoing Gamow states, phase shift analysis of real scattering states, and numerical integration of the Schrödinger equation in the complex plane. We show that they provide similar results in the region where it is possible to evaluate the imaginary part of the energy for a resonant (Gamow) state. We then investigate the role of the centrifugal barrier induced by Coulomb interaction and also by proton single-particle orbitals. We show that the so-called universal decay law, connecting the logarithm of the monopole reduced width to the fragmentation potential, remains also valid for β-delayed proton emission processes. This fact allows us to describe experimental data for all proton emission processes in terms of a linear dependence connecting the logarithm of the monopole Coulomb-reduced decay width to the logarithm of the monopole Coulomb penetrability and fragmentation potential within a factor of 3 for absolute values.

Low-energy quadrupole collective states in even-even tellurium (Te) isotopes are studied using the interacting boson model with configuration mixing. The corresponding Hamiltonian is determined by means of the microscopic nuclear structure calculations within the self-consistent mean-field method employing a given energy density functional and pairing interaction. Calculated low-energy levels for nonyrast states show a parabolic behavior characteristic of the shape-coexisting structure. The intruder prolate-shape configuration is shown to mix strongly with the normal oblate-shape configuration and play an important role in determining the low-lying structure in the Te isotopes near the middle of the neutron major shell closures.

We investigate the use of normalizing flow (NF) models as flexible priors in Bayesian inference via Markov chain Monte Carlo (MCMC) sampling for iterative Bayesian calibration. Trained on posteriors from previous analyses, these models can be used as informative priors that capture nontrivial distributions and correlations in subsequent inference tasks. We compare different training strategies and loss functions, finding that training based on Kullback-Leibler divergence and unsupervised learning consistently yield the most accurate reproductions of reference distributions. We apply such a sequential Bayesian workflow to a high-energy nuclear physics problem; MCMC with NF-based priors reproduces the results of one-shot joint inference well, provided the target distributions are unimodal. In cases with pronounced multi-modality or dataset tension, distortions may arise, underscoring the need for caution in multi-stage Bayesian inference. A comparison between the pocoMC MCMC sampler and the standard emcee sampler further demonstrates the importance of advanced and robust algorithms for exploring the posterior space. Overall, our results establish NF-based priors as a practical and efficient tool for sequential Bayesian inference in high-dimensional parameter spaces.

The Richardson-Lucy algorithm is applied to reconstruct the three-dimensional source function of identical pions from their two-particle correlation functions. The algorithm's performance is first evaluated through simulations with Gaussian-type initial source functions. Its imaging quality and robustness are further demonstrated with experimental ${\pi }^{-}\text{−}{\pi }^{-}$ correlation functions from $\mathrm{Au}+\mathrm{Au}$ collisions at $1.23A$ GeV, collected by the HADES Collaboration. Additionally, using UrQMD simulations of $\mathrm{Pb}+\mathrm{Pb}$ collisions at $1.5A$ GeV, we show that the deblurred source functions from ${\pi }^{-}\text{−}{\pi }^{-}$ correlation exhibit sensitivity to the initial neutron skin thickness of the colliding nuclei. This highlights the potential applicability of the Richardson-Lucy algorithm as a tool for probing the neutron density distribution in heavy nuclei.

Muon-catalyzed fusion has recently regained significant attention due to experimental and theoretical developments. The present authors proposed Q. Wu and M. Kamimura, [Phys. Rev. C 109, 054625 (2024)] the tractable $T$-matrix model based on the Lippmann-Schwinger equation to approximate the elaborate two- and three-body coupled-channel (CC) calculations M. Kamimura, Y. Kino, and T. Yamashita, [Phys. Rev. C 107, 034607 (2023)] for the nuclear reaction processes in the muonic molecule $dt\mu , {\left(dt\mu \right)}_{J=0}{\to }^4\mathrm{He}+n+\mu +17.6\mathrm{MeV}$. The $T$-matrix model well reproduced almost all of the results generated by the CC work. In the present paper, we apply this model to the nuclear reaction processes in the $dd\mu$ molecule, ${\left(dd\mu \right)}_{J=1}{\to }^3\mathrm{He}+n+\mu +3.27$ MeV or $t+p+\mu +4.03$ MeV, in which the fusion takes place via the $p$-wave $d\text{−}d$ relative motion. Recently, significantly different $p$-wave astrophysical $S\left(E\right)$ factors of the reaction $d+d{\to }^3\mathrm{He}+n$ or $t+p$ at $E\simeq 1$ keV to 1 MeV have been reported experimentally and theoretically by five groups. Employing many sets of nuclear interactions that can reproduce those five cases of $p$-wave $S\left(E\right)$ factors, we calculate the fusion rate of the ${\left(dd\mu \right)}_{J=1}$ molecule using three kinds of methods where results are consistent with each other. We also derive the ${}^3\mathrm{He}\text{−}\mu$ sticking probability and the absolute values of the energy and momentum spectra of the emitted muon. The violation of charge symmetry in the $p$-wave $d\text{−}d$ reaction and the $dd\mu$ fusion reaction is discussed. Information on the emitted 2.45 MeV neutrons and 1 keV dominant muons should be useful for the application of $dd\mu$ fusion.