A neutron-generator-based source of fission products (nuCARIBU) is being developed to replace the existing ${}^{252}\mathrm{Cf}$ source at Argonne National Laboratory. Neutrons generated by ${}^7\mathrm{Li}(p,n){}^7\mathrm{Be}$ reaction are thermalized in a compact polyethylene [(${\mathrm{C}}_2{\mathrm{H}}_4{)}_n]$ moderator and impinge on a thin ${}^{235}\mathrm{U}$ foil to produce fission products. Experiments have been conducted to verify the nuCARIBU concept and simulation results using a 4 MeV, $0.16\mu \mathrm{A}$ proton beam from the ATLAS accelerator irradiating a LiF neutron production target and two different simplified versions of the nuCARIBU (${\mathrm{C}}_2{\mathrm{H}}_4{)}_n$ moderator with thicknesses of 3.81 cm and 1.91 cm separating it from the enriched ${}^{235}\mathrm{U}$ fission foil. The emitted $\gamma$-ray peaks of 1383.93 keV (${}^{92}\mathrm{Sr}$), 358.0 keV (${}^{104}\mathrm{Tc}$), 565.992 keV (${}^{134}\mathrm{Te}$), and 258.411 keV (${}^{138}\mathrm{Xe}$) obtained from fission products are used to determine the neutron-induced fission rates in the fission foil. The measured fission rates are in good agreement with those simulated using the PHITS Monte Carlo code with user-defined neutron production cross sections based on well-known cross section data. These experimental results, consistent with the simulations, show that the current ${}^{252}\mathrm{Cf}$ source (CARIBU) can be replaced by the neutron induced fission source (nuCARIBU).

We study diffractive vector meson production in ultraperipheral collisions of heavy nuclei, utilizing a theoretical framework based on the color glass condensate formalism. We focus on $\mathrm{Au}+\mathrm{Au}, \mathrm{U}+\mathrm{U}, \mathrm{Ru}+\mathrm{Ru}, \mathrm{Zr}+\mathrm{Zr}$, and $\mathrm{Pb}+\mathrm{Pb}$ collisions, examining the transverse momentum dependence of vector meson production cross-sections and $\cos \left(2\mathrm{\Delta }\mathrm{\Phi }\right)$ asymmetries in the decay product distributions to explore the role of nuclear geometry. The angular modulation is due to the linear polarization of the incoming photons and quantum interference effects. We extract nuclear radii and find them to be consistent with experimental data from the STAR collaboration. The amplitudes of the $\cos \left(2\mathrm{\Delta }\mathrm{\Phi }\right)$ modulation in the cross-section and the extracted radii depend on the nuclear geometry. This dependence is dominated by the geometry-dependent variation of the minimum impact parameter required for ultraperipheral collisions.

We present updated and extended results for the $\eta$- and ${\eta }^{\prime }$-nucleus bound state energies, obtained by solving the Schrödinger and Klein-Gordon equations with complex optical potentials, for a wide range of nuclei. The $\eta$ and ${\eta }^{\prime }$ nuclear potentials are obtained in the local density approximation from the mass shift of these mesons in nuclear matter, which is calculated within the quark-meson coupling model. Our results show that the $\eta$ and ${\eta }^{\prime }$ mesons are expected to form mesic nuclei with all the nuclei considered. However, the signal for the formation of the $\eta$- and ${\eta }^{\prime }$-mesic nuclei may be difficult to identify experimentally due to possible large widths.

The quasiparticle model is improved by the free magnetic contribution to investigate the QCD matter in a strong magnetic field. The temperature-dependent bag function is determined by the thermodynamic consistency to represent the difference in energy density between physical vacuum and the lowest state of QCD. It is found that the positive bag function vanishes at high temperature, indicating the deconfinement. The rapid decrease of the bag function in stronger magnetic fields reveals the so-called inverse magnetic catalysis. The interaction measure at high temperature remains so large that the usual Stefan-Boltzmann limit cannot be reached. We suggest a limit $|q_i{B}_m|T^2/4$ for each Landau level pressure. Finally, it is demonstrated that the positive magnetization modified by the bag function and free magnetic contribution indicates the paramagnetic characteristic of QCD matter.

Electron emission in the deuteron-deuteron reaction supporting existence of the single-particle threshold resonance in ${}^4\mathrm{He}$ has been observed for the first time. The measured electron energy spectrum and the electron-proton branching ratio agree very well with the assumed electron-positron pair creation decay of the $0^{+}$ resonance state to the ground state and the detailed Monte Carlo simulations of the experimental energy spectrum.

The $g$ factor of chiral doublet bands has been extensively studied within the framework of the particle rotor model. Specifically, these investigations have focused on systems characterized by the particle-hole configuration $\pi {\left(1h_{11/2}\right)}^1\otimes \nu {\left(1h_{11/2}\right)}^{-1}$. Comprehensive examinations have been carried out to assess the influence of deformation parameters $\beta$ and $\gamma$, the moment of inertia ${\mathcal{J}}_0$, the total spin $I$, and the angular momentum of the collective rotor $j_R$ on the $g$ factor. The findings reveal that the $g$ factor exhibits insensitivity to variations in ${\mathcal{J}}_0$ and $\beta$ values, while its behavior is highly sensitive to changes in the $\gamma$ parameter. Moreover, it has been observed that the $g$ factors and the $g\left(j_R\right)$ plots associated with the doublet bands demonstrate remarkable similarity in the static chirality region. However, noticeable differences arise in regions characterized by chiral vibration or lacking chirality.

Excited structures in ${}^{146}\mathrm{Ce}$ were populated in $\beta$ decay of the high-spin state in the neutron-rich nucleus ${}^{146}\mathrm{La}$. The beam was produced by the Californium Rare Isotope Breeder Upgrade (CARIBU) facility at Argonne National Laboratory, reaccelerated by the ATLAS accelerator, and implanted on a moving-tape system in the middle of the GAMMASPHERE array. The decay scheme of the high-spin, $\beta$-decaying state in ${}^{146}\mathrm{La}$ was revised with respect to previous studies and evaluated nuclear data. The structure of ${}^{146}\mathrm{La}$ is discussed in the framework of the deformed Nilsson model and systematics of known quasiparticle structures in the region.

Background: Nuclear masses are of fundamental importance in both nuclear physics and astrophysics, and the masses for most neutron-rich exotic nuclei are still beyond the experimental capability. The relativistic continuum Hartree-Bogoliubov (RCHB) theory has achieved great successes in the studies of both stable and exotic nuclei. The mass table based on the RCHB theory has been constructed with the assumption of spherical symmetry [Xia et al., At. Data Nucl. Data Tables 121, 1 (2018)]. The upgraded version including deformation effects based on the deformed relativistic Hartree-Bogoliubov theory in continuum (DRHBc) is under construction, and the part for even-even nuclei has been finished [Zhang et al., At. Data Nucl. Data Tables 144, 101488 (2022)]. The kernel ridge regression (KRR) approach is a useful machine-learning approach in refining nuclear mass prediction, and is found to be reliable in avoiding the risk of worsening predictions at large extrapolation distance [Wu and Zhao, Phys. Rev. C 101, 051301(R) (2020)].

Purpose: The aim of this work is to combine the RCHB mass model and the KRR approach to construct a high-precision and reliable nuclear mass model describing both stable and weakly bound neutron-rich exotic nuclei. Another purpose is to utilize the masses of even-even nuclei from the DRHBc theory to validate the performance of the KRR approach.

Method: The KRR approach is employed to refine the RCHB mass model by learning and representing the mass residual of the RCHB mass model with the experimental data. The leave-one-out cross-validation is applied to determine the hyperparameters in the KRR approach. The DRHBc mass model for even-even nuclei is employed to help to analyze the physical effects included in the KRR corrections and examine the KRR extrapolations.

Results: The refined RCHB mass model with KRR corrections can achieve an accuracy of root-mean-square deviation 385 keV from the experimental masses. The major contributions contained in the KRR corrections are found to be the deformation effects. The KRR corrections also contain some residual deformation effects and some other effects beyond the scope of the DRHBc theory. The extrapolation of the KRR approach in refining the RCHB predictions is found to be very reliable.

Conclusions: A mass model benefiting from the RCHB model with continuum effects properly treated and the KRR approach is constructed. This model is demonstrated to be accurate in reproducing the masses of experimentally known nuclei and reliable in extrapolating to the experimentally unknown neutron-rich regions.

We investigated the elastic scattering, inelastic scattering, breakup reactions, and total fusion reactions of the ${}^{17}\mathrm{Ne}+{}^{208}\mathrm{Pb}$ system using the extended optical model (OM) and a coupled channel (CC) approach. The aim of this study is to elucidate the suppression of the elastic cross section that is invisible in proton-rich nuclei, such as ${}^8\mathrm{B}$ and ${}^{17}\mathrm{F}$ projectiles, but appears in neutron-rich nuclei, such as ${}^{11}\mathrm{Li}$ and ${}^{11}\mathrm{Be}$ projectiles. The simultaneous ${\chi }^2$ analysis of the ${}^{17}\mathrm{Ne}+{}^{208}\mathrm{Pb}$ system revealed that this suppression was primarily caused by the nuclear interaction between the projectile and the target nucleus, rather than the strong Coulomb interaction observed in neutron-rich nuclei. Moreover, the contributions of the Coulomb excitation interaction due to the two low-lying $E2$ resonance states were relatively small. In addition, the contribution of the direct reaction, comprising the inelastic scattering and breakup reaction cross sections, accounted for almost half of the total reaction cross section. Finally, we performed the CC calculation using the parameters obtained from the OM calculation; however, the present CC calculations could not properly explain the ${}^{15}\mathrm{O}$ production cross section.

In this work, the Light Gradient Boosting Machine (LightGBM), which is a modern decision tree based machine-learning algorithm, is used to study the fusion cross section (CS) of heavy-ion reaction. Several basic quantities (e.g., mass number and proton number of projectile and target) and the CS obtained from phenomenological formula are fed into the LightGBM algorithm to predict the CS. It is found that, on the validation set, the mean absolute error (MAE) which measures the average magnitude of the absolute difference between ${log}_{10}$ of the predicted CS and experimental CS is 0.129 by only using the basic quantities as the input, this value is smaller than 0.154 obtained from the empirical coupled channel model. MAE can be further reduced to 0.08 by including an physical-informed input feature. The MAE on the test set (it consists of 280 data points from 18 reaction systems that not included in the training set) is about 0.19 and 0.53 by including and excluding the physical-informed feature, respectively. We further verify the LightGBM predictions by comparing the CS of ${}^{40,48}\mathrm{Ca}+{}^{78}\mathrm{Ni}$ obtained from the density-constrained time-dependent Hartree-Fock approach. Our study demonstrates the importance of physical information in predicting fusion cross section of heavy-ion reaction with machine learning.

A general method is proposed to obtain the distribution of the total quantum number $M$ for a set of $N$ identical fermions with momentum $j$, which is a cornerstone of the nuclear shell model. This can be performed using a recursive procedure on $N$, yielding closed-form expressions, which are found to be linear combinations of piecewise polynomials. We also highlight and implement in that framework two three-term recurrence relations over $N$, more convenient than Talmi's five-term recurrence which has nevertheless already proved its worth in the past. In addition, the current approach allows one to consider both integer and half-integer values of $j$ on the same footing. The technique is illustrated by detailed examples, corresponding to $N=3$ to 6 fermions.

A pair of new possible chiral doublet bands has been experimentally identified for the first time in the odd-odd nucleus ${}^{126}\mathrm{Cs}$. The possibility of multiple chiral doublet $\left(\mathrm{M}\chi \mathrm{D}\right)$ bands in ${}^{126}\mathrm{Cs}$ was interpreted by projected shell model (PSM) calculations with a relatively complete configuration space. The newly observed bands and the first chiral doublet band reported earlier belong to an identical configuration, providing the first experimental and theoretical evidence for the existence of multiple chiral doublet bands of odd-odd nuclei in the $A\approx 130$ mass region.

A multiphase transport model (AMPT) is employed to predict symmetric correlations (SC), asymmetric correlations (ASC), normalized symmetric correlations (NSC), and normalized asymmetric correlations (NASC) in ${}^{96}\mathrm{Ru}+{}^{96}\mathrm{Ru}$ and ${}^{96}\mathrm{Zr}+{}^{96}\mathrm{Zr}$ collisions at 200 GeV. This study offers insights into the behavior of SC, ASC, NSC, and NASC, considering various nuclear structure scenarios to account for differences between the two isobars. Additionally, I emphasize the importance of detailed experimental measurements as they will serve as a critical constraint for refining the predictions of theoretical models.

The static quadrupole moments (SQMs) of multiple chiral doublet bands are investigated. An interesting finding for the SQM is the occurrence of a kink at specific spin values for various $\gamma$ values. The kink represents the transition point from planar to chiral rotation. This observation highlights a robust feature that the presence of a kink in the SQM plot serves as compelling evidence for the initiation of aplanar rotation. Thus, the SQMs presents a novel criterion for effectively distinguishing different modes of nuclear chirality.

Over the last decade, conflicting values of the hypertriton ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ lifetime $\tau \left({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\right)$ were extracted from relativistic heavy-ion (RHI) collision experiments, ranging from values compatible with the free-$\mathrm{\Lambda }$ lifetime ${\tau }_{\mathrm{\Lambda }}$—as expected naively for a very weakly bound $\mathrm{\Lambda }$ in ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$—to lifetimes as short as $\tau \left({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\right)\approx \left(0.4\text{–}0.7\right){\tau }_{\mathrm{\Lambda }}$. In a recent work [Phys. Lett. B 811, 135916 (2020)] we studied this ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ lifetime puzzle theoretically using realistic three-body ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and ${}^3\mathrm{He}$ wave functions computed within the ab initio no-core shell model approach with interactions derived from chiral effective field theory to calculate the partial decay rate $\mathrm{\Gamma }({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\to {}^3\mathrm{He}+{\pi }^{-})$. Significant but opposing contributions were found from $\mathrm{\Sigma }NN$ admixtures in ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$ and from ${\pi }^{-}\text{−}{}^3\mathrm{He}$ final-state interaction. In particular, $\tau \left({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\right)$ was found to be strongly correlated with the $\mathrm{\Lambda }$ separation energy $B_{\mathrm{\Lambda }}$ in ${}_{\mathrm{\Lambda }}{}^3\mathrm{H}$, the value of which is rather poorly known experimentally and, in addition, is known to suffer from sizable theoretical uncertainties inherent in the employed nuclear and hypernuclear interaction models. In the present work we find that these uncertainties propagate into $\tau \left({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\right)$, and thus limit considerably the theoretical precision of its computed value. Although none of the conflicting RHI measured $\tau \left({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\right)$ values can be excluded, but rather can be attributed to a poor knowledge of $B_{\mathrm{\Lambda }}$, we note the good agreement between the lifetime value $\tau \left({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\right)=242\left(28\right)\mathrm{ps}$ computed at the lowest value $B_{\mathrm{\Lambda }}=66\mathrm{keV}$ reached by us and the very recent ALICE measured lifetime value ${\tau }^{\text{ALICE}}\left({}_{\mathrm{\Lambda }}{}^3\mathrm{H}\right)=253\left(11\right)\left(6\right)\mathrm{ps}$ associated with the ALICE measured $B_{\mathrm{\Lambda }}$ value $B_{\mathrm{\Lambda }}^{\text{ALICE}}=102\left(63\right)\left(67\right)\mathrm{keV}$ [S. Acharya et al. (ALICE Collaboration), Phys. Rev. Lett. 131, 102302 (2023)].

The effects of shape coexistence on first-forbidden ${\beta }^{-}$ decay of the $0^{-}$ ground state of ${}^{92}\mathrm{Rb}$ to the $0^{+}$ ground state and $2^{+}$ states in ${}^{92}\mathrm{Sr}$ were studied within the beyond-mean-field complex excited Vampir variational model. The structure of the parent and daughter states and the $\beta$-decay properties were investigated using an effective interaction derived from a $G$ matrix based on the charge-dependent Bonn CD potential and a large model space. The effects of shape coexistence and mixing revealed by the structure of the involved states on the properties of the investigated ground state to ground state and first-forbidden unique transitions are discussed and comparison to the available data is presented.

Lifetimes of the $15/2_1^{-}$ and 13/$2_1^{-}$ levels in ${}^{129}\mathrm{Sn}$ have been measured using $\gamma \text{−}\gamma$ fast timing technique which come out to be 10(3) ps and 6(4) ps, respectively. The excited states were populated through internal transition decay of higher lying $\mu \mathrm{s}$ isomers in ${}^{129}\mathrm{Sn}$ produced as fission fragments and mass separated by the Lohengrin separator at Institut Laue-Langevin. The generalized centroid difference method was applied with four ${\mathrm{LaBr}}_3$(Ce) detectors, placed at the focal plane of the separator. The measured lifetimes and absolute transition probabilities are discussed in the light of large scale shell model calculations to interpret the single particle configurations and their mixing.

Finite-temperature effects in electromagnetic transitions in nuclei contribute to many aspects of nuclear structure and astrophysically relevant nuclear reactions. While electric dipole transitions have already been extensively studied, the temperature sensitivity of magnetic transitions remains largely unknown. This work comprises the study of isovector magnetic dipole excitations ($M1$) occurring between spin-orbit (SO) partner states using the recently developed self-consistent finite-temperature relativistic quasiparticle random-phase approximation (FT-RQRPA) in the temperature range from $T=$ 0 to 2 MeV. The $M1$ strength distributions of ${}^{40-60}\mathrm{Ca}$ and ${}^{100-140}\mathrm{Sn}$ isotopic chains exhibit a considerable temperature dependence. The $M1$ strength peaks shift significantly towards the lower energies due to the decrease in SO splitting energies and weakening of the residual interaction, especially above the critical temperatures where the pairing correlations vanish. By exploring the relevant two-quasiparticle configurations contributing to the $M1$ strength of closed- and open-shell nuclei, new proton and neutron excitation channels between SO partners are observed in low- and high-energy regions due to the thermal unblocking effects around the Fermi level. At higher temperatures, we have noticed an interesting result in ${}^{40,60}\mathrm{Ca}$ nuclei, the appearance of $M1$ excitations, which are forbidden at zero temperature due to fully occupied (or fully vacant) spin-orbit partner states.

A system of gluon fields produced in the earliest phase of relativistic heavy-ion collisions, which is called glasma, can be described in terms of classical fields. Initially there are chromoelectric and chromomagnetic fields along the collision axis. A linear stability analysis of these fields is performed, assuming that the fields are space-time uniform and using the SU(2) gauge group. We apply Milne coordinates and the gauge condition, which are usually used in studies of glasma. The chromoelectric field is in the Abelian configuration with the corresponding potential linearly depending on coordinates, but the chromomagnetic field is in the non-Abelian configuration generated by the potential of noncommuting components. The chromomagnetic field is found to be unstable, and the growth rate of the unstable mode is derived. Our findings are critically debated and confronted with the numerical simulations by Romatschke and Venugopalan, who found that the evolving glasma is unstable due to the Weibel instability, which is well known in electromagnetic plasma.

The ratio of shear viscosity to entropy density shows a valley-shaped pattern well-known in the community of heavy-ion physics. Diffusion coefficients of heavy quark and meson show a similar structure, and both sketches have become quite popular in the community. Present work has attempted a finite magnetic field extension of the diffusion coefficients of heavy quark and meson. Using Einstein's diffusion relation, we calculated heavy quark and heavy meson diffusion by the ratio of conductivity to susceptibility in the kinetic theory framework of relaxation time approximation. The relaxation time of heavy quark and meson are tuned from the knowledge of earlier works on spatial diffusion estimations, and then we have extended the framework for a finite magnetic field, where our outcomes have revealed two aspects—anisotropic and quantum aspects of diffusion with future possibilities of phenomenological signature.