A microscopic description of nuclear fission represents one of the most challenging problems in nuclear theory. While phenomenological coordinates, such as multipole moments, have often been employed to describe fission, it is not obvious whether these parameters fully reflect the shape dynamics of interest. We here propose a novel method to extract collective coordinates, which are free from phenomenology, based on multitask deep learning in conjunction with density functional theory (DFT). To this end, we first introduce randomly generated external fields to a Skyrme energy density functional (EDF) and construct a set of nuclear number densities and binding energies for deformed states of ${}^{236}\mathrm{U}$ around the ground state. By training a neural network on such a dataset with a combination of an autoencoder and supervised learning, we successfully identify a two-dimensional latent variables that accurately reproduce both the energies and the densities of the original Skyrme-EDF calculations, within a mean absolute error of 113 keV for the energies. In contrast, when multipole moments are used as latent variables for training in constructing the decoders, we find that the training data for the binding energies are reproduced only within 2 MeV. This implies that conventional multipole moments do not provide fully adequate variables for a shape dynamics of heavy nuclei.

The fusion-evaporation reaction ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$ aimed at synthesizing new neutron-deficient protactinium isotopes has been studied at the gas-filled recoil separators SHANS and SHANS2. The cross sections for the $xn$ and $pxn$ evaporation channels were measured. The calculation by the statistical model HIVAP was performed to reproduce the experimental data. The quasifission process in the ${}^{40}\mathrm{Ca}+{}^{175}\mathrm{Lu}$ reaction was also studied with time-dependent Hartree-Fock theory and the improved quantum molecular dynamics model. It is shown that the influence of quasifission in the analysis of evaporation residue cross sections of this reaction can be neglected.

A global phenomenological energy dependent optical potential for the radioactive nucleus ${}^7\mathrm{Be}$ on various targets is developed. This optical potential is based on Woods-Saxon form factors with a smooth mass dependent potential depth for above-barrier energies and an energy and mass dependent depth below barrier. The potential is validated with elastic scattering and fusion calculations which are compared with experimental data and are found to be in very good agreement. The present potential is compared with the energy dependent Cook potential, developed for ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$.

We present a method for the global analysis of elastic electron-proton scattering when combining data sets from experiments with different overall normalization uncertainties. The method is a modification of one employed by the NNPDF collaboration in the fitting of parton distribution data. This method is an alternative to the ‘penalty trick’ method traditionally employed in global fits to proton electric and magnetic form factors, while avoiding the statistical biases inherent in that approach. We discuss issues that arise when extending the method to nonlinear models. For data with $Q^2>1{\text{GeV}}^2$ we find relatively minor differences to traditional model fits when the normalization uncertainties from different experiments are correctly accounted for. We discuss implications of this method for the well-known discrepancy between the form factor ratio $G_E/G_M$ extracted from the Rosenbluth and polarization transfer techniques.

Fusion enhancement for neutron-rich isotopes of oxygen on carbon nuclei was probed. To measure the fusion cross section a ${}^{20}\mathrm{O}$ beam accelerated to $E_{\mathrm{lab}}/A=2.7$ MeV bombarded the active-target detector MuSIC@Indiana with a fill gas of ${\mathrm{CH}}_4$. Examination of the average fusion cross section over the interval $0.5\le (E_{\mathrm{c}.\mathrm{m}.}-V_B)/V_B\le 1.2$ for ${}^{16–20}\mathrm{O}+{}^{12}\mathrm{C}$ reveals that while even isotopes of oxygen exhibit essentially the same cross section, the cross section for odd isotopes can be either enhanced or suppressed relative to the even $A$ members of the isotopic chain. Theoretical models fail to explain the observed experimental results.

Background: Several approaches are currently trying to understand the generation of angular momentum in the fission fragments. The microscopic TDDFT and statistical FREYA lead to different predictions concerning the opening angle distribution formed between the two spins in particular at 0 and 180 degrees.

Purpose: This Letter aims to investigate how the geometry and the quantum nature of spins impact the distribution of opening angles to understand what leads to different model predictions.

Method: Various assumptions of $K$ distribution ($K=0$, isotropic, isotropic with total $K=0$, and from TDFFT) are investigated in a quantum approach. These distributions are then compared to the classical limit using the Clebsch-Gordan coefficients in the limit of $\hslash$ approaches zero.

Results: It is shown that in all the schematic scenario the quantal distribution of opening angle lead to the expected behavior in the classical limit. The model shows that the quantal nature of the spins prevents the population of opening angles close to 0 and 180 degrees. The difference in opening angle in the two-dimensional and isotropic three-dimensional distribution is discussed and it is shown that the realistic TDFFT opening angle distribution presents an intermediate behavior between the two cases.

Conclusions: The last comparison reveals two key differences between the two model's predictions: the quantal spins' nature in TDDFT and the assumption of zero $K$ values in FREYA.

The cross-shell excited states of ${}^{34}\mathrm{Si}$ have been investigated via $\beta$ decays of the $4^{-}$ ground state and the $1^{+}$ isomeric state of ${}^{34}\mathrm{Al}$. Since the valence protons and valence neutrons occupy different major shells in the ground state as well as the intruder $1^{+}$ isomeric state of ${}^{34}\mathrm{Al}$, intruder levels of ${}^{34}\mathrm{Si}$ are populated via allowed $\beta$ decays. Spin assignments to such intruder levels of ${}^{34}\mathrm{Si}$ were established through $\gamma \text{−}\gamma$ angular correlation analysis for the negative-parity states with dominant configurations ${\left(\nu d_{3/2}\right)}^{-1}\otimes {\left(\nu f_{7/2}\right)}^1$ as well as the positive-parity states with dominant configurations ${\left(\nu sd\right)}^{-2}\otimes {\left(\nu f_{7/2}{p}_{3/2}\right)}^2$. The configurations of such intruder states play crucial roles in our understanding of the $N=20$ shell gap evolution. A configuration interaction model derived from the FSU Hamiltonian was utilized in order to interpret the intruder states in ${}^{34}\mathrm{Si}$. Shell model interaction derived from a more fundamental theory with the valence space in medium similarity renormalization group method was also employed to interpret the structure of ${}^{34}\mathrm{Si}$.

Systematic shell-model calculations are presented for odd-mass Cd isotopes with $N=51\text{−}81$ utilizing a combination of a $G$-matrix interaction and a semiempirical one. The excited energy spectra and electromagnetic transition probabilities are compared with the recently available experimental data. We have found that the observed quadrupole moments in the $11/2_1^{-}$ states that linearly change with the neutron number are well accounted for by the dominance of prolate shapes throughout the Cd isotope chain. We have also described the properties of several isomeric states in neutron-rich ${}^{127–131}\mathrm{In}$ isotopes that were recently observed in Jyväskylä.

Covariant density functional theory is solved in 3D lattice space by implementing the preconditioned conjugate gradient method with a filtering function. It considerably improves the computational efficiency compared to the previous inverse Hamiltonian method (IHM). This new method is then applied to explore the tetrahedral shape of ${}^{110}\mathrm{Zr}$ in the full deformation space. Although the ground-state energy and deformation are consistent with the previous study, the pear-shaped isomeric state is significantly lowered in energy. The energy difference between the two states is only 0.07 MeV, indicating an interesting possible shape coexistence in ${}^{110}\mathrm{Zr}$. This effect is analyzed with the microscopic evolution of the single-particle levels near the Fermi surface driven by the deformation.

We systematically investigate the $\alpha$-decay and spontaneous fission (SF) half-lives of superheavy nuclei (SHN) $Z=124$ and 126 in the mass number range $292\le A\le 314$. The $\alpha$-decay half-lives $\left({log}_{10}{T}_{1/2}\right)$ have been calculated within the double folding model (DFM), the universal decay law (UDL), the scaling law of Horoi, and the universal curve (UNIV) formula. To identify the mode of decay of these SHN, a competition between SF half-lives and $\alpha$-decay half-lives has been performed. The study reveals that even-mass number isotopes of ${}^{292\text{–}314}124$ and ${}^{292\text{–}314}126$ will survive fission, and $\alpha$ chains can also be predicted from these SHN. The variation of ${log}_{10}{T}_{1/2}$ against parent nucleus mass numbers of $\alpha$-decay chains of each SHN isotope is found to be governed by the presence of magic or semimagic nucleon numbers of the parent nucleus in the sense that ${log}_{10}{T}_{1/2}$ becomes maximum at or near these numbers. The probable heavy cluster radioactivity (CR) in the mass number range $A_c=18\text{–}126$ from ${}^{294\text{–}324}124$ and ${}^{294\text{–}312}126$ is also studied using the same four models of $\alpha$-decay half-lives. Heavy clusters with charge numbers in the range $36\le Z_c\le 46$ are dominant decay modes relative to $\alpha$ decay. Clusters with small $log{T}_c$ values relative to $\alpha$ decay are found to be the six clusters, $\mathrm{Kr}$, $\mathrm{Sr}$, $\mathrm{Zr}$, $\mathrm{Mo}$, $\mathrm{Ru}$, and Pd. The most probable cluster emissions having the smallest $log{T}_c$ values relative to $\alpha$ decay are ${}^{104\text{–}106}\mathrm{Mo}$ and ${}^{106\text{–}110}\mathrm{Ru}$ from ${}^{312}124$; from ${}^{296}126$ the clusters are ${}^{94\text{–}96}\mathrm{Mo},{}^{104\text{–}106}\mathrm{Pd}$; from ${}^{298}126$ the clusters are ${}^{90}\mathrm{Zr}$, ${}^{96}\mathrm{Mo}$; and from the SHN isotope ${}^{300}126$ the most probable clusters are ${}^{100\text{–}102}\mathrm{Ru}$. We found that the most probable cluster emissions occur when the proton and neutron numbers in the emitted clusters and their residual daughter nuclei are magic or near to the magic numbers.

The statistical model for the calculation of the compound nucleus formation cross section and the probability of compound nucleus formation in heavy-ion collisions is discussed in detail. Light, heavy, and superheavy nucleus-nucleus systems are considered in this model in the framework of one approach. It is shown that the compound nucleus is formed in competition between passing through the compound-nucleus formation barrier and the quasielastic barrier. The compound-nucleus formation barrier is the barrier separating the system of contacting incident nuclei and the spherical or nearly spherical compound nucleus. The quasielastic barrier is the barrier between the contacting and well-separated deformed ions, which are the same as the incident ions. It is shown that the compound nucleus formation cross section is suppressed when the quasielastic barrier is lower than the compound nucleus formation barrier. The critical value of angular momentum, which limits the compound nucleus formation cross-section values for light and medium-mass ion-ion systems at above-barrier collision energies, is discussed in the model. The suppression of the compound nucleus formation cross section even at small partial waves for very heavy ion-ion systems is obtained in the model. The values of the capture and compound nucleus formation cross sections calculated for various light, heavy, and superheavy nucleus-nucleus systems as well as the probability of the compound nucleus formation for superheavy nuclei agree well with the available experimental data.

Kinetic and chemical equilibrations play important roles in the formation of the quark-gluon plasma (QGP) in relativistic heavy-ion collisions (HICs). These processes further influence the production of hard and electromagnetic probes in HICs, in particular, the thermalization of heavy quarks, which are produced at an extremely early time before the formation of the QGP. I calculate the drag and diffusion coefficients of heavy quarks in the prehydrodynamic quantum chromodynamic (QCD) plasma with the state-of-the-art QCD effective kinetic theory (EKT) solver. The time, momentum, and angular dependencies of these coefficients for gluon and quark contributions are presented separately, showing the effects of isotropization and chemical equilibration from the QCD plasma. I also provide a simple formula to estimate the heavy quark drag and diffusion coefficients, as well as its energy loss, within the prehydrodynamic plasma at different coupling strengths based on the attractor theory. Finally, I discuss the validity of these estimations with leading-order calculations and leading-logarithmic rescaling factors.

Isospin asymmetric quark matter is investigated with the Polyakov Nambu–Jona-Lasinio model at zero temperature in a strong magnetic field. The isospin symmetry/asymmetry can be controlled by altering the fraction parameter $\alpha$ of the two kinds of interactions, i.e., the scalar coupling and instanton-induced coupling. Specially, the flavor decoupled state with $\alpha =0$ is strongly isospin asymmetric. It is accompanied by the discrepancy of the $u$ and $d$ quarks in the chiral phase transitions, which is eliminated up to $\alpha =0.5$. It is found that there exists a critical value ${\alpha }_c$, above which the simultaneous chiral restoration would happen for the flavor isodoublet, no matter whether their masses are equal or not. The ${\alpha }_c$ can be decreased by the increase of the magnetic field. Finally, it is suggested that the presence of the Polyakov potential increases the maximum central magnetic field of compact stars up to $3.5\times {10}^{18}$ G.

This paper delves into the distribution of semi-inclusive events involving the emission of two nucleons in (anti) neutrino charged-current scattering. The analysis is conducted within the framework of relativistic mean-field theory applied to nuclear matter. To quantify the likelihood of such semi-inclusive events occurring, we employ a relativistic model of meson-exchange currents that aligns with the 2p2h inclusive cross section. The outcomes are presented in terms of onefold and twofold integrated semi-inclusive cross sections. To highlight disparities among the various emission channels, including proton-proton, neutron-proton, and neutron-neutron, we compare them against a purely phase-space isotropic distribution within the center of mass of the two nucleons. These comparisons reveal significant differences in the event distributions, shedding light on the distinctive characteristics of each channel.

The influence of the spin cut-off parameter on the isomeric cross-section ratio of the $(n,2n)$ reaction is studied within the Huizenga-Vandenbosch method, in which the neutron transmission coefficient is evaluated from the optical model, and the spin cut-off parameter is treated for the residual nucleus following the first neutron emission $\left({\sigma }_1\right)$ and that following the second neutron emission $\left({\sigma }_2\right)$ separately. It is found that the isomeric cross-section ratio is definitely sensitive to the spin cut-off parameters, especially the ${\sigma }_2$. Moreover, various formulas of the spin cut-off parameters are compared and applied to calculate the $(n,2n)$ isomeric ratios of a series of nuclei from ${}^{45}\mathrm{Sc}$ to ${}^{198}\mathrm{Hg}$ at $E_n=14$ MeV, and the results are compared with the evaluated values from JENDL-5 and JEFF-3.3, which shows that the method is more reliable in the light- and medium-mass region, and most of the calculated results are described well by the formulas giving the lower spin cut-off parameters than the rigid-body formula, indicating that the effective moment of inertia is less than the rigid body moment of inertia for most nuclei. Furthermore, with the above method the overall isomeric ratios as a function of the incident energy for ${}^{45}\mathrm{Sc}{(n,2n)}^{44m,g}\mathrm{Sc}$, ${}^{85}\mathrm{Rb}{(n,2n)}^{84m,g}\mathrm{Rb}$, and ${}^{120}\mathrm{Te}{(n,2n)}^{119m,g}\mathrm{Te}$ reactions are well described, which shows the validity of the present method in calculating the isomeric ratio of the $(n,2n)$ reaction below 20 MeV.

Background: In recent years, the NUMEN project has highlighted that the systematic study of double charge exchange (DCE) nuclear reactions could provide precious information on the nuclear matrix elements of neutrinoless double $\beta$ decay. To achieve this goal, a multichannel approach was adopted, where a plethora of different reaction channels is measured under the same experimental conditions and analyzed in a coherent framework. In this context, the initial (ISI) and final (FSI) state interactions are fundamental building blocks to investigate all the relevant direct nuclear reactions. To date, such building blocks are not sufficiently established for many of the projectile-target pairs of interest for NUMEN experiments. This is also the case of the ${}^{18}\mathrm{O}+{}^{48}\mathrm{Ti}$ system, which is relevant for the double $\beta$ decay of the ${}^{48}\mathrm{Ca}$ nucleus into the ${}^{48}\mathrm{Ti}$ one.

Purpose: This work aims at deducing the ISI to be used in the multichannel study of the ${}^{18}\mathrm{O}+{}^{48}\mathrm{Ti}$ collision at 275 MeV incident energy. To this purpose, the optical potential and the strength of the couplings between elastic and inelastic scattering channels are determined and characterized by comparison with new experimental data.

Methods: Cross section angular distributions were measured for the elastic and low-lying inelastic scattering channels in a wide range of momentum transfer. Experimental data were compared to theoretical calculations performed in optical model (OM), distorted-wave Born approximation (DWBA), coupled channels (CC), and coupled channels equivalent polarization potential (CCEP) approaches. For all of them, the São Paulo double-folding potential was adopted as the optical potential. The comparison between the predictions of the OM/DWBA and CC frameworks allowed to evaluate the strength of the couplings to the inelastic channels which were explicitly taken into account. Within the CC formalism, different coupling schemes were compared to assess the contributions of the states included in the model space. A further test of our approach was carried out by analyzing the experimental data of the same system at 54 MeV incident energy.

Results: The achieved energy resolution allowed to resolve the elastic scattering and the excitation of the $2_1^{+}$ state of the ${}^{48}\mathrm{Ti}$ nucleus. A broad structure, associated to the superposition of the inelastic transitions to the $2_1^{+}$ state of ${}^{18}\mathrm{O}$ and to three excited states of ${}^{48}\mathrm{Ti}$, was also observed. The OM and DWBA calculations are not able to reproduce the experimental elastic and inelastic angular distributions in the explored range of momentum transfer. A significant improvement in the description of the data is found by using the CC approach. In particular, when the $2_1^{+}$ and $3_1^{-}$ collective states of projectile and target and their simultaneous excitations are included in the coupling scheme, a satisfactory agreement is achieved. The CCEP predictions describe reasonably well the elastic scattering data.

Conclusions: Channel coupling effects have to be taken into account for a good description of the elastic and inelastic experimental angular distributions in the measured range of momentum transfer. The inclusion of such couplings in the ISI is envisaged for the analysis of all the direct nuclear reactions induced by the ${}^{18}\mathrm{O}+{}^{48}\mathrm{Ti}$ collision in this incident energy region.

The study of the angular momentum properties of fission fragments can shed light on the complex mechanisms that characterize the fission process. One quantity that is of significant interest, and has not yet been studied adequately, is the alignment of the fragments, which is the cause of anisotropy of the $\gamma$ rays along the fission axis and has been observed in various past and recent experiments. In this work, we have performed calculations using the fifrelin code, in an attempt to quantify the alignment of the nuclear spins after neutron emission. Under the statistical tensor formalism of angular distributions, the conversion electron and $\gamma$-ray angular distributions can be treated simultaneously in an event-by-event calculation. This enables a first prediction of the conversion electron angular distribution with respect to the fission axis. An average value for the alignment of fission fragments is deduced for ${}^{252}\mathrm{Cf}$, with the use of recent experimental data. The method used for the present work can serve as a starting point for future theoretical and experimental studies in terms of $\gamma$ and conversion electron spectroscopy in view of studying the spin alignment of individual fission fragments, which could further improve our understanding on the process of fission.

We apply a large-scale summation of Feynman diagrams, including the class of parquet-diagrams plus important contributions outside the parquet class, for calculating effective pairing interactions and subsequently the superfluid gap in $P$-wave pairing in neutron matter. We employ realistic nucleon-nucleon interactions of the $v_8$ type and perform calculations up to a Fermi momentum of $1.8{\mathrm{fm}}^{-1}$. We find that many-body correlations lead to a strong reduction of the spin-orbit interaction, and, therefore, to an almost complete suppression of the ${}^{3}P_2$ and ${}^{3}P_2\text{−}{}^{3}F_2$ gaps. We also find pairing in ${}^{3}P_0$ states; the strength of the pairing gap depends sensitively on the potential model employed. Our results for triplet pairing are relevant for assessing superfluidity in neutron star interiors, whose presence can affect the cooling of neutron stars.

We investigate the azimuthal angle dependent local hydrodynamic helicity polarization of $\mathrm{\Lambda }$ hyperons, defined as the projection of the spin polarization vector along the directions of particle momenta, at BNL Relativistic Heavy Ion Collider beam energy scan energies by utilizing the relativistic ($3+1$)D CLVisc hydrodynamics framework with SMASH initial conditions. As opposed to local spin polarization at high energy collisions, our hydrodynamic simulations demonstrate that the azimuthal angle dependent helicity polarization induced by the kinetic vorticity dominates over other contributions at intermediate and low collision energies. Our findings provide an opportunity to probe the fine structure of local kinetic vorticity as a function of azimuthal angle at intermediate and low collision energies by mapping our predictions to the future measurements in experiments.

The weak charge of the proton $Q_{\text{w}}$ is one of the most fundamental quantities in physics. It can be determined by measuring the parity asymmetry $A_{\text{PV}}$ in elastic $ep$ scattering, where the $\gamma Z$-exchange contributions are crucial. For the past fifteen years, dispersion relations (DRs) in the forward limit have been widely used as a model-independent method to estimate these contributions. In this work, we study corrections to these forward-limit DRs. We first estimate these corrections using pointlike interactions as an illustrative example. We then estimate the $\gamma Z$-exchange contributions for the upcoming P2 experiment through both direct calculation and the forward-limit DRs, within the framework of low-energy effective interactions. The results indicate that the correction to the forward-limit DR for ${\square }_{\gamma Z}^V$ is around 47% for the upcoming P2 experiment, which will significantly modify the extracted value of $Q_{\text{w}}$.