Background: The study of additional terms in functionals is relevant to better describe nuclear structure phenomenology. Among these terms, the tensor one is known to impact nuclear structure properties, especially in neutron-rich nuclei. However, its effect has not been studied on the whole nuclear chart yet.

Purpose: The impact of terms corresponding to the tensor at the Hartree level is studied for infinite nuclear matter as well as deformed nuclei, by developing new density-dependent functionals including these terms. In particular, we study in details the improvement such a term can bring to the description of specific nuclear observables.

Methods: The framework of covariant energy density functional is used at the Hartree-Bogoliubov level. The free parameters of covariant functionals are optimized by combining Markov-chain Monte Carlo and simplex algorithms. A sensitivity analysis on these parameters is undertaken.

Results: An improvement of the rms binding energies, spin-orbit splittings, and gaps is obtained over the nuclear chart, including axially deformed ones, when including tensors terms. Small modifications of the potential energy surface and densities are also found. In infinite matter, the Dirac mass is shifted to a larger value, in better agreement with experiments.

Conclusions: Taking into account additional terms corresponding to the tensor terms in the vector-isoscalar channel at the Hartree level improves the description of nuclear properties, both in nuclei and in nuclear matter.

We present a new method to perform variation after projection in many-body systems on quantum computers that does not require performing explicit projection. The technique employs the notion of “oracle”, generally used in quantum search algorithms. We show how to construct the oracle and the projector associated with a symmetry operator. The procedure is illustrated for the parity, particle number, and total spin symmetries. The oracle is used to restore symmetry by indirect measurements using a single ancillary qubit. An illustration of the technique is made to obtain the approximate ground state energy for the pairing model Hamiltonian.

Muon catalyzed fusion ($\mu \mathrm{CF}$) has recently regained considerable research interest owing to several new developments and applications. In this regard, we have performed a comprehensive study of the most important fusion reaction, namely, ${\left(dt\mu \right)}_{J=v=0}\to \alpha +n+\mu +17.6\mathrm{MeV}$ or ${\left(\alpha \mu \right)}_{nl}+n+17.6\mathrm{MeV}$. The coupled-channel Schrödinger equation for the reaction is thus solved, satisfying the boundary condition for the muonic molecule ${\left(dt\mu \right)}_{J=v=0}$ as the initial state and the outgoing wave in the $\alpha n\mu$ channel. We employ the $dt\mu$- and $\alpha n\mu$-channel coupled three-body model. All the nuclear interactions, the $d\text{−}t$ and $\alpha \text{−}n$ potentials, and the $dt\text{−}\alpha n$ channel-coupling nonlocal tensor potential are chosen to reproduce the observed low-energy ($1–300$ keV) astrophysical $S$ factor of the reaction $d+t\to \alpha +n+17.6\mathrm{MeV}$, as well as the total cross section of the $\alpha +n$ reaction at the corresponding energies. The resultant $dt\mu$ fusion rate is $1.15\times {10}^{12}{\mathrm{s}}^{-1}$. Substituting the obtained total wave function into the $T$ matrix based on the Lippmann-Schwinger equation, we have calculated absolute values of the fusion rates ${\lambda }_{\mathrm{f}}^{\mathrm{bound}}$ and ${\lambda }_{\mathrm{f}}^{\mathrm{cont}.}$ going to the bound and continuum states of the outgoing $\alpha \text{−}\mu$ pair, respectively. We then derived the initial $\alpha \text{−}\mu$ sticking probability ${\omega }_S^0={\lambda }_{\mathrm{f}}^{\mathrm{bound}}/({\lambda }_{\mathrm{f}}^{\mathrm{bound}}+{\lambda }_{\mathrm{f}}^{\mathrm{cont}.})=0.857\%$, which is $\approx 7\%$ smaller than the literature values $(\approx 0.91\%–0.93\%)$ and can explain the recent observations (2001) at high D-T densities. We have much improved the sticking-probability calculation by employing the $D$-wave $\alpha \text{−}n$ outgoing channel with the nonlocal tensor-force $dt\text{−}\alpha n$ coupling and by deriving ${\omega }_S^0$ based on the absolute values of the ${\lambda }_{\mathrm{f}}^{\mathrm{bound}}$ and ${\lambda }_{\mathrm{f}}^{\mathrm{cont}.}$. We also calculate the absolute values for the momentum and energy spectra of the muon emitted during the fusion process. The most important result is that the peak energy is 1.1 keV although the mean energy is 9.5 keV owing to the long higher-energy tail. This is an essential result for the ongoing experimental project to realize the generation of an ultraslow negative muon beam by utilizing the $\mu \mathrm{CF}$ for various applications, e.g., a scanning negative muon microscope and an injection source for the muon collider.

We calculate the cumulants and correlation functions of net-kaon multiplicity distributions in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=7.7$ GeV using a multiphase transport model (AMPT) with both a new coalescence mechanism and all charge conservation laws. The AMPT model can qualitatively describe the centrality dependences of the net-kaon cumulants and cumulant ratios measured by the STAR experiment. By focusing on the stage evolution of the cumulants, cumulant ratios, and correlation functions, we reveal several key effects on the fluctuations and correlations of strangeness during the dynamical evolution of relativistic heavy-ion collisions, including strangeness production and diffusion, hadronization, hadronic rescatterings, and weak decays. Without considering the quantum chromodynamics critical fluctuations in the dynamic model, we demonstrate that the net-kaon fluctuations can largely represent the net-strangeness fluctuations. Our results provide a baseline for understanding the net-kaon and net-strangeness fluctuations, which help to search for the possible critical behaviors at the critical end point in relativistic heavy-ion collisions.

We present a new study of jet interactions in the quark-gluon plasma created in high-energy heavy-ion collisions, using a multistage event generator within the jetscape framework. We focus on medium-induced modifications in the rate of inclusive jets and high transverse momentum (high-$p_{\mathrm{T}}$) hadrons. Scattering-induced jet energy loss is calculated in two stages: a high virtuality stage based on the matter model, in which scattering of highly virtual partons modifies the vacuum radiation pattern, and a second stage at lower jet virtuality based on the lbt model, in which leading partons gain and lose virtuality by scattering and radiation. Coherence effects that reduce the medium-induced emission rate in the matter phase are also included. The trento model is used for initial conditions, and the ($2+1$)dimensional vishnu model is used for viscous hydrodynamic evolution. Jet interactions with the medium are modeled via 2-to-2 scattering with Debye screened potentials, in which the recoiling partons are tracked, hadronized, and included in the jet clustering. Holes left in the medium are also tracked and subtracted to conserve transverse momentum. Calculations of the nuclear modification factor ($R_{\mathrm{AA}}$) for inclusive jets and high-$p_{\mathrm{T}}$ hadrons are compared to experimental measurements at the BNL Relativistic Heavy Ion Collider (RHIC) and the CERN Large Hadron Collider (LHC). Within this framework, we find that with one extra parameter which codifies the transition between stages of jet modification—along with the typical parameters such as the coupling in the medium, the start and stop criteria, etc.—we can describe these data at all energies for central and semicentral collisions without a rescaling of the jet transport coefficient $\widehat{q}$.

$Q_{\beta }$ represents one of the most important factors characterizing unstable nuclei, as it can lead to a better understanding of nuclei behavior and the origin of heavy atoms. Recently, machine learning methods have been shown to be a powerful tool to increase accuracy in the prediction of diverse atomic properties such as energies, atomic charges, and volumes, among others. Nonetheless, these methods are often used as a black box not allowing unraveling insights into the phenomena under analysis. Here, the state-of-the-art precision of the $\beta$-decay energy on experimental data is outperformed by means of an ensemble of machine-learning models. The explainability tools implemented to eliminate the black box concern allowed to identify proton and neutron numbers as the most relevant characteristics to predict $Q_{\beta }$ energies. Furthermore, a physics-informed feature addition improved models' robustness and raised vital characteristics of theoretical models of the nuclear structure.

We extend a semianalytical model that includes the finite nuclear thickness to calculate the energy density $\epsilon \left(t\right)$ and conserved-charge densities including the net-baryon density $n_{\mathrm{B}}\left(t\right)$ produced at mid-spacetime-rapidity in central Au + Au collisions. Assuming the formation of a quark-gluon plasma with an ideal gas equation of state of either quantum or Boltzmann statistics or with a lattice QCD-based equation of state, we extract the temperature $T$ and chemical potentials ${\mu }_{\mathrm{B}}, {\mu }_{\mathrm{Q}}$, and ${\mu }_{\mathrm{S}}$ as functions of time. This then allows us to semianalytically calculate the $T\text{−}{\mu }_{\mathrm{B}}$ trajectory of relativistic nuclear collisions in the QCD phase diagram, which should benefit the studies of high density physics including the search for the critical endpoint. This model is also useful for exploring the trajectories in the more general $T\text{−}{\mu }_{\mathrm{B}}\text{−}{\mu }_{\mathrm{Q}}\text{−}{\mu }_{\mathrm{S}}$ QCD phase space.

Deformed nuclei possess enhanced moments violating time reversal invariance ($T$) and parity ($P$). Collective magnetic quadrupole moments (MQM) appear in nuclei with a quadrupole deformation (which have ordinary $T,P$-conserving collective electric quadrupole moments). Nuclei with an octupole deformation have a collective electric octupole moment, electric dipole moment (EDM), Schiff moment, and MQM in the intrinsic frame which rotates with the nucleus. In a state with definite angular momentum in the laboratory frame, these moments are forbidden by $T$ and $P$ conservation, meaning their expectation values vanish due to nuclear rotation. However, nuclei with an octupole deformation have doublets of close opposite parity rotational states with the same spin, which are mixed by $T,P$-violating nuclear forces. This mixing polarizes the orientation of the nuclear axis along the nuclear spin, and all moments existing in the intrinsic frame appear in the laboratory frame (provided the nuclear spin $I$ is sufficiently large to allow such a moment). Such a mechanism produces enhanced $T,P$-violating nuclear moments. This enhancement also takes place in nuclei with a soft octupole vibration mode. In this paper we present updated estimates for the enhanced Schiff moment in isotopes of Eu, Sm, Gd, Dy, Er, Fr, Rn, Ac, Ra, Th, Pa, U, Np, and Pu in terms of the $CP$-violating $\pi$-meson–nucleon interaction constants ${\overline{g}}_0,{\overline{g}}_1$, and ${\overline{g}}_2$, the quantum chromodynamics parameter $\overline{\theta }$ and the quark chromo-EDMs. The implications of the enhanced $T,P$-violating moments to the search for axion dark matter in solid state experiments are also discussed, with potential alternative candidate compounds in which we may expect enhanced effects suggested.

We investigate the soft dipole resonance in the proton-rich nucleus ${}_6{}^8\mathrm{C}_2$, which is a collective dipole oscillation of four valence protons against the $\alpha$ core, and discuss the isospin symmetry with the mirror nucleus ${}_2{}^8\mathrm{He}_6$. We use the $\alpha +N+N+N+N$ five-body cluster model and many-body resonances are obtained using the complex-scaling method. The $1^{-}$ resonance of ${}_6{}^8\mathrm{C}_2$ is confirmed at the excitation energy of 13 MeV with a large decay width of 24 MeV, and its structure is similar to the soft dipole resonance in ${}_2{}^8\mathrm{He}_6$, such as the configuration mixing and the spatial properties. These results indicate a good isospin symmetry in the soft dipole resonances of two nuclei with a common collective excitation of multiproton and multineutron, while the ground states of two nuclei show different properties due to the Coulomb repulsion of valence protons in ${}_6{}^8\mathrm{C}_2$, leading to the symmetry breaking. In conclusion, the appearance of the isospin symmetry differs depending on the states of ${}_6{}^8\mathrm{C}_2$ and ${}_2{}^8\mathrm{He}_6$.

The $B(E2,0_1^{+}\to 2_1^{+})$ strengths of ${}^{36}\mathrm{Ca}$ and ${}^{38}\mathrm{Ca}$ are measured to be 131(20) $e^2{\mathrm{fm}}^4$ and 101(11) $e^2{\mathrm{fm}}^4$, respectively. The $B\left(E2\right)$ value for ${}^{36}\mathrm{Ca}$ required a measurement of the $p$/$\gamma$ branching ratio because the $2^{+}$ state is proton unbound. This branching ratio is $B_p=0.087\left(8\right)$. These $B\left(E2\right)$ and branching-ratio values can be reproduced in the shell-model with the ZMB2 interaction, an interaction that predicts the $Z=20$ $sd$-shell closure is incomplete with large proton $pf$-shell occupancies in the ground state. These occupancies are at odds with other shell-model and energy-density-functional calculations of ${}^{36}\mathrm{Ca}$. New data are used to provide an update on constraints of the density dependence of the symmetry energy through mirror charge-radii differences as well as to help reduce uncertainties of the astrophysical important ${}^{35}\mathrm{K}(p,\gamma$) reaction.

The role of pairing interactions on the scission configurations, the total kinetic energy, and the mass distributions in U isotopes is investigated using the deformed mean-field plus standard pairing model. The total kinetic energy and the mass distributions of ${}^{232–238}\mathrm{U}$ isotopes obtained using the shape-dependent probability distribution expressed by the Wigner function reproduces the experimental data remarkably well. The model calculations show that the scission region is sensitive to the variation of the pairing interaction strength, particularly for the asymmetric and symmetric scission points. The apparent changes in the peak-to-valley ratio in mass distribution by varying the pairing interaction strength confirm that the pairing interaction plays an important role in achieving the scission process for ${}^{236}\mathrm{U}$ under the present model. These results also suggest that the pairing interaction strength in the current work should increase with the elongation of the nucleus to yield better fission products. Through numerical analysis, we provide possible microscopic pictures of spontaneous fission around the scission configurations in the exactly solvable pairing model.

We report the measurement of $K^{*0}$ meson at midrapidity ($\left|y\right|<$ 1.0) in $\mathrm{Au}+\mathrm{Au}$ collisions at $\sqrt{s_{NN}}=7.7$, 11.5, 14.5, 19.6, 27, and 39 GeV collected by the STAR experiment during the Relativistic Heavy Ion Collider (RHIC) beam energy scan program. The transverse momentum spectra, yield, and average transverse momentum of $K^{*0}$ are presented as functions of collision centrality and beam energy. The $K^{*0}/K$ yield ratios are presented for different collision centrality intervals and beam energies. The $K^{*0}/K$ ratio in heavy-ion collisions are observed to be smaller than that in small-system collisions ($e+e$ and $p+p$). The $K^{*0}/K$ ratio follows a similar centrality dependence to that observed in previous RHIC and Large Hadron Collider measurements. The data favor the scenario of the dominance of hadronic rescattering over regeneration for $K^{*0}$ production in the hadronic phase of the medium.

Jets produced by the initial hard scattering in heavy ion collision events lose energy due to interactions with the color-deconfined medium formed around them: The quark-gluon plasma (QGP). Jet-medium interactions constitute an important theoretical and experimental field for studies of QGP, and various models with different assumptions have been proposed to describe them. A fair and direct comparison of these models requires that all other aspects of the simulation be fixed, which is achieved in this work by relying on the jetscape framework. We employ jetscape to directly and comprehensively compare two successful energy loss models: cujet and martini. We compare the models with the results of measurements of jet spectra and substructure observables. With the strong coupling tuned separately, we find that the two models broadly agree with each other in nuclear modification factors for charged hadrons and jets with cone size $R=0.4$. Systematic differences are reported in fragmentation functions, jet shape, and cone-size dependent jet $R_{AA}$.

The preequilibrium reaction mechanism is considered in the context of the exciton model. A modification to the one-particle–one-hole state density is studied which can be interpreted as a collective enhancement. The magnitude of the collective enhancement is estimated by simulating the Lawrence Livermore National Laboratory (LLNL) pulsed-spheres neutron-leakage spectra. The impact of the collective enhancement is explored in the context of the highly deformed actinide, ${}^{239}\mathrm{Pu}$. A consequence of this enhancement is the removal of fictitious levels in the distorted-wave Born approximation often used in modern nuclear reaction codes.

We have measured the cross section of the ${}^{83}\mathrm{Rb}(p,\gamma ){}^{84}\mathrm{Sr}$ radiative capture reaction in inverse kinematics using a radioactive beam of ${}^{83}\mathrm{Rb}$ at incident energies of 2.4 and $2.7A$ MeV. Prior to the radioactive beam measurement, the ${}^{84}\mathrm{Kr}(p,\gamma ){}^{85}\mathrm{Rb}$ radiative capture reaction was measured in inverse kinematics using a stable beam of ${}^{84}\mathrm{Kr}$ at an incident energy of $2.7A$ MeV. The effective relative kinetic energies of these measurements lie within the relevant energy window for the $\gamma$ process in supernovae. The central values of the measured partial cross sections of both reactions were found to be $0.17–0.42$ times the predictions of statistical model calculations. Assuming the predicted cross section at other energies is reduced by the same factor leads to a slightly higher calculated abundance of the $p$ nucleus ${}^{84}\mathrm{Sr}$, caused by the reduced rate of the ${}^{84}\mathrm{Sr}(\gamma ,p){}^{83}\mathrm{Rb}$ reaction derived from the present measurement.

Heavy-ion collisions at center-of-mass nucleon collision energies 4.5–11.5 GeV are analyzed within the parton-hadron-string dynamics (PHSD) transport model. Spectator nucleons are separated, and the transfer of the initial angular momentum of colliding nuclei to the fireball formed by participants is studied. The maximal angular momentum is carried by the fireball in gold-gold collisions with the impact parameter about 5 fm corresponding to centrality class 10–20%. The obtained participant distributions were fluidized and the energy and baryon number densities, temperature, and velocity fields are obtained in the Landau frame. It is shown that the velocity field has dominantly Hubble-like transversal and longitudinal expansion with the vortical motion being only a small correction on top of it. The vorticity field is calculated and illustrated in detail. The formation of two oppositely rotating vortex rings moving in opposite directions along the $z$ axis is demonstrated. Other characteristics of the vortical motion such as the Lamb vector field and the kinematic vorticity number are considered. The magnitude of the latter one is found to be smaller than that for the Poiseuille flow and close to the pure shear deformation corresponding to just a flattening of fluid cells. The field of hydrodynamic helicity, which is responsible for the axial vortex effect, is calculated. The separation of positive and negative helicities localized in upper and lower semiplanes with respect to the reaction plane is shown. It is proved that the areas with various helicity signs can be probed by the selection of $\mathrm{\Lambda }$ hyperons with positive and negative projections of their momenta orthogonal to the reaction plane.

The transparency of the hadrons produced in the $\gamma (n,p){\pi }^{-}$ reaction in nuclei is calculated using the Glauber model modified by including the Fermi motion of the nucleon in the nucleus. Because the calculated results underestimate the measured transparency for the ${}^4\mathrm{He}$ nucleus, the Glauber model is further modified by incorporating the short-range correlation of the nucleon and the color transparency of the hadron in the nucleus. The nuclear transparency of the $\gamma (n,p){\pi }^{-}$ reaction is calculated for ${\theta }_{{\pi }^{-}}\left(\mathrm{c}.\mathrm{m}.\right)={50}^{\circ }, {70}^{\circ }$, and ${90}^{\circ }$. The calculated results are compared with the data reported for the ${}^4\mathrm{He}$ nucleus.

We derive the empirical formulas expressing the mass and gravitational redshift of a neutron star, whose central density is less than threefold the nuclear saturation density, as a function of the neutron-skin thickness or the dipole polarizability of ${}^{208}\mathrm{Pb}$ or ${}^{132}\mathrm{Sn}$, especially focusing on the eight Skyrme-type effective interactions. The neutron star mass and its gravitational redshift can be estimated within $\approx 10\%$ errors with our formulas, while the neutron star radius is also expected within a few $\%$ errors by combining the derived formulas. Owing to the resultant empirical formulas, we find that the neutron star mass and radius are more sensitive to the neutron-skin thickness of ${}^{208}\mathrm{Pb}$ than the dipole polarizability of ${}^{208}\mathrm{Pb}$ or ${}^{132}\mathrm{Sn}$.

The $\gamma$-strength function and the nuclear level density for the odd-odd, rare-earth nucleus ${}^{166}\mathrm{Ho}$ have been extracted from ${}^{163}\mathrm{Dy}(\alpha ,p\gamma ){}^{166}\mathrm{Ho}$ data using the Oslo method. A structure at $\approx 3$ MeV in the $\gamma$-strength function is interpreted as the $M1$ scissors resonance. By employing three different methods we find that its strength depends rather strongly on the modeling of the $E1$ strength, while its centroid does not. The ${}^{166}\mathrm{Ho}$ scissors resonance parameters are consistent with previous results on other rare-earth nuclei.