The nucleon spin polarization perpendicular to the reaction plane ($P_y$) and along the beam direction ($P_z$) in $\mathrm{Au}+\mathrm{Au}$ collisions at the beam energy of $100\mathrm{A}\mathrm{MeV}$ with different nuclear spin-orbit interactions has been studied based on a spin- and isospin-dependent Boltzmann-Uehling-Uhlenbeck transport model. While the spin polarization is weaker with a weaker nuclear spin-orbit coupling as intuitively expected, a density-dependent nuclear spin-orbit coupling enhances the $P_y$ at large rapidities and leads to a less negative or large $P_y$ at high transverse momenta. The difference in the $P_y$ of free neutrons and protons at midrapidities and at small transverse momenta is sensitive to the isospin dependence of the nuclear spin-orbit interaction. While the $P_z$ is also affected by the properties of nuclear spin-orbit interaction in some sense, the behavior of the $P_y$ serves as a good probe of the strength, density dependence, and isospin dependence of nuclear spin-orbit interaction.

We report inclusive breakup measurements of the proton halo nucleus ${}^8\mathrm{B}$ on a medium mass target, ${}^{90}\mathrm{Zr}$. The experiment was carried out at the TriSol facility of the University of Notre Dame at a beam energy of 26.5 MeV, corresponding to 90% of the Coulomb barrier. The data include angular distributions of the ${}^7\mathrm{Be}$ breakup fragment and of the elastically scattered ${}^8\mathrm{B}$ nuclei, allowing a good normalization of the ${}^7\mathrm{Be}$ yields. The latter are found to be in good agreement with the prediction of continuum-discretized coupled-channel calculations, thus pointing to the direct excitation to the continuum as the main production mechanism. The integrated breakup cross section, ${\sigma }_{\mathrm{bu}}=170\pm 40$ mb, exhausts most of the total reaction cross section, indicating the dominance of direct processes below the barrier. A comparison of all existing breakup cross sections, on various targets at sub- and near-barrier energies, is also included.

Inclusive $e^{+}{e}^{-}$ production has been studied with HADES in ${\pi }^{-}+p, {\pi }^{-} +$ C, and ${\pi }^{-}+{\mathrm{CH}}_2$ reactions, using the GSI pion beam at $\sqrt{s_{\pi p}}=1.49$ GeV. Invariant mass and transverse momentum distributions have been measured and reveal contributions from Dalitz decays of ${\pi }^0, \eta$ mesons, and baryon resonances. The transverse momentum distributions are very sensitive to the underlying kinematics of the various processes. The baryon contribution exhibits a deviation up to a factor seven from the QED reference expected for the dielectron decay of a hypothetical pointlike baryon with the production cross section constrained from the inverse $\gamma n\to {\pi }^{-}p$ reaction. The enhancement is attributed to a strong four-momentum squared dependence of the timelike electromagnetic transition form factors as suggested by vector meson dominance (VMD). Two versions of the VMD that differ in the photon-baryon coupling have been applied in simulations and compared to data. VMD1 (or two-component VMD) assumes a coupling via the $\rho$ meson and a direct coupling of the photon, while in VMD2 (or strict VMD) the coupling is only mediated via the $\rho$ meson. The VMD2 model, frequently used in transport calculations for dilepton decays, is found to overestimate the measured dielectron yields, while a good description of the data can be obtained with the VMD1 model assuming no phase difference between the two amplitudes. Similar descriptions have also been obtained using a timelike baryon transition form factor model where the pion cloud plays the major role.

A recently formulated extension of perfect spin hydrodynamics, which includes second-order corrections in the spin polarization tensor to the energy-momentum tensor and baryon current, is studied in the case of a one-dimensional boost-invariant expansion. The presence of second-order corrections introduces feedback from spin dynamics on the hydrodynamic background, constraining possible spin polarization configurations. However, as long as the magnitude of the spin polarization tensor remains small (below unity in natural units), the permitted spin dynamics differs very little from that found in the case without the second-order corrections.

Effective proton-neutron interactions, $V_{pn}$, in mirror nuclei are systematically analyzed using the ground-state atomic masses. A mirror symmetry of $V_{pn}$ is found for bound nuclei with a standard deviation of $\sigma =32$ keV. However, this mirror symmetry is apparently broken for some mirror-nuclei pairs when a proton-unbound nucleus is involved in extracting the $V_{pn}$ values. Such a mirror-symmetry breaking is attributed to the Thomas-Ehrman shift of the proton-unbound nucleus and is investigated by using the Gamow shell model. It is concluded that the Thomas-Ehrman shift originates mainly from reduced Coulomb energies in the proton-unbound nuclei due to the extended radial density distribution of valence protons.

We compute ground-state and dynamical properties of ${}^4\mathrm{He}$ and ${}^{16}\mathrm{O}$ nuclei using as input high-resolution, phenomenological nucleon-nucleon and three-nucleon forces that are local in coordinate space. The nuclear Schrödinger equation for both nuclei is accurately solved employing the auxiliary-field diffusion Monte Carlo approach. For the ${}^4\mathrm{He}$ nucleus, detailed benchmarks are carried out with the hyperspherical harmonics method. In addition to presenting results for the binding energies and radii, we also analyze the momentum distributions of these nuclei and their Euclidean response function corresponding to the isoscalar density transition. The latter quantity is particularly relevant for lepton-nucleus scattering experiments, as it paves the way to quantum Monte Carlo calculations of electroweak response functions of ${}^{16}\mathrm{O}$.

Based on the dinuclear system model, we investigate the asymmetric fusion-evaporation reactions for producing unknown ${}^{279–281}\mathrm{Nh}$ isotopes, with the objective of filling the gap between cold and hot fusion reactions. The optimal reaction channels for synthesizing ${}^{279–281}\mathrm{Nh}$ are predicted to be the $4n$- and $3n$-emission channels of the reaction ${}^{34}\mathrm{S}+{}^{249}\mathrm{Bk}$, along with the $4n$-emission channel of the reaction ${}^{36}\mathrm{S}+{}^{249}\mathrm{Bk}$. The corresponding maximum evaporation residue (ER) cross sections are 2.453 pb, 4.846 pb, and 5.879 pb, respectively. Additionally, we investigate the synthesis of neutron-rich isotopes ${}^{287,288}\mathrm{Nh}$, focusing on the $3n$-emission channel of the reactions ${}^{41}\mathrm{S}+{}^{249}\mathrm{Bk}$ and ${}^{42}\mathrm{S}+{}^{249}\mathrm{Bk}$, which exhibits ER cross sections of 7.050 pb and 0.823 pb, respectively. These predictions highlight the potential of S-induced asymmetric fusion reactions in the synthesis of new Nh isotopes.

The short-range correlation, induced by the tensor force in the isosinglet neutron-proton interaction channel, results in a high-momentum tail (HMT) in the single-nucleon momentum distributions $n\left(k\right)$ in nuclei. Within an isospin- and momentum-dependent Boltzmann-Uehling-Uhlenbeck transport model incorporating the nucleon HMT, we investigate the impact of in-medium nucleon-nucleon cross sections on nuclear stopping and collective flows in collisions of ${}^{197}\mathrm{Au}+{}^{197}\mathrm{Au}$ and four isobaric systems: ${}^{94}\mathrm{Kr}+{}^{94}\mathrm{Kr}$, ${}^{94}\mathrm{Zr}+{}^{94}\mathrm{Zr}$, ${}^{94}\mathrm{Mo}+{}^{94}\mathrm{Mo}$, and ${}^{94}\mathrm{Ru}+{}^{94}\mathrm{Ru}$. It is shown that the calculation can well reproduce the shape of FOPI data, although the values of $varxz$ are overestimated by approximately $9\%$ relative to the data when HMTs and inelastic medium $NN$ cross sections are included. By enhancing the HMTs and mitigating the reduction of inelastic medium $NN$ cross sections, we can achieve better agreement with the FOPI data in both shape and numerical value. While keeping the effect of HMTs, the ratio of nuclear stopping power $varxz$ from neutron-rich and neutron-deficient reaction systems (with the same mass number) ${}^{94}\mathrm{Kr}+{}^{94}\mathrm{Kr}$ and ${}^{94}\mathrm{Ru}+{}^{94}\mathrm{Ru}$ nearly completely counteracts the effect of the inelastic nucleon-nucleon medium cross section. Furthermore, we find that the elliptic flows of nucleons are highly sensitive to both the HMTs and the in-medium $NN$ scattering cross sections.

The elastic $\mathrm{neutron}\text{−}{}^3\mathrm{H}$ scattering at intermediate energies is studied using rigorous integral equations solved in the momentum-space partial-wave basis. The four-particle transition operators are expanded into multiple-scattering series in terms of subsystem transition operators. Various approximations resulting from truncation of the series in different ways are evaluated and their validity is investigated. They fail at lower energies but at higher energies provide a rough reproduction of exact results at small scattering angles. In the large-angle region all approximations fail heavily, indicating that the scattering amplitude results from a delicate interplay of many multiple-scattering terms. The partial-wave analysis reveals that the developed approximations are reliable in higher partial waves, and for practical calculations an efficient “hybrid” approach is proposed, combining exact amplitudes in lower partial waves with approximations in higher partial waves. The implications for often used approximation of the first order in two-body transition matrix and development of microscopic optical potentials are discussed.

Proton-neutron pairing and like-nucleon pairing are two different facets of atomic nuclear configurations. While like-nucleon pair condensates manifest their superfluidic nature in semimagic nuclei, it is not absolutely clear if there exists a $T=0$ proton-neutron pair condensate phase in $N=Z$ nuclei. With an explicit formalism of general pair condensate with good particle numbers, we optimize proton-neutron pair condensates for all $N=Z$ nuclei between ${}^{16}\mathrm{O}$ and ${}^{100}\mathrm{Sn}$, given shell model effective interactions. As comparison, we also optimize like-nucleon pair condensates for their semimagic isotones. Shannon entanglement entropy is a measurement of mixing among pair configurations, and can signal intrinsic phase transition. It turns out the like-nucleon pair condensates for semimagic nuclei have large entropies signaling an entangled phase, but the proton-neutron pair condensates end up not far from a Hartree-Fock solution with small entropy. With artificial pairing interaction strengths, we show that the general proton-neutron pair condensate can transit from an entangled $T=1$ phase to an entangled $T=0$ phase, i.e., pairing phase transition driven by external parameters. In the $T=0$ limit, the proton-neutron pair condensate optimized for ${}^{24}\mathrm{Mg}$ turns out to be a purely $T=0$ P-pair condensate with large entanglement entropy, although such cases may occur in cold atom systems, unlikely in atomic nuclei.

The electric dipole strength distribution in ${}^{58}\mathrm{Ni}$ between 6 and 20 MeV has been determined from proton inelastic scattering experiments at very forward angles at RCNP, Osaka. The experimental data are rather well reproduced by quasiparticle random-phase approximation calculations including vibration coupling, despite a mild dependence on the adopted Skyrme interaction. They allow an estimate of the experimentally inaccessible high-energy contribution above 20 MeV, leading to an electric dipole polarizability ${\alpha }_{\mathrm{D}}\left({}^{58}\mathrm{Ni}\right)=3.48\left(31\right){\mathrm{fm}}^3$. This serves as a test case for recent extensions of coupled-cluster calculations with chiral effective field theory interactions to nuclei with two nucleons on top of a closed-shell system.

In this work, the Langevin approach within the two-center shell model incorporated with the statistical evaporation model is applied to consistently describe the fission dynamics and the deexcitation process of primary fragments. The charge distribution and the ratio of the average neutron number to proton number of fission fragments, the preneutron and postneutron mass distributions, the total kinetic energy (TKE) distribution and the TKE-mass correlation of fragments, as well as the multiplicity and energy spectrum of prompt neutron in ${}^{235}\mathrm{U}$ fission induced by thermal and 14 MeV neutron are calculated with the present approach. The calculation results are overall in good agreement with available experimental data and GEF calculations. In addition, the excitation energy distribution of the fission fragments and the correlation between the neutron multiplicity and the TKE are studied within the present model and are highly reasonable. It is straightforward to extend the present approach to study the fission observables for high-energy neutron induced fission on actinides, where multichance fission plays a more important role.

Background: The primary goal of studying isospin dynamics via heavy-ion reactions is to explore the isospin dependence of effective interactions within the nuclear equation of state (EOS).

Purpose: This work aims to investigate the effects of nuclear incompressibility ($K_0$) on neutron-proton equilibration in projectile-like fragments (PLFs).

Method: We simulate ${}^{70}\mathrm{Zn}+{}^{70}\mathrm{Zn}$ collisions at 35 MeV/nucleon using the isospin-dependent quantum molecular dynamics (IQMD) model, coupled with the statistical decay code GEMINI.

Results: The IQMD calculations not only reproduce experimental data patterns but also reveal the dynamic mechanisms underlying the binary breakup of PLFs. The rotation of PLFs is influenced by the transformation of angular momentum, which is connected to the isoscalar component of the nuclear EOS. This connection explains why shifts in $K_0$ affect the description of neutron-proton equilibration as measured by PLF rotation. The calculations demonstrate that a model with a smaller $K_0$ paired with a softer symmetry energy, or a larger $K_0$ with a slightly stiffer symmetry energy, both offer better indications of neutron-proton equilibration.

Conclusion: Considering the uncertainty in $K_0$, the slope of the symmetry energy is constrained to $L=30\pm 10\mathrm{MeV}$, providing valuable insights into the nuclear EOS.

The article considers two approaches to the description of $P$-even $T$-odd asymmetries in the angular distributions of prescission α particles, as well as instantaneous neutrons and $\gamma$rays: the classical one, using the method of trajectory calculations, and the quantum one, based on the quantum theory of fission. It was shown that within the framework of the first quasiclassical approach using the method of trajectory calculations it is not possible to describe at one and sometime the mechanisms of appearance of $P$-even $T$-odd asymmetries, and the second quantum approach demonstrates the possibility of simultaneous description of the presented asymmetries.

Measurements of multistep cascade gamma-ray spectra from several low-lying $1^{+}$ resonances in the ${}^{239}\mathrm{Pu}(n,\gamma )$ reaction were made using the DANCE detector. The measured spectra are compared to spectra simulated using several models for the photon strength function and the nuclear level density, representing the first analysis of this nature on a fissile nucleus. In general, models of the photon strength function that included a strong $M1$ “scissors mode” contribution coupled with a Gilbert-Cameron nuclear level density provided a reasonable description of the spectra. Simulations using photon strength functions and nuclear level densities specifically for ${}^{240}\mathrm{Pu}$, extracted by the Oslo method, resulted in a very good representation of the measured spectra. Neutron-capture cross section calculations that included the scissors mode provided a good estimate of the previously measured values, without additional normalization. However, the scissors-mode energy that produced the best description of the multistep cascade spectra was different from the value that best reproduced the capture cross section. In addition, the $\langle {\mathrm{\Gamma }}_{\gamma }\rangle$ inferred from the multistep cascade calculations was somewhat less than the tabulated value, which was determined from resonance analysis.

Here we report on the direct measurement of the resonance strengths of the $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$ and 1842 keV resonances in the ${}^{40}\mathrm{Ca}(p,\gamma ){}^{41}\mathrm{Sc}$ reaction. At novae temperatures, $0.2<T_9<0.7$, the ${}^{40}\mathrm{Ca}(p,\gamma ){}^{41}\mathrm{Sc}$ reaction is governed by the low energy resonance at $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$, whereas the $E_{\mathrm{R}}^{\mathrm{lab}}=1842\mathrm{keV}$ resonance serves as a normalization standard for nuclear reaction experiments within the astrophysically relevant energy range. For the $E_{\mathrm{R}}^{\mathrm{lab}}=647\mathrm{keV}$ resonance, we obtain a resonance strength $\omega \gamma =(2.51\pm 0.{09}_{\mathrm{stat}}\pm 0.{22}_{\mathrm{syst}})\mathrm{meV}$, with an uncertainty a factor of 2.5 smaller than the previous direct measurement value. For the $E_{\mathrm{R}}^{\mathrm{lab}}=1842\mathrm{keV}$ resonance, we obtain a resonance strength $\omega \gamma =(0.148\pm 0.{006}_{\mathrm{stat}}\pm 0.{013}_{\mathrm{syst}})\mathrm{eV}$, which is consistent with previous studies but deviates by $2\sigma$ from the most recent measurement. Our results suggest ${}^{40}\mathrm{Ca}$ to be a strong waiting point in the nucleosynthesis path of oxygen-neon (ONe) novae.

The equations of perfect spin hydrodynamics are solved for the first time using a realistic $(3+1)$-dimensional hydrodynamic background, calibrated to reproduce a comprehensive set of hadronic observables, including rapidity distributions, transverse momentum spectra, and elliptic flow coefficients for $\mathrm{Au}+\mathrm{Au}$ collisions at the beam energy of $\sqrt{s_{NN}}=200\mathrm{GeV}$. The spin dynamics is governed by the conservation of the spin tensor, describing spin-1/2 particles, with particle mass in the spin tensor treated as an effective parameter. We investigate several scenarios, varying both the effective mass and the initial evolution time for the spin polarization tensor. The model predictions are then compared with experimental measurements of global and longitudinal spin polarization of Λ hyperons. Our results indicate that a successful description of the data requires a delayed initial evolution time for the perfect spin hydrodynamics of about $4\mathrm{fm}/c$ (in contrast to the standard initial time of $1\mathrm{fm}/c$ used for the hydrodynamic background). This delay marks a transition from the phase where spin-orbit interaction is significant to the regime where spin-conserving processes dominate. Our findings suggest that the spin-orbit dissipative interaction plays a significant role only in the very early stages of the system's evolution.

Fission fragment mass distribution has been studied for the reaction ${}^{30}\mathrm{Si}+{}^{176}\mathrm{Yb}$ populating the compound nucleus ${}^{206}\mathrm{Po}$ at near-barrier energies to understand the effects of entrance channel mass asymmetry and deformation in the preactinide region. No appreciable deviation from a single Gaussian fit to the experimental mass distribution shows a nearly symmetric mass split for the composite system at the present experimental energy range. The experimentally measured fission fragments mass variance for ${}^{30}\mathrm{Si}+{}^{176}\mathrm{Yb}$ has been compared with the more asymmetric reaction ${}^{12}\mathrm{C}+{}^{194}\mathrm{Pt}$ having mass asymmetry lying on either side of the ${\alpha }_{\mathrm{BG}}$ value. The statistical saddle point model (SSPM) calculations based on compound nucleus fission for the two reactions indicate the presence of quasifission in the ${}^{30}\mathrm{Si}+{}^{176}\mathrm{Yb}$ reaction. Moreover, the higher variance of mass distribution near and below barrier energies shows the effect of deformation of the projectile and target on quasifission. The experimental data are also compared with the fission of nearby systems. The present result is consistent with the earlier findings of evaporation residue (ER) cross section for the reaction ${}^{30}\mathrm{Si}+{}^{176}\mathrm{Yb}$, where suppression in the ER cross section is attributed to noncompound nucleus fission and its dependance on entrance channel properties.

We extend the recently developed quantum van der Waals quarkyonic matter framework to nonzero isospin asymmetries by utilizing the two-component van der Waals equation with a generalized excluded volume prescription. The isospin dependence of van der Waals interaction parameters is determined by constraints on the symmetry energy, slope of the symmetry energy, and nuclear ground state properties. We find that the speed of sound has a peak for all values of the asymmetry parameter, signifying a transition to quarkyonic matter. The quarkyonic matter onset density is found to have a mild dependence on isospin asymmetry, with specific details influenced by the isospin dependence of the repulsive interactions. We also incorporate leptonic degrees of freedom and explore the neutron star matter equation of state, calculating mass-radius relations and tidal properties of neutron stars. We find that quarkyonic matter supports heavy neutron stars with a maximum mass of at least 2.6 solar masses. We observe quantitatively different behavior for the excluded volume cases of isospin-blind ($b_n=b_{pn}$) and isospin-dependent ($b_n\ne b_{pn}$) repulsion, the latter being preferred by observational constraints.