The non-equilibrium in momentum space of fragmenting sources in central heavy-ion collisions at Fermi energy is reproduced by partly compensating for the fermionic feature in the isospin-dependent quantum molecular dynamics model. A memory loss ratio is defined to investigate the degree of entrance channel memory loss. The incomplete memory loss and the linear correlation between the memory loss ratio and the normalized radial flow energy are found both from experimental data and calculations. The residual memory indicates that the global equilibrium is not achieved in central collisions. The local equilibrium is achieved only in a very small central region of the fragmenting source. Both the asymmetry distribution of the expansive flow and the deformation of the fragmenting source are the consequences of the residual memory. A method to extract the transversal-to-longitudinal axis ratio of the expanding fragmenting source is suggested.

Using the isospin-dependent quantum molecular dynamics model, we study the isospin effects on the peak center-of-mass energy ($E_{\mathrm{c}.\mathrm{m}.}^{\max }$) and peak multiplicity of intermediate mass fragments (${\langle N_{\text{IMF}}\rangle }^{\max }$). We compare our theoretical calculations (for stable systems) with experimental data and find a good agreement. We further extend this study to neutron-rich colliding pairs. We find that $E_{\mathrm{c}.\mathrm{m}.}^{\max }$ is insensitive to neutron content for the isotopic colliding pairs due to the intermixing of mass and isospin effects, while for the isobaric pairs, $E_{\mathrm{c}.\mathrm{m}.}^{\max }$ decreases with increase in the $N/Z$ ratio of the system. We also demonstrate clearly the dominance of symmetry energy over Coulomb repulsion. We also find that ${\langle N_{\text{IMF}}\rangle }^{\max }$ increases with the system mass but is insensitive to the isospin degree of freedom.

New parameter sets of the semi-realistic nucleon-nucleon interaction are developed by modifying the M3Y interaction but maintaining the tensor channels and the longest-range central channels. The modification is made so as to reproduce microscopic results of neutron-matter energies, in addition to the measured binding energies of doubly magic nuclei including ${}^{100}$Sn and the even-odd mass differences of the $Z=50$ and $N=82$ nuclei in the self-consistent mean-field calculations. Separation energies of the proton- or neutron-magic nuclei are shown to be in fair agreement with the experimental data. With the new parameter-sets M3Y-P6 and P7, the isotropic spin-saturated symmetric nuclear matter remains stable in the density range as wide as $\rho \lesssim 6{\rho }_0$, while keeping desirable results of the previous parameter set on finite nuclei. Isotope shifts of the Pb nuclei and tensor-force effects on shell structure are discussed.

Background: Mixed-symmetry $2^{+}$ states in vibrational nuclei are characterized by a sign change between dominant proton and neutron valence-shell components with respect to the fully symmetric $2^{+}$ state. The sign can be measured by a decomposition of proton and neutron transition radii with a combination of inelastic electron and hadron scattering [C. Walz et al., Phys. Rev. Lett. 106, 062501 (2011)]. For the case of ${}^{92}$Zr, a difference could be experimentally established for the neutron components, while about equal proton transition radii were indicated by the data.

Purpose: Determination of the ground-state (g.s.) transition strength of the mixed-symmetry $2_2^{+}$ state and verification of the expected vanishing of the proton transition radii difference between the one-phonon $2^{+}$ states in ${}^{92}$Zr.

Method: Differential cross sections for the excitation of one-phonon $2^{+}$ and $3^{-}$ states in ${}^{92}$Zr have been measured with the ($e,e^{\prime }$) reaction at the S-DALINAC in a momentum transfer range $q\simeq 0.3–0.6$ fm${}^{-1}$.

Results: Transition strengths $B(E2;2_1^{+}\to 0_1^{+})=6.18\left(23\right)$, $B(E2;2_2^{+}\to 0_1^{+})=3.31\left(10\right)$, and $B(E3;3_1^{-}\to 0_1^{+})=18.4\left(1.1\right)$ Weisskopf units are determined from a comparison of the experimental cross sections to quasiparticle-phonon model (QPM) calculations. It is shown that a model-independent plane wave Born approximation (PWBA) analysis can fix the ratio of $B\left(E2\right)$ transition strengths to the $2_{1,2}^{+}$ states with a precision of about 1$\%$. The method furthermore allows to extract their proton transition radii difference. With the present data $\Delta R=-0.12\left(51\right)$ fm is obtained.

Conclusions: Electron scattering at low momentum transfers can provide information on transition radii differences of one-phonon $2^{+}$ states even in heavy nuclei. Proton transition radii for the $2_{1,2}^{+}$ states in ${}^{92}$Zr are found to be identical within uncertainties. The g.s. transition probability for the mixed-symmetry state can be determined with high precision limited only by the available experimental information on the $B(E2;2_1^{+}\to 0_1^{+}$) value.

We present a microscopic calculation of the complete quasiparticle interaction, including central as well as noncentral components, in neutron matter from high-precision two- and three-body forces derived within the framework of chiral effective-field theory. The contributions from two-nucleon forces are computed in many-body perturbation theory to first and second order (without any simplifying approximations). In addition we include the leading-order one-loop diagrams from the next-to next-to leading order (N${}^2$LO) chiral three-nucleon force, which contribute to all Fermi liquid parameters except those associated with the center-of-mass tensor interaction. The relative-momentum dependence of the quasiparticle interaction is expanded in Legendre polynomials up to $L=2$. Second-order Pauli blocking and medium polarization effects act coherently in specific channels; namely, for the Landau parameters $f_1$, $h_0$, and $g_0$, which results in a dramatic increase in the quasiparticle effective mass as well as a decrease in both the effective tensor force and the neutron matter spin susceptibility. For densities greater than about half the nuclear matter saturation density ${\rho }_0$, the contributions to the Fermi liquid parameters from the leading-order chiral three-nucleon force scale in all cases approximately linearly with the nucleon density. The largest effect of the three-nucleon force is to generate a strongly repulsive effective interaction in the isotropic spin-independent channel. We show that the leading-order chiral three-nucleon force leads to an increase in the spin susceptibility of neutron matter, but we observe no evidence for a ferromagnetic spin instability in the vicinity of the saturation density ${\rho }_0$. This work sets the foundation for future studies of neutron matter response to weak and electromagnetic probes with applications to neutron star structure and evolution.

The prompt neutron and $\gamma$ emission from primary fission fragments are calculated for thermal neutron induced fission of ${}^{235}$U and ${}^{239}$Pu and for spontaneous fission of ${}^{252}$Cf using a Monte Carlo Hauser-Feshbach approach for the evaporation of the excited fission fragments. Remaining free model parameters, such as excitation energy sharing and initial spin distribution, are determined by comparison of the neutron emission characteristics with experimental data. Using the obtained parameters the $\gamma$-ray characteristics, e.g., $\gamma$ spectrum, multiplicity distribution, average multiplicity and energy, and multiplicity distribution, are calculated and compared with available experimental data.

The recent works by the present authors and their collaborator predicted that the real part of heavy-ion optical potentials changes its character from attraction to repulsion around the incident energy per nucleon $E/A=$ 200–300 MeV on the basis of the complex $G$-matrix interaction and the double-folding model (DFM) and revealed that the three-body force plays an important role there. In the present paper, we have analyzed the energy dependence of the coupling effect with the microscopic coupled channel (MCC) method and its relation to the elastic and inelastic-scattering angular distributions in detail in the case of the ${}^{12}$C $+$ ${}^{12}$C system in the energy range of $E/A=$ 100–400 MeV. The large channel coupling effect is clearly seen in the elastic cross section although the incident energies are enough high. The dynamical polarization potential (DPP) is derived to investigate the channel coupling effect. Moreover, we analyze the effect of the imaginary part of the coupling potential on elastic and inelastic cross sections.

Fusion cross sections were measured for ${}^8$B + ${}^{28}$Si at near-barrier energies by detecting the alpha particles produced in the evaporation process. The results present a small suppression with respect to one-barrier penetration model predictions, which could be attributed to incomplete fusion processes and do not differ appreciably from fusion cross sections obtained with weakly bound but stable projectiles on the same target. Comprehensive comparisons of fusion cross sections at sub- and near-barrier energies with various light weakly bound projectiles support a simple tunneling probability with slight modifications due to coupled-channel effects.

At a hadronic scale the effect of CP-violating interactions that typically appear in extensions of the Standard Model may be described by an effective Lagrangian, in which the operators are expressed in terms of lepton and partonic gluon and quark fields and ordered by their mass dimension, $k⩾4$. Using a global-symmetry-preserving truncation of QCD Dyson-Schwinger equations, we compute the $\rho$-meson's electric dipole moment (EDM), $d_{\rho }$, as generated by the leading dimension-four and dimension-five CP-violating operators and an example of a dimension-six four-quark operator. The two dimension-five operators, i.e., the quark EDM and quark chromo-EDM, produce contributions to $d_{\rho }$ whose coefficients are of the same sign and within a factor of 2 in magnitude. Moreover, should a suppression mechanism be verified for the $\theta$ term in any beyond-Standard-Model theory, the contribution from a four-quark operator can match the quark EDM and quark chromo-EDM in importance. This study serves as a prototype for the more challenging task of computing the neutron's EDM.

We explore the effects of nuclear masses on the temperature and neutron density conditions required for $r$-process nucleosynthesis using four nuclear mass models augmented by the latest atomic mass evaluation. For each model we derive the conditions for producing the observed abundance peaks at mass numbers $A\sim 80$, 130, and 195 under the waiting-point approximation and further determine the sets of conditions that can best reproduce the $r$-process abundance patterns ($r$-patterns) inferred for the solar system and observed in metal-poor stars of the Milky Way halo. In broad agreement with previous studies, we find that (1) the conditions for producing abundance peaks at $A\sim 80$ and 195 tend to be very different, which suggests that, at least for some nuclear mass models, these two peaks are not produced simultaneously; (2) the typical conditions required by the critical waiting-point (CWP) nuclei with the $N=126$ closed neutron shell overlap significantly with those required by the $N=82$ CWP nuclei, which enables coproduction of abundance peaks at $A\sim 130$ and 195 in accordance with observations of many metal-poor stars; and (3) the typical conditions required by the $N=82$ CWP nuclei can reproduce the $r$-pattern observed in the metal-poor star HD 122563, which differs greatly from the solar $r$-pattern. We also examine how nuclear mass uncertainties affect the conditions required for the $r$-process and identify some key nuclei including ${}^{76}$Ni to ${}^{78}$Ni, ${}^{82}$Zn, ${}^{131}$Cd, and ${}^{132}$Cd for precise mass measurements at rare-isotope beam facilities.

There are currently no models readily available that provide nucleon-nucleon spin-dependent scattering amplitudes at high energies ($s\ge 6$ ${\text{GeV}}^2$). This work aims to provide a model for calculating these high energy scattering amplitudes. The foundation of the model is Regge theory since it allows for a relativistic description and full spin dependence. We present our parametrization of the amplitudes, and show comparisons of our solutions to the data set we have collected. Overall the model works as intended, and provides an adequate description of the scattering amplitudes.

There have been very few measurements of the total cross section for $np$ scattering below 500 keV. To differentiate among $NN$ potential models, improved cross section data between 20 and 600 keV are required. We measured the $np$ and $n$C total cross sections in this energy region by transmission; a collimated neutron beam was passed through CH${}_2$ and C samples and transmitted neutrons were detected by a BC-501A liquid scintillator. Cross sections were obtained with a precision of 1.1–2.0$\%$ between 150 and 800 keV using ratios of normalized neutron yields measured with and without the scattering samples in the beam. In energy regions where they overlap, the present results are consistent with existing precision measurements and fill in a significant gap in the data between $E_n=150$ and 500 keV.

Through a complex shift of the time coordinate, a modification of Bjorken flow is introduced which interpolates between a glasma-like stress tensor at forward rapidities and Bjorken-like hydrodynamics around mid-rapidity. A Landau-like full-stopping regime is found at early times and rapidities not too large. Approximate agreement with BRAHMS data on the rapidity distribution of produced particles at top Relativistic Heavy Ion Collider (RHIC) energies can be achieved if the complex shift of the time coordinate is comparable to the inverse of the saturation scale. The form of the stress tensor follows essentially from symmetry considerations, and it can be expressed in closed form.

We present results from a new ab initio method that uses the self-consistent Gorkov-Green's function theory to address truly open-shell systems. The formalism has been recently worked out up to second order and is implemented here in nuclei on the basis of realistic nuclear forces. Benchmark calculations indicate that the method is in agreement with other ab initio approaches in doubly closed shell ${}^{40}$Ca and ${}^{48}$Ca. We find good convergence of the results with respect to the basis size in ${}^{44}$Ca and ${}^{74}$Ni and discuss quantities of experimental interest including ground-state energies, pairing gaps, and particle addition and removal spectroscopy. These results demonstrate that the Gorkov method is a valid alternative to multireference approaches for tackling degenerate or near-degenerate quantum systems. In particular, it increases the number of mid-mass nuclei accessible in an ab initio fashion from a few tens to a few hundred.

We study tensor and pairing effects on the quadruple deformation of neon isotopes based on a deformed Skyrme-Hartree-Fock model with BCS approximation for the pairing channel. We extend the Skyrme-Hartree-Fock formalism for the description of single- and double-$\Lambda$ hypernuclei adopting two different hyperon-nucleon interactions. It is found that the interplay of pairing and tensor interactions is crucial to derive the deformations in several neon isotopes. Especially, the shapes of ${}^{26,30}$Ne are studied in details in comparisons with experimentally observed shapes. Furthermore the deformations of the hypernuclei are compared with the corresponding neon isotopic cores in the presence of tensor force. We find the same shapes with somewhat smaller deformations for single $\Lambda$-hypernuclei compared with their core deformations. It is also pointed out that the latest version of hyperon interaction, the ESC08b model, having a deeper $\Lambda$ potential makes smaller deformations for hypernuclei than those of another NSC97f model.

The origin of pseudospin symmetry (PSS) and its breaking mechanism are explored by combining supersymmetry (SUSY) quantum mechanics, perturbation theory, and the similarity renormalization group (SRG) method. The Schrödinger equation is taken as an example, corresponding to the lowest-order approximation in transforming a Dirac equation into a diagonal form by using the SRG. It is shown that while the spin-symmetry-conserving term appears in the single-particle Hamiltonian $H$, the PSS-conserving term appears naturally in its SUSY partner Hamiltonian $\tilde{H}$. The eigenstates of Hamiltonians $H$ and $\tilde{H}$ are exactly one-to-one identical except for the so-called intruder states. In such a way, the origin of PSS deeply hidden in $H$ can be traced in its SUSY partner Hamiltonian $\tilde{H}$. The perturbative nature of PSS in the present potential without a spin-orbit term is demonstrated by the perturbation calculations, and the PSS-breaking term can be regarded as a very small perturbation on the exact PSS limits. A general tendency that the pseudospin-orbit splittings become smaller with increasing single-particle energies can also be interpreted in an explicit way.

An improved quark mass density-dependent model is applied to study the ground-state properties of axially deformed even-even nuclei using the deformed quark-meson coupling calculation. The present study is mainly focused on the nuclei with the available experimental data ranging from $Z=14$ to $Z=26$. The ground-state binding energies, two-neutron separation energies, two-proton separation energies, quadrupole deformations, and root-mean-square (rms) charge radii are studied. The shell effect of the neutron magic number $N=20$ can be demonstrated by our model. It has been shown that the improved quark mass density-dependent model can give a reasonable description of the axially deformed nuclei.

We investigate effects of a nuclear medium on antiquark distribution in nuclei by applying the results of a recently developed relativistically covariant self-consistent model for the pion and the isobar. We take into account Fermi motion, including Pauli blocking and binding effects on the nucleons and medium effects on the isobar and pion, leading to modest enhancement of the pion light-cone-momentum distribution in large nuclei. As a consequence, the Drell-Yan cross-sectional ratio with respect to the deuteron exceeds one only for small values of the light-cone momentum.

The ratio of symmetry energy coefficient to temperature $C_{\text{sym}}/T$ is extracted from different prescriptions using the isotopic as well as the isobaric yield distributions obtained in different projectile fragmentation reactions. It is found that the values extracted from our theoretical calculation agree with those extracted from the experimental data but they differ very much from the input value of the symmetry energy used. The best possible way to deduce the value of the symmetry energy coefficient is to use the fragment yield at the breakup stage of the reaction and it is better to use the grand canonical model for the fragmentation analysis. This is because the formulas that are used for the deduction of the symmetry energy coefficient are all derived in the framework of the grand canonical ensemble, which is valid only at the breakup (equilibrium) condition. The yield of “cold” fragments, either from the theoretical models or from experiments, when used for extraction of the symmetry energy coefficient using these prescriptions, might lead to the wrong conclusion.