Using the relativistic impulse approximation with empirical NN scattering amplitude and the nuclear scalar and vector densities from the relativistic mean-field theory, we evaluate the Dirac optical potential for neutrons and protons in asymmetric nuclear matter. From the resulting Schrödinger-equivalent potential, the high-energy behavior of the nuclear symmetry potential is studied. We find that the symmetry potential at fixed baryon density is essentially constant once the nucleon kinetic energy is greater than about 500 MeV. Moreover, for such a high-energy nucleon, the symmetry potential is slightly negative below a baryon density of about $\rho =0.22$ fm${}^{-3}$ and then increases almost linearly to positive values at high densities. Our results thus provide an important constraint on the energy and density dependence of nuclear symmetry potential in asymmetric nuclear matter.

Using a relativistic mean-field single-particle knockout model for $(e,e^{\text{'}})$ reactions on nuclei, we investigate approximate treatments of Coulomb distortion effects and the extraction of longitudinal and transverse structure functions. We show that an effective momentum approximation when coupled with a focusing factor provides a good description of the transverse contributions to the $(e,e^{\text{'}})$ cross sections for electron energies above 300 MeV on ${}^{208}\mathrm{Pb}$. This approximation is not as good for the longitudinal contributions even for incident electron energies above 1 GeV, and if one requires very precise extraction of longitudinal and transverse structure functions in the quasielastic region, one must utilize distortion factors based on a nuclear model and a more accurate inclusion of Coulomb distortion effects.

In the present paper we have studied γ-ray emission in coincidence with charged particles measured in binary processes for the collisions ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$, ${}^{46}\mathrm{Ti}$ at 10 MeV/nucleon. The comparison between γ-ray yields, obtained under identical conditions on the charged particles detected in coincidence, shows an extra yield of around 15 MeV for the ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$ collision. The analysis of the γ-charged fragment coincidence events, along with the study performed with the dynamical model CoMD-II, explains this effect as the result of a giant dipole resonance emission from the intermediate system, characterized by a high degree of coherence. The performed study aims to establish a link among pre-equilibrium γ-ray emission, initial charge/mass ratio memory effects in the intermediate system for the ${}^{40}\mathrm{Ca}+{}^{48}\mathrm{Ca}$ system at short time, and the achievement of a substantial charge/mass ratio or isospin equilibration of the primary fragments formed at longer time. Moreover, the presence of a remarkable extra yield in a restricted range of the γ-ray spectra suggests that this equilibration process evolves through a quasiresonant mechanism.

We investigate the structure of the nonlocal contributions to the potential part of the symmetry term of the nuclear equation of state (EOS). Such momentum dependence of the symmetry potential leads to a splitting of the effective masses of protons and neutrons in asymmetric matter that will directly affect the nucleus-nucleus reaction dynamics. Based on microscopic transport simulations we suggest some rather sensitive observables in collisions of neutron-rich (unstable) ions at intermediate energies. In particular we focus the attention on preequilibrium nucleon emissions. We discuss interesting correlations between the $N/Z$ content of the fast emitted particles and their rapidity or transverse momentum, that show a nice dependence on the prescription used for the effective mass splitting.

An isospin-dependent coupled-channel optical model potential containing a dispersive term with a nonlocal contribution is used to simultaneously fit the available experimental database (including strength functions and scattering radius) for neutron and proton scattering on strongly deformed ${}^{238}\mathrm{U}$ and ${}^{232}\mathrm{Th}$ nuclei. The energy range 0.001–200 MeV is covered. A dispersive coupled-channel optical model (DCCOM) potential with parameters that show a smooth energy dependence and energy-independent geometry are determined from fits to the entire data set. Calculations using the obtained DCCOM potential reproduce measured total cross-section differences between ${}^{232}\mathrm{Th}$ and ${}^{238}\mathrm{U}$ within experimental uncertainty. The isovector terms and the observed very weak dependence of the geometrical parameters on mass number A allow us to extend the derived potential parameters to neighboring actinide nuclei with great confidence.

Based on interaction potentials between a heavy quark and antiquark as extracted from recent QCD lattice calculations, we set up a Brueckner-type many-body scheme to study the properties of light (anti-) quarks in a quark-gluon plasma at moderate temperatures, $T\simeq$ 1–2 $T_c$. The quark-antiquark T matrix, including both color-singlet and color-octet channels, and corresponding quark self-energies and spectral functions are calculated self-consistently. The repulsive octet potential induces quasiparticle masses of up to 150 MeV, whereas the attractive color-singlet part generates resonance structures in the $q\text{−}\overline{q}$ T matrix, which in turn lead to quasiparticle widths of ~200 MeV. This corresponds to scattering rates of ~1 fm${}^{-1}$ and may reflect liquid-like properties of the system.

Complete characterization of particle production and emission in relativistic heavy-ion collisions is in general not feasible experimentally. This work demonstrates, however, that the availability of essentially complete pseudorapidity distributions for charged particles allows for a reliable estimate of the average transverse momenta and energy of emitted particles by requiring energy conservation in the process. The results of such an analysis for Au+Au collisions at $\sqrt{s_{\mathit{NN}}}=130$ and 200 GeV are compared with measurements of mean-$p_T$ and mean-$E_T$ in regions where such measurements are available. The mean-$p_T$ dependence on pseudorapidity for Au+Au collisions at 130 and 200 GeV is given for different collision centralities.

The half-life of the 830.2-keV isomeric state in ${}^{97}\mathrm{Sr}$, for which very different values are reported in the literature, has been measured. The experiment performed at the LOHENGRIN fission-fragment separator consisted of two independent measurements. The two measurements provided consistent results. The weighted average value, $T_{1/2}=526(13)$ ns, supports the interpretation of the 830.2-keV state in ${}^{97}\mathrm{Sr}$, as the ${9/2}^{+}$[404] neutron-hole configuration.

Analyses of multifragmentation in terms of the Fisher droplet model (FDM) and the associated construction of a nuclear phase diagram bring forth the problem of the actual existence of the nuclear vapor phase and the meaning of its associated pressure. We present here a physical picture of fragment production from excited nuclei that solves this problem and establishes the relationship between the FDM and the standard compound nucleus decay rate for rare particles emitted in first-chance decay. The compound thermal emission picture is formally equivalent to an FDM-like equilibrium description and avoids the problem of the vapor while also explaining the observation of Boltzmann-like distribution of emission times. In this picture, a simple Fermi gas thermometric relation is naturally justified and verified in the fragment yields and time scales. Low-energy compound nucleus fragment yields scale according to the FDM and lead to an estimate of the infinite symmetric nuclear matter critical temperature between 18 and 27 MeV depending on the choice of the surface energy coefficient of nuclear matter.

The study of fluctuations of particle multiplicities in relativistic heavy-ion reactions has drawn much attention in recent years, because they have been proposed as a probe for underlying dynamics and possible formation of quark-gluon plasma. Thus it is of uttermost importance to describe the baseline of statistical fluctuations in the hadron gas phase in a correct way. We performed a comprehensive study of multiplicity distributions in the full ideal hadron-resonance gas in different ensembles, namely grand canonical, canonical, and microcanonical, by using two different methods: Asymptotic expansions and full Monte Carlo simulations. The method based on asymptotic expansion allows a quick numerical calculation of dispersions in the hadron gas with three conserved charges at the primary hadron level, while the Monte Carlo simulation is suitable for studying the effect of resonance decays. Even though mean multiplicities converge to the same values, major differences in fluctuations for these ensembles persist in the thermodynamic limit, as pointed out in recent studies. We observe that this difference is ultimately related to the nonadditivity of the variances in the ensembles with exact conservation of extensive quantities.

The Bakamjian-Thomas procedure is used to develop a method for constructing relativistic, instant form models of the pion-nucleon system. A limited model space is used to illustrate the method. The model space consists of a single-nucleon subspace, a pion-nucleon subspace, a two-pion-nucleon subspace, and a pion-sigma meson-nucleon subspace. A Poincaré invariant mass operator is constructed that includes vertex interactions that couple the various subspaces, as well as renormalization terms. It is shown that the pion-nucleon elastic scattering and production amplitudes can be obtained from the solution of a single, three-dimensional, integral equation of the Lippmann-Schwinger type. The effective pion-nucleon potential that appears in this equation contains contributions from direct and crossed nucleon exchanges along with sigma exchange. The production amplitudes are of the form that arises in isobar models. The elastic scattering and production amplitudes satisfy unitarity. The method developed makes it possible to extend existing coupled-channel models of the pion-nucleon system to include three-particle channels in such a way that the requirements of special relativity and unitarity are satisfied exactly.

The projected shell model is used to study the positive parity bands in ${}^{124}\mathrm{Ce}$. The energy spectra, transition quadrupole moments, and gyromagnetic factors are calculated. The calculation reproduces the observed positive parity bands. The peak in g-factors at spin $I=14$ is predicted due to proton alignment arising from the two quasiparticle (2-qp) band crossing. The wave functions of yrast states at $I=14$ to 20 are dominated by the two quasiparticle (2-qp) states. Measurement of transition quadrupole moments and g-factors would be a strong test for our predictions.

We show that it is possible to restore broken symmetries associated with the Goldstone mode within the self-consistent random phase approximation (SCRPA) applied to the three-level Lipkin model. To do this, it is necessary to include the so-called scattering terms in the RPA operator. We determine one- and two-body densities as very convergent expansions in terms of the generators of the RPA basis. We show that SCRPA excitations correspond to the heads of some rotational bands in the exact spectrum.

We study the ground-state properties of heavy closed-shell nuclei such as ${}^{48}\mathrm{Ca}$, ${}^{90}\mathrm{Zr}$, ${}^{120}\mathrm{Sn}$, and ${}^{208}\mathrm{Pb}$ as well as ${}^4\mathrm{He}$, ${}^{16}\mathrm{O}$, and ${}^{40}\mathrm{Ca}$. Similar to our recent work, the local density approximation in the harmonic oscillator basis and different channel-dependent effective two-body interactions that are generated through the lowest-order constrained variational calculation for asymmetric nuclear matter with the Reid68Day, Reid68, and Δ-Reid68 potentials are used. Unlike nuclear matter, it is shown that Reid68 potential gives ground-state binding energies closer to the experimental data with respect to the Δ-Reid68 potential and there is not much difference between Reid68 and Reid68Day potentials, which have been define up to $J=5$. The different channel-dependent effective interactions ($J>2$) and one- and two-body density distribution functions are discussed and they are compared with the results of other approaches such as the Brueckner local density approximation, correlated basis function, variational fermion hypernetted chain, variational cluster Monte Carlo, Brueckner-Hartree-Fock, fermionic molecular dynamics, and coupled cluster. Finally it is concluded that the three-body force (isobar degrees of freedom) is very important for light (heavy) nuclei because in the most of recent many-body calculations, it is observed that the available two-body nuclear forces usually underbind light nuclei and overbind heavy nuclei and nuclear matter.

Significant extensions to the high-spin excitation spectrum of the $N=91$, 92, 93 isotopes ${}^{157,158,159}\mathrm{Dy}$ have been achieved using the high-efficiency γ-ray spectrometers Euroball and Gammasphere. These nuclei were populated via weak 3n or $\alpha \mathrm{xn}$ exit channels in fusion evaporation reactions. In ${}^{157}\mathrm{Dy}$, the yrast band has been extended to $I^{\pi }=\frac{101}{2}{}^{{}^{+}}$ (tentatively to $\frac{105}{2}{}^{{}^{+}})$ with four sideband structures (two of which are new) observed in the 35–50$\hslash$ spin range. In ${}^{158}\mathrm{Dy}$, three bands have been extended to ${42}^{+}({44}^{+}),{40}^{-}$, and ${41}^{-}({43}^{-})$, whereas in ${}^{159}\mathrm{Dy}$ the yrast band is observed to $\frac{81}{2}{}^{{}^{+}}(\frac{85}{2}{}^{{}^{+}})$. The high-spin behavior and band crossing systematics of the Dy isotopes and of the neighboring N = 91, 92, and 93 isotones are discussed in terms of rotational alignments and shape transitions. Cranked Nilsson-Strutinsky calculations without pairing have been performed for detailed comparisons with the very high-spin states observed in ${}^{157}\mathrm{Dy}$.

Cross sections from low-energy neutron-nucleus scattering have been evaluated using a coupled-channel theory of scattering. Both a coordinate-space and a momentum-space formalism of that coupled-channel theory are considered. A simple rotational model of the channel-interaction potentials is used to find results using two relevant codes, ECIS97 and MCAS, so that they may be compared. The very same model is then used in the MCAS approach to quantify the changes that occur when allowance is made for effects of the Pauli principle.

The parton distribution function of the pion in the valence region is extracted in a next-to-leading order analysis from Fermilab E-615 pionic Drell-Yan data. The effects of the parametrization of the pion's valence distributions are examined. Modern nucleon parton distributions and nuclear corrections were used and possible effects from higher twist contributions were considered in the analysis. In the next-to-leading order analysis, the high-x dependence of the pion structure function differs from that of the leading order analysis, but not enough to agree with the expectations of pQCD and Dyson-Schwinger calculations.

We examine charmed-strange mesons within the framework of the constituent quark model, focusing on the states with $L=1$. We are particularly interested in the mixing of two spin states that are involved in $D_{s1}(2536)$ and the recently discovered $D_{\mathit{sJ}}(2460)$. We assume that these two mesons form a pair of states with $J=1$. These spin states are mixed by a type of spin-orbit interaction that violates the total-spin conservation. Without assuming explicit forms for the interactions as functions of the interquark distance, we relate the matrix elements of all relevant spin-dependent interactions to the mixing angle and the observed masses of the $L=1$ quartet. We find that the spin-spin interaction, among various types of spin-dependent interactions, plays a particularly interesting role in determining the spin structure of $D_{s1}(2536)$ and $D_{\mathit{sJ}}(2460)$.

High-spin states in ${}^{162}\mathrm{Ho}$ have been populated in the reaction ${}^{160}\mathrm{Gd}$(${}^7\mathrm{Li}$, 5n) at a beam energy of 49 MeV. The K ${}^{\pi }=1^{-}$ band, the low-K Gallagher-Moszkowski (GM) partner band of known high-K(K ${}^{\pi }=6^{-}$) band, based on the configuration $\pi 7/2^{-}[523]\otimes \nu 5/2^{+}[642]$, and the K ${}^{\pi }=6^{+}$ band, the high-K GM partner band of known low-K($K^{\pi }=1^{+}$) band, based on the configuration $\pi 7/2^{-}[523]\otimes \nu 5/2^{-}[523]$, have been identified. GM splitting energies, defined as $\Delta E_{\mathrm{GM}}=E_{\mathrm{int}}^{K_{\langle }}-E_{\mathrm{int}}^{K_{\rangle }}$, 80 keV and −135 keV were extracted from these two sets of GM doublet bands, respectively. They are comparable with 65 keV and −145 keV, reported recently by Hojman et al. for the corresponding configurations $\pi 7/2^{-}[523]\otimes \nu 5/2^{+}[642]$ and $\pi 7/2^{-}[523]\otimes \nu 5/2^{-}[523]$ in ${}^{164}\mathrm{Ho}$, respectively.

Microscopic models suggest the occurrence of strong octupole correlations in nuclei with $N\approx 88$. To examine the signatures of octupole correlations in this region, the spdf interacting boson approximation model is applied to Sm isotopes with $N=86\text{−}92$. The effects of including multiple negative-parity bosons in this basis are compared with more standard one negative-parity boson calculations and are analyzed in terms of signatures for strong octupole correlations. It is found that multiple negative-parity bosons are needed to describe properties at medium spin. Bands with strong octupole correlations (multiple negative-parity bosons) become yrast at medium spin in ${}^{148,150}\mathrm{Sm}$. This region shares some similarities with the light actinides, where strong octupole correlations were also found at medium spin.