Spin-polarization response functions for the high-energy $(e\to {,e}^{\prime }p\to )$ reaction are examined by computing all 18 response functions for proton kinetic energies of 0.515 and 3.170 GeV from an ${}^{16}\mathrm{O}$ target. The Dirac eikonal formalism is applied to account for the final-state interactions. It is found to yield the response functions in good agreement with those calculated by partial-wave expansion at 0.5 GeV. We identify the response functions that are dominantly determined by the spin-orbit potential in the final-state interaction. Dependence on the Dirac- or Pauli-type current of the nucleon is investigated in the helicity-dependent response functions, and the normal-component polarization of the knocked-out proton is computed.

Calculations for fission and cluster decay of ${}^{76}\mathrm{Sr}$ are presented for this nucleus to be in its ground state or formed as an excited compound system in heavy-ion reactions. The predicted mass distribution, for the dynamical collective mass transfer process assumed for fission of ${}^{76}\mathrm{Sr},$ is clearly asymmetric, favoring α nuclei. Cluster decay is studied within a preformed cluster model, both for ground-state to ground-state decays and from excited compound system to the ground state(s) or excited states(s) of the fragments.

A formalism is developed to evaluate the energy distribution of light clusters inside an excited nucleus. Its importance in predicting emitted cluster spectra is demonstrated by comparison with experiment and other models.

Results are presented of an analysis of proton and charged pion azimuthal distributions measured with respect to the reaction plane in Au + Au collisions at a beam momentum of about 11$A$ GeV/$c$. The azimuthal anisotropy is studied as a function of particle rapidity and transverse momentum for different centralities of the collisions. The triple differential (in rapidity, transverse momentum, and azimuthal angle) distributions are reconstructed. A comparison of the results with a previous analysis of charged-particle and transverse energy flow as well as with model predictions are presented.

We study the effect of resonance decays on intensity interferometry for heavy ion collisions. Collective expansion of the source leads to a dependence of the two-particle correlation function on the pair momentum $\mathbf{K}$. This opens the possibility to reconstruct the dynamics of the source from the $\mathbf{K}$ dependence of the measured Hanbury-Brown–Twiss (HBT) radii. Here we address the question to what extent resonance decays can fake such a flow signal. Within a simple parametrization for the emission function we present a comprehensive analysis of the interplay of flow and resonance decays on the one- and two-particle spectra. We discuss in detail the non-Gaussian features of the correlation function introduced by long-lived resonances and the resulting problems in extracting meaningful HBT radii. We propose to define them in terms of the second-order $q$ moments of the correlator $C(\mathbf{q},\mathbf{K})$. We show that this yields a more reliable characterisation of the correlator in terms of its width and the correlation strength $\lambda$ than other commonly used fit procedures. The normalized fourth-order $q$ moments (kurtosis) provide a quantitative measure for the non-Gaussian features of the correlator. At least for the class of models studied here, the kurtosis helps separating effects from expansion flow and resonance decays, and provides the cleanest signal to distinguish between scenarios with and without transverse flow.

A new formulation of meson self-energies is introduced for $\sigma ,\omega ,\pi ,\rho ,\delta$, and $\eta$ mesons on the basis of the particle-hole-antiparticle representation. We have studied the difference between the meson self-energy (MSE) of this representation and the MSE of the traditional density-Feynman (DF) representation. It is shown that the new formulation describes exactly the physical processes such as particle-hole excitations or particle-antiparticle excitations, and that, on the other hand, the meson self-energy based on the DF representation includes unphysical components. By numerical calculations, the meson self-energies describing the particle-hole excitations are shown to be close to each other for most of the meson self-energy in low momentum $(R<\mathrm{}500\mathrm{}$ MeV) and low energy ${(R}_0<200\mathrm{}$ MeV). This fact implies that former calculations using the low momentum and low-energy part do not change greatly. The density part of the density-Feynman representation has been shown to have a resonant structure around the energy of particle-antiparticle excitation, which causes a large difference between the two representations in the meson spectrum calculations. Our investigation concludes that the former calculations based on the density-Feynman representation are not invalidated in many cases, but the particle-hole-antiparticle representation is more appropriate to treat exactly the physical processes.

We study the pionic decay of a possible dibaryon $d^{\prime }\to N+N+\pi$ in the microscopic quark shell model. The initial $d^{\prime }$ dibaryon wave function ($J^P{=0\mathrm{}}^{-},$ $T=0\mathrm{}$) consists of one 1ħω six-quark shell-model $s^{5}p[51{]}_X$ configuration. The most important final six-quark configurations $s^6[6{]}_X,$ $s^4{p}^2[42{]}_X,$ and ${(s}^4{p}^2-s^{5}2s\left)\right[6{]}_X$ are properly projected onto the $\mathrm{NN}$ channel. The final state $\mathrm{NN}$ interaction is investigated by means of two phase-equivalent—but off-shell different—potential models. We demonstrate that the decay width ${\Gamma }_{d^{\prime }}$ depends strongly on the short-range behavior of the $\mathrm{NN}$ wave function. In addition, the width ${\Gamma }_{d^{\prime }}$ is very sensitive to the mass and size of the $d^{\prime }$ dibaryon. For dibaryon masses slightly above the experimentally suggested value $M_{d^{\prime }}=2.065\mathrm{}\mathrm{GeV},$ we obtain a pionic decay width of ${\Gamma }_{d^{\prime }}\approx 0.18–0.32\mathrm{MeV}$ close to the experimental value ${\Gamma }_{d^{\prime }}\approx 0.5\mathrm{MeV}.$

We study nuclear physics in the chiral limit ${(m}_u,$ $m_d=0)$ in which the pion mass vanishes. We find that the deuteron mass is changed little, but that $P$-wave nucleon-nucleon scattering volumes are infinite. This motivates an investigation of the possibilities that there could be a two-nucleon ${}^3{P}_0$ bound state, and that the nuclear matter ground state is likely to be a condensed state of nucleons paired to those quantum numbers. However, the short distance repulsion in the nucleon-nucleon potential is not affected by the chiral limit and prevents such new chiral possibilities. Thus the chiral limit physics of nuclei is very similar to that of nature. Using the chiral limit to simplify QCD sum rule calculations of nuclear matter properties seems to be a reasonable approximation.

The connection between the linear $\sigma$ model and the Nambu–Jona-Lasinio model is investigated on the basis of a conventional Hartree-Fock approach. As a missing link, an intermediate model is used: a linear $\sigma$ model with quarks (including the Dirac sea) but no “Mexican hat.” This model is particularly convenient to study the conditions for soliton formation and the stability of the soliton when the Dirac sea is included.

The interaction between the hyperon and the nucleon is investigated in the SU(3) Skyrme model. The static potential, which is expanded in terms of the modified SU(3) rotation matrices, is obtained for several orientations with the Atiyah-Manton ansatz. The interaction is calculated for the NN, $\Lambda$N, and $\Sigma$N systems. The medium-range attraction of the central potential between $\Lambda$ and N is obtained by considering the $\Lambda$-$\Sigma$ mixing through the intermediate state.

We study the nonstrange scalar-isoscalar states of a generalized Nambu–Jona-Lasinio model that includes the ’t Hooft interaction and a model of confinement. We also include coupling of the $q\overline{q}$ states to the two-pion continuum in our analysis. (Our study is limited to energies $q^2<~1.8{\mathrm{GeV}}^2,$ since to go beyond $q^2=2.0\mathrm{}{\mathrm{GeV}}^2$ we need to change our method of calculation.) After introducing octet-singlet mixing we find two states, ${\sigma }_1$ and ${\sigma }_2,$ at energies of 1.00 and 1.28 GeV, respectively. The first of these is predominantly a SU(3) singlet, while the second state is rather strongly mixed. Of particular interest for nuclear physics is the behavior of the quark-quark $T$ matrix for small spacelike values of $q^2.$ Because of a strong $q^2$ dependence of the $T$ matrix at the opening of the two-pion continuum at $q^2{=4m}_{\pi }^2,$ the effective mass that parametrizes scalar-isoscalar exchange in the $T$ matrix is about 520 MeV. Thus, in a model of the nucleon-nucleon interaction, whose ingredients are a $T$ matrix for the interaction of off-mass-shell quarks and valence-quark nucleon form factors, we can provide a basis for the use of a low-mass effective σ meson in nuclear physics.

Based on thermofield dynamics, the temperature- and density-dependent effective mass and screening mass of ρ meson have been calculated. The effects of vacuum fluctuation corrections through effective nucleon mass are examined. We have shown that vacuum fluctuations give an important correction to the self-energy of the ρ meson and lead to a reduction of the ρ-meson mass in hot and dense matter. The temperature and density dependence of one-ρ-meson exchange potential with vacuum fluctuation correction is also given.

We extend the method of QCD sum rules in external fields to determine the $\rho \mathrm{NN}$ and $\omega \mathrm{NN}$ strong couplings, including both the vector and tensor couplings. Such information has been used for years in the construction of nuclear potentials, but our attempt represents the first direct contact with QCD in terms of the basic parameters associated with the nontrivial QCD vacuum.

An infinite system of nonlocal, individually confining solitons is considered as a model of high-density nuclear matter. The soliton-lattice problem is discussed in the Wigner-Seitz approximation. The cell size is varied to study the density dependence of physical quantities of interest. A transition to a system where quarks can migrate between solitons is found. We argue that this signals quark deconfinement. The model is applied to the calculation of selected in-medium properties.

We study pion-nucleon scattering at tree level with a chiral Lagrangian of pions, nucleons, and $\Delta$ isobars using a $K$-matrix unitarization procedure. Evaluating the scattering amplitude to order $Q^2$, where $Q$ is a generic small momentum scale, we obtain a good fit to the experimental phase shifts for pion center-of-mass kinetic energies up to 50 MeV. The fit can be extended to 150 MeV when we include the order-$Q^3$ contributions. Our results are independent of the off-shell $\Delta$ parameter.

Independent of assumptions about the form of the quark-quark scattering kernel $K$, we derive the explicit relation between the flavor-nonsinglet pseudoscalar-meson Bethe-Salpeter amplitude ${\Gamma }_H$ and the dressed-quark propagator in the chiral limit. In addition to a term proportional to ${\gamma }_5$, ${\Gamma }_H$ necessarily contains qualitatively and quantitatively important terms proportional to ${\gamma }_5\gamma \cdot P$ and ${\gamma }_5\gamma \cdot \mathrm{kk}\cdot P$, where $P$ is the total momentum of the bound state. The axial-vector vertex contains a bound state pole described by ${\Gamma }_H,$ whose residue is the leptonic decay constant for the bound state. The pseudoscalar vertex also contains such a bound state pole and, in the chiral limit, the residue of this pole is related to the vacuum quark condensate. The axial-vector Ward-Takahashi identity relates these pole residues, with the Gell-Mann–Oakes–Renner relation a corollary of this identity. The dominant ultraviolet asymptotic behavior of the scalar functions in the meson Bethe-Salpeter amplitude is fully determined by the behavior of the chiral limit quark mass function, and is characteristic of the QCD renormalization group. The rainbow-ladder Ansatz for $K$, with a simple model for the dressed-quark-quark interaction, is used to illustrate and elucidate these general results. The model preserves the one-loop renormalization group structure of QCD. The numerical studies also provide a means of exploring procedures for solving the Bethe-Salpeter equation without a three-dimensional reduction.

We estimate the lifetime of systems consisting of negative pions and neutrons (pineuts). We consider the direct decay of the pion as well as second-order diagrams involving the intermediate decay processes $n\to {p+e}^{-}+\overline{\nu }$ and ${\pi }^{-}\to {\pi }^0{+e}^{-}+\overline{\nu }$ by assuming a simple single-particle model. We found that the dominant process is that with an intermediate neutron decay which leads to a lifetime of around ${10}^{-8}$ sec.

Neutrino absorption cross sections for ${}^{71}\mathrm{Ga}$ are calculated for all solar neutrino sources with standard energy spectra, and for laboratory sources of ${}^{51}\mathrm{Cr}$ and ${}^{37}\mathrm{Ar}$; the calculations include, where appropriate, the thermal energy of fusing solar ions and use improved nuclear and atomic data. The ratio, $R,$ of measured (in GALLEX and SAGE) to calculated ${}^{51}\mathrm{Cr}$ capture rate is $R$=0.95±0.07 (expt)${+}_{\mathrm{-}0.03}^{+0.04\mathrm{}}$ (theor). Cross sections are also calculated for specific neutrino energies chosen so that a spline fit determines accurately the event rates in a gallium detector even if new physics changes the energy spectrum of solar neutrinos. Theoretical uncertainties are estimated for cross sections at specific energies and for standard neutrino energy spectra. Standard energy spectra are also presented for $\mathrm{pp}$ and CNO neutrino sources in the appendix. Neutrino fluxes predicted by standard solar models, corrected for diffusion, have been in the range 120 SNU to 141 SNU since 1968.

Decay properties of the high- and low-spin isomers of ${}^{154}\mathrm{Tm}$ were investigated following the on-line mass separation of $A=154\mathrm{}$ nuclides produced in ${}^{64}\mathrm{Zn}$ irradiations of ${}^{92}\mathrm{Mo}$ and ${}^{94}\mathrm{Mo}.$ The α-decay branching ratio of the high-spin isomer was determined and two γ rays were added to its $({\beta }^{+}+\mathrm{EC})$ decay. In addition, fine-structure peaks were observed in the α spectra of both isomers.

The relevance of the inner part of the potential barrier in an effective model to describe the prescission phase in nuclear disintegration processes is discussed under the assumption of spherical fragments. Although for the alpha decay process the inner part of the potential barrier is small, this is not the case for heavier cluster radioactivity and spontaneous cold fission processes. For the latter one, we remark that the molecular phase cannot be neglected in calculating Gamow’s penetrability factor used to obtain cold fission yields and half lives.