The Holstein-Primakoff boson mapping at finite temperature and in the framework of the thermo field dynamics (TFD) is applied to treat a fermion-boson Hamiltonian. The interaction between pairs of fermions and bosons is constructed in a model which allows for a condensate. The evolution of the condensate as a function of the temperature is investigated.

The effect of meson and isobar degrees of freedom in $A\left(\overrightarrow{e}{,e}^{\prime }\overrightarrow{p}\right)$ and ${A(e,e}^{\prime }n)$ is studied for four-momentum transfers $Q^2$ in the range between 0.2 and $0.8\hspace{0.5em}(\mathrm{GeV}{/c)}^2$. The calculations are performed in a nonrelativistic framework with explicit $(N,\Delta ,\pi )$ degrees of freedom. For the whole range of momentum transfers under investigation the effect of the meson-exchange and isobar degrees of freedom is significant. At low missing momenta and quasielastic conditions, a tendency to reduce the ${(e,e}^{\prime }p)$ and ${(e,e}^{\prime }n)$ differential cross sections is noticed. The greatest sensitivity is found in the interference structure functions $W_{\mathrm{LT}}$ and $W_{\mathrm{TT}}.$ The recoil polarization observables, on the other hand, are moderately affected by the meson-exchange and $\Delta$-isobar currents.

We use our covariant model of light-meson structure to study the $f_2$ tensor mesons. Our model is a generalized Nambu–Jona-Lasinio (NJL) model that includes a relativistic model of confinement. For the study of tensor mesons, we extend the NJL model to include interactions that contain gradients of the quark fields. There are two such terms requiring the introduction of two additional coupling constants for the model. We find a good fit to the experimentally determined states. We obtain ten states below 2 GeV, while there are eight states in the data tables with energies less than 2 GeV, if we include the recently found $f_J\mathrm{}\left(1750\right)\mathrm{}$ in our list of $f_2$ mesons. We find $f_2^{\prime }$ states of $s\overline{s}$ structure at 1551, 1745, and 1767 MeV. The first two of these states have nodeless wave functions and may be identified with the $f_2^{\prime }\mathrm{}\left(1525\right)\mathrm{}$ and the $f_J\mathrm{}\left(1750\right),$ if $J=2\mathrm{}$ for the new state. (The state at 1767 MeV is a $2S\hspace{0.5em}s\overline{s}$ state, which may mix with the 1745 MeV state to some degree.) Our analysis suggests a new classification for nonets of radially excited states that is based upon our relativistic model of light-meson structure.

Realistic solutions of the spinor-spinor Bethe-Salpeter equation for the deuteron with the realistic interaction kernel, including the exchange of $\pi ,$ $\sigma ,$ $\omega ,$ $\rho ,$ $\eta$, and $\delta$ mesons, are used to systematically investigate relativistic effects in inclusive quasielastic electron-deuteron scattering within the relativistic impulse approximation. Relativistic y scaling is considered by generalizing the nonrelativistic scaling function to the relativistic case, and it is shown that y scaling does occur in the usual relativistic scaling variable resulting from the energy conservation in the instant form of dynamics. The present approach of y scaling is fully covariant, with the deuteron being described by eight components, viz. the ${}^3{S}_1^{++},$ ${}^3{S}_1^{--},$ ${}^3{D}_1^{++},$ ${}^3{D}_1^{--},$ ${}^3{P}_1^{+-},$ ${}^3{P}_1^{-+},$ ${}^1{P}_1^{+-},$ ${}^1{P}_1^{-+}$ waves. It is demonstrated that if the negative relative energy states ${}^1{P}_1,$ ${}^3{P}_1$ are disregarded, the concept of covariant momentum distributions ${N(p}_0,\mathbf{p})$, with $p_0{=M}_D/2\mathrm{}-\sqrt{{\mathbf{p}}^2{+m}^2},$ can be introduced, and that calculations of electrodisintegration cross section in terms of these distributions agree within a few percent with the exact calculations, which include the ${}^1{P}_1$ and ${}^3{P}_1$ states, provided the nucleon three momentum $|\mathbf{p}|<~1\hspace{0.5em}\mathrm{GeV}/c;$ in this momentum range, the asymptotic relativistic scaling function is shown to coincide with the longitudinal covariant momentum distribution.

We derive three-body equations valid at finite densities and temperatures. The equations are based on the cluster mean field approach consistently including proper self-energy corrections and Pauli blocking. As an application we investigate the binding energies of triton and determine the Mott densities and momenta relevant for a many particle description of nuclear matter in a generalized Beth-Uhlenbeck approach. The method, however, is not restricted to nuclear physics problems but may also be relevant, e.g., to treat three-particle correlations in weakly doped semiconductors or strongly coupled dense plasmas.

The nuclear transparency and the distorted momentum distributions of ${}^4\mathrm{He}$ in the semi-inclusive process ${}^4\mathrm{He}{(e,e}^{\prime }p)X$ are calculated within the Glauber multiple scattering approach using for the first time realistic four-body variational wave functions embodying central and noncentral nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ correlations. The contributions from $\mathrm{NN}$ correlations and from Glauber multiple scattering are taken into account exactly to all orders. It is shown that noncentral correlations significantly affect both the transparency and the distorted momentum distributions; as a matter of fact (i) the small $(\approx 3\%)$ value of the effect of correlations on the transparency results from an appreciable cancellation between the short-range central repulsive correlations and the intermediate-range attractive correlations, whose magnitude is significantly affected by the noncentral forces, and (ii) the effect of Glauber final state interactions on the momentum distribution is reduced by the inclusion of tensor correlations.

The structure of the $\phi$ photoproduction amplitude in the $\sqrt{s}\sim 2-5\mathrm{GeV}$ region is analyzed based on Pomeron-exchange and meson-exchange mechanisms. The SU(3) symmetry and the $\phi$ decay widths are exploited to determine the parameters that are needed to predict the amplitudes due to pseudoscalar mesons $({\pi }^0,\eta )$ exchange, scalar mesons $\left(\sigma {,a}_0{,f}_0\right)$ exchange, and the $\phi$ radiation from the nucleon. In addition to the universally accepted Pomeron exchange with an intercept $\alpha \mathrm{}\left(0\right)\mathrm{}\sim 1.08,$ we investigate the role of a second Pomeron with $\alpha \mathrm{}\left(0\right)<0,$ as inspired by the glueball ${(J}^{\pi }{=0\mathrm{}}^{+}{,M}_b^2\sim 3{\mathrm{GeV}}^2)$ predicted by the lattice QCD calculation and dual Ginsburg-Landau model. It is found that the existing limited data at low energies near threshold can accommodate either the second Pomeron or the scalar mesons exchange. The differences between these two competing mechanisms are shown to have profound effects on various density matrices which can be used to calculate the cross sections as well as various single and double polarization observables. We predict a definite isotopic effect: polarization observables of $\phi$ photoproduction on the proton and neutron targets can have differences of a factor 2 and more.

We investigate the robustness of the purported correlation between the g-factor ratios in the $\gamma$ and ground bands and the corresponding $E2/M1\mathrm{}$ mixing ratios in the proton-neutron interacting boson model. We show that this correlation is dependent on the choice of the Hamiltonian and can be transgressed, when the parameters are chosen appropriately. The recent $M1\mathrm{}$ data in ${}^{168}\mathrm{Er},$ which do not exhibit such a correlation, are analyzed in the light of these results.

Using our previous approach to electromagnetic emission during tunneling, an explicit, essentially classical, formula describing the bremsstrahlung spectrum in a decay is derived. The role of tunneling motion in photon emission is discussed. The shape of the spectrum is a universal function of the ratio $E_{\gamma }{/E}_0,$ where $E_{\gamma }$ is the photon energy and $E_0$ is a characteristic energy depending only on the nuclear charge and the energy of the a particle.

Off-shell aspects of the one-pion-exchange potential and their relationship to different forms of the nonstatic (subleading-order) chiral two-pion-exchange nucleon-nucleon potential are discussed. Various types of off-shell behavior are categorized and numerous examples are given. Recently derived potentials based on chiral approaches are supplemented by a rather general form of the two-pion-exchange potential that is derived using old-fashioned methods and exhibits off-shell dependence. The latter potential is closely related to a general form of one-pion-exchange relativistic corrections and nonstatic two-pion-exchange three-nucleon forces developed long ago.

The lifetimes of 12 excited states in ${}^{134}\mathrm{Nd}$ were measured with a high precision by means of the GASP spectrometer applying the coincidence recoil-distance Doppler-shift method. The ${}^{110}\mathrm{Pd}{(}^{28}\mathrm{Si},xnyp)$ reaction was used at a beam energy of 125 MeV. The data were analyzed with the differential decay curve method and the derived lifetimes were used for a sensitive test of various nuclear models. The transition quadrupole moments ${(Q}_t)$ in the ground state band agree nicely with the predictions of both the rotor model and the O(6) symmetry of the interacting boson approximation up to the $4_g^{+}$ state of ${}^{134}\mathrm{Nd}.$ The $Q_t$ values for the $8_g^{+},$ ${10}_{S1\mathrm{}}^{+},$ and ${12}_{S1\mathrm{}}^{+}$ states, however, give evidence for a strong change of the nuclear deformation. The lifetimes of 12 low lying yrast states in the ${}^{130,131,132}\mathrm{Ce},$ ${}^{133,134}\mathrm{Pr},$ and ${}^{135}\mathrm{Nd}$ nuclei have been also determined.

The second-rank analyzing powers $T_{20}$ and ${}^T{T}_{20}$ were measured using a tensor-polarized beam of ${}^{23}\mathrm{Na}$ scattered from ${}^{27}\mathrm{Al}$ at an incident energy of 150 MeV. The concept of tidal symmetry in scattering systems leads directly to a shape-effect relationship between the two sets of analyzing powers which should hold good at low values of the isocentrifugal parameter and this has been confirmed in other scattering systems. $\mathrm{For}{\hspace{0.5em}}^{23}\mathrm{Na}{+}^{27}\mathrm{Al}$ at 150 MeV the isocentrifugal parameter has the low value of 0.04, yet the shape effect relations do not hold true for the data forward of $12°\hspace{0.5em}\mathrm{c}.\mathrm{m}.\mathrm{}$ It is suggested that this may be evidence for an effect of the deformation of the target nucleus and this is supported by coupled-channel calculations which agree well with the data.

The nucleon spin structure functions have been extracted from measurements of asymmetries in deep inelastic scattering of polarized leptons on polarized nuclei. The polarized nuclei present in practical targets: H, ${}^2\mathrm{H},$ ${}^3\mathrm{He},$ ${}^{14}\mathrm{N},$ ${}^{15}\mathrm{N},$ ${}^6\mathrm{Li},$ and ${}^7\mathrm{Li},$ are, with the exception of hydrogen, systems of bound nucleons, some of which can attain significant degrees of alignment. All the aligned nucleons contribute to the asymmetries. The contributions of each nuclear species to the asymmetry have to be carefully determined, before a reliable value for the net nucleon asymmetry is obtained. For this purpose, the spin component of the nuclear angular momentum for every nuclear state and the probability of each state have to be known with sufficient accuracy. In this paper I discuss the basic corrections used to estimate the contributions of the different nuclei, with emphasis on the $A=6\mathrm{}$ and 7 Li isotopes present in the ${\mathrm{Li}}^2\mathrm{H}$ polarized target used during SLAC Experiment 155 to study the deuteron spin structure.

A relativistic light-front formulation of nuclear dynamics is developed and applied to treating infinite nuclear matter in a method which includes the correlations of pairs of nucleons: this is light-front Brueckner theory. We start with a hadronic meson-baryon Lagrangian that is consistent with chiral symmetry. This is used to obtain a light-front version of a one-boson-exchange nucleon-nucleon potential (OBEP). The accuracy of our description of the nucleon-nucleon $\mathrm{}\left(\mathrm{NN}\right)\mathrm{}$ data is good, and similar to that of other relativistic OBEP models. We derive, within the light-front formalism, the Hartree-Fock and Brueckner-Hartree-Fock equations. Applying our light front OBEP, the nuclear matter saturation properties are reasonably well reproduced. We obtain a value of the compressibility 180 MeV that is smaller than that of alternative relativistic approaches to nuclear matter in which the compressibility usually comes out too large. Because the derivation starts from a meson-baryon Lagrangian, we are able to show that replacing the meson degrees of freedom by a $\mathrm{NN}$ interaction is a consistent approximation, and the formalism allows one to calculate corrections to this approximation in a well-organized manner. The simplicity of the vacuum in our light-front approach is an important feature in allowing the derivations to proceed. The mesonic Fock space components of the nuclear wave function are obtained also, and aspects of the meson and nucleon plus-momentum distribution functions are computed. We find that there are about 0.05 excess pions per nucleon.

We study the electroproduction transition of the Roper resonance $N^{*}\mathrm{}\left(1440\right)\mathrm{}$ based on a relativistic quark model. The relativistic and meson cloud effects are stressed in this paper. Better agreement for the transverse helicity amplitudes is obtained than with the constituent quark model. A comprehensive understanding of the Roper resonance properties is achieved.

Using modularized NaI(Tl) detectors, we carried out a high-statistics measurement of inclusive ${\pi }^0$ spectra in antiproton annihilation at rest in a liquid $D_2$ target. At the statistical significance above 4σ, we did not see any narrow ${\pi }^0$ peaks due to the production of $B=\mathrm{baryonium}$ or similar narrow states in $\overline{p}\overrightarrow{d}{\pi }^0{\mathrm{BN}}_s$ ($N_s$ being a spectator nucleon) or $\overline{p}\overrightarrow{d}{\pi }^{0}B.\mathrm{}$ The 4σ upper limit for the yields (or branching ratios) per annihilation was $2\times {10}^{-2}–2\times {10}^{-3}$ for the baryonia with a mass ${(M}_B)$ of $1700–1100\mathrm{MeV}{/c}^2$ and a width smaller than 9 (at $M_B\sim 1700\mathrm{MeV}{/c}^2$) to 40 ${(M}_B\sim 1100\mathrm{MeV}{/c}^2)$ $\mathrm{MeV}{/c}^2.$

The ${}^9\mathrm{Be}(p,\gamma {)}^{10}\mathrm{B}$ reaction plays an important role in primordial and stellar nucleosynthesis of light elements in the p shell, but the energy dependence of $S\left(E\right)\mathrm{}$ has not been well understood. We reanalyze the existing ${}^9\mathrm{Be}(p,\gamma {)}^{10}\mathrm{B}$ experimental data within the framework of the R-matrix method. The direct capture part of the S factor is calculated using the experimentally measured asymptotic normalization coefficients for ${}^{10}{\overrightarrow{\mathrm{B}}}^9\mathrm{Be}+p.\mathrm{}$ The fitted parameters of the low-lying ${}^{10}\mathrm{B}$ resonances are also required to be consistent with previous measurements of ${}^6\mathrm{Li}(\alpha ,\gamma {)}^{10}\mathrm{B}.$ A good simultaneous fit to both radiative capture reactions is found, in contrast to previous analyses. These results demonstrate that experimentally measured asymptotic normalization coefficients, coupled to the R-matrix method, can provide a reasonable determination of direct radiative capture rates, even when the captured proton is tightly bound in the final nucleus.

Coincidence spectra from the ${}^7\mathrm{Li}(d,\alpha \alpha )n$ reaction measured for incident energies from 3 to 6 MeV show strong direct contributions for the lower (16.6 MeV) state of the ${}^8\mathrm{Be}$ isospin mixed doublet as well as the interference of these states. We discuss how similar behavior of the mirror $\mathrm{}(d,p)\mathrm{}$ reaction at low energy could affect determination of the total ${}^7\mathrm{Li}{\mathrm{}(d,p)\mathrm{}}^8\mathrm{Li}$ cross section at 0.78 MeV, the quantity often used for normalization in the measurement of the astrophysically important ${}^7\mathrm{Be}(p,\gamma {)}^8\mathrm{B}$ reaction.

A mean-field description of nonoverlaping nucleon bags bound by the self-consistent exchange of $\sigma ,$ $\omega ,$ and $\rho$ mesons is used to investigate the properties of neutron matter at finite temperature. We use the equation of state of zero temperature to study the rotating neutron star in the Komatsu-Eriguchi-Hachisu method. The mass, radius, and angular velocity of the neutron star are calculated and compared with the Walecka model.

In order to improve the description of the N-d vector analyzing powers $A_y$ and ${\mathrm{iT}}_{11}$ (the so-called $A_y$ puzzle) a spin-orbit three-body force has been introduced. The $\mathbf{L}\cdot \mathbf{S}$ term in the $\mathrm{NN}$ potential has been modified including a two-parameter three-body function depending on the hyperradius $\rho$. The modification has been performed in channels where the pair of nucleons $\mathrm{}(i,j)\mathrm{}$ are coupled to spin $S_{\mathrm{ij}}=1\mathrm{}$ and isospin $T_{\mathrm{ij}}=1\mathrm{}$. Calculations have been done in the energy region from $E_{\mathrm{lab}}=648\mathrm{}$ keV up to $E_{\mathrm{lab}}=10\mathrm{}$ MeV. A noticeable improvement in the description of the polarization observables has been obtained.