The branching ratios for E1 transitions between the spin-dipole (SD) and Gamow-Teller (GT) giant resonances in ${}^{90}\mathrm{Nb}$ and ${}^{208}\mathrm{Pb}$ are evaluated. Assuming the main GT state has a wave function close to that for the “ideal” GT state, we reduced the problem to calculate the SD and GT strength functions. These strength functions are evaluated within an extended continuum-random phase approximation approach.

The ${}^{143}\mathrm{Dy}$ nucleus has been studied with the ${}^{92}\mathrm{Mo}{(}^{54}\mathrm{Fe},$ $2pn\gamma )$ reaction at 240 MeV incident energy. A rich variety of structures was observed at high spin. The nearly spherical $\nu h_{11/2}I=11/2\mathrm{}$ isomer is the basis of a negative parity irregular yrast structure which is observed up to $I=51/2.\mathrm{}$ A positive parity band presenting a large dynamic moment of inertia was observed, similar to the deformation enhanced $\nu i_{13/2}$ bands known to exist in this mass region. However, we propose an alternative assignment for this band, namely the triaxial collective minimum with β=0.2 predicted by total Routhian surface calculations for a $N_{\mathrm{osc}}=4\mathrm{}$ quasineutron excitation coupled to pairs of aligned quasiparticles. Another negative parity structure, with strong $M1\mathrm{}$ and weak $E2\mathrm{}$ crossover transitions, was observed.

Gamma-ray spectra of a 20-h ${}^{255}\mathrm{Fm}$ source containing $\sim 1$ mCi activity were measured with a 25% Ge detector and a low-energy photon spectrometer (LEPS). Gamma lines with intensities as low as $1.0\times {10}^{-6}\%$ per ${}^{255}\mathrm{Fm}$ $\alpha$ decay were observed. Gamma-gamma coincidence spectra of a ${}^{255}\mathrm{Fm}$ sample were measured with the GAMMASPHERE array. A comparison of the $\gamma$-ray spectrum gated by the Cf $K_{\alpha }$ x-ray peak with the $\gamma$-singles spectrum provided spins of the excited states in ${}^{251}\mathrm{Cf}.$ The $\gamma$-ray data, in conjunction with previously measured ${}^{250}\mathrm{Cf}\mathrm{}(d,p)\mathrm{}$ reaction data, allowed us to characterize several single-particle and vibrational states above the $N=152\mathrm{}$ subshell gap.

We examine the photoproduction of the light scalar mesons $f_0$-$a_0\mathrm{}\left(980\right)\mathrm{}$ with emphasis on isospin-violating $f_0$ and $a_0$ mixing due to the mass difference between neutral and charged kaons. General forms for the invariant amplitude for scalar meson photoproduction are derived, which yield expressions for the invariant mass distribution of the final meson pairs. A final state interaction form factor is obtained which incorporates $f_0$ and $a_0$ mesons, $K\overline{K}$ threshold effects, and $f_0$-$a_0$ mixing. This form factor is applied to predict the effective mass distribution of the $\pi \pi$ and $K\overline{K}$ pairs in the vicinity of the $K\overline{K}$ threshold. An estimate of the role of isospin mixing near threshold is provided. The potential role of polarized photons and protons is also discussed.

The expansion velocity profile in central heavy-ion reactions in the Fermi energy domain is examined. The radial expansion is non-Hubblean and in the surface region it scales proportional to a higher exponent $(\alpha >1)$ of the radius. The anomalous expansion velocity profile is accompanied by a power-law nucleon density profile in the surface region. Both these features of central heavy-ion reactions disappear at higher energies, and the system follows a uniform Hubble expansion $\left(\alpha \simeq 1\right).$

The radiative corrections to elastic electron-proton scattering are analyzed in a hadronic model including the finite size of the nucleon. For initial electron energies above 8 GeV and large scattering angles, the proton vertex correction in this model increases by at least 2% of the overall factor by which the one-photon exchange cross section must be multiplied. In addition, we refine the mathematical treatment, removing many of the approximations made in the generally used expressions previously obtained by Mo and Tsai. In particular, the contribution of soft photon emission is calculated exactly. Results are presented for some kinematics at high momentum transfer and compared with the expressions of Mo and Tsai.

We consider the ground state in a model with scalar nucleons and a meson using the formalism of light-front dynamics. Light-front potentials for two-nucleon bound states are calculated using two approaches. First, light-front time-ordered perturbation theory is used to calculate one- and two-meson-exchange potentials. These potentials give results that agree well with the ladder and ladder plus crossed box Bethe-Salpeter spectra. Secondly, approximations that incorporate nonperturbative physics are used to calculate alternative one-meson-exchange potentials. These nonperturbative potentials give better agreement with the spectra of the full nonperturbative ground-state calculation of our restricted model than the perturbative potentials. For lightly bound states, all of the approaches appear to agree with each other.

Properties of the ground and several collective excited states of the light nuclei ${}^{30,32,34}\mathrm{Mg}$ are described in the framework of the angular momentum projected generator coordinate method using the quadrupole moment as collective coordinate and the Gogny force as the effective interaction. The calculated excitation energies and $B\left(E2\mathrm{}\right)\mathrm{}$ transition probabilities agree reasonably well with experiment. The results clearly indicate that both the restoration of the rotational symmetry and the quadrupole dynamics are key ingredients for the description of the properties of the above-mentioned nuclei.

We use (3+1)-dimensional hydrodynamics with exact longitudinal boost invariance to study the influence of collision centrality and initial energy density on the transverse flow pattern and the angular distributions of particles emitted near midrapidity in ultrarelativistic heavy-ion collisions. We concentrate on radial flow and the elliptic flow coefficient $v_2$ as functions of the impact parameter and collision energy. We demonstrate that the finally observed elliptic flow is established earlier in the collision than the observed radial flow and thus probes the equation of state at higher energy densities. We point out that a phase transition from hadronic matter to a color-deconfined quark-gluon plasma leads to nonmonotonic behavior in both beam energy and impact parameter dependences which, if observed, can be used to identify such a phase transition. Our calculations span collision energies from the Brookhaven AGS (Alternating Gradient Synchrotron) to beyond the LHC (Large Hadron Collider); the QGP phase transition signature is predicted between the lowest available SPS (CERN Super Proton Synchrotron) and the highest RHIC (Brookhaven Relativistic Heavy Ion Collider) energies. To optimize the chances for applicability of hydrodynamics we suggest studying the excitation function of flow anisotropies in central uranium-uranium collisions in the side-on-side collision geometry.

Isotopic yields of IMF’s produced in the ${}^{58}\mathrm{Ni}{+}^{12}\mathrm{C}{,}^{24}\mathrm{Mg}$ reactions at $34.5A$ MeV are investigated. Analysis of experimental data from the CRL-Laval $4\pi$ multidetector array focuses on events where at least $75\%$ $\mathrm{}(60\%)\mathrm{}$ of the charge and momentum were detected for the ${}^{58}\mathrm{Ni}{+}^{12}\mathrm{C}$ ${(}^{58}\mathrm{Ni}{+}^{24}\mathrm{Mg})$ system. Averaged isospin ratios $\mathrm{}(N/Z)\mathrm{}$ for IMF’s with $Z=3\mathrm{}$ and 4 are plotted as a function of emission angle and parallel velocity in the center-of-mass frame. Results from simulations with the statistical codes SMM and GEMINI, assuming an equilibrated source, are compared to the experimental ratios. The ratios seem to indicate the presence of a midrapidity necklike structure that would produce IMF’s richer in neutrons than the two main emitters, even for very central collisions.

The differential cross sections for ${\pi }^{-}\overrightarrow{p}\gamma n$ and ${\pi }^{+}\overrightarrow{n}\gamma p$ are computed up to ${O(p}^3)$ in heavy baryon chiral perturbation theory (HBChPT). The expressions at $O\left(p\right)\mathrm{}$ and ${O(p}^2)$ have no free parameters. There are three unknown parameters at ${O(p}^3),$ low energy constants of the HBChPT Lagrangian, which are determined by fitting to experimental data. Two acceptable fits are obtained, which can be separated by comparing with earlier dispersion relation calculations of the inverse process. Expressions for the multipoles, with emphasis on the p-wave multipoles, are obtained and evaluated at threshold. Generally the results obtained from the best of the two fits are in good agreement with the dispersion relation predictions.

We study the questions of the existence and mass of the proposed $d^{\prime }{(IJ}^P{=00\mathrm{}}^{-})$ dibaryon in the quark-delocalization, color-screening model. The transformation between physical and symmetry bases has been extended to the cases beyond the SU(2) orbital symmetry. Using parameters fixed by baryon properties and $\mathrm{NN}$ scattering, we find a mild attraction in the ${\mathrm{IJ}}^P{=00\mathrm{}}^{-}$ channel, but it is not strong enough to form a deeply bound state as proposed for the $d^{\prime }$ state. Nor does the (isospin) $I=2\mathrm{}$ $N\Delta$ configuration have a deeply bound state. These results show that if a narrow dibaryon $d^{\prime }$ state does exist, it must have a more complicated structure.

We have investigated the β decay of the $T=0,$ $T_{1/2}\approx 2.2\mathrm{s},$ isomeric level in the self-conjugate odd-odd nucleus ${}^{70}\mathrm{Br}.$ The observed β-delayed γ rays in the daughter nucleus ${}^{70}\mathrm{Se}$ and the deduced decay properties of the isomeric level allow, in conjunction with results from the deformed shell model, a spin and parity assignment of $J^{\pi }{=9\mathrm{}}^{+}$ and suggest a structure of $\{\pi \left[404\right]{9/2}^{+}\nu \left[404\right]{9/2}^{+}\}{9}^{+}.$ The allowed unhindered β decay of the isomer, possibly oblate deformed, proceeds to four-quasiparticle states in ${}^{70}\mathrm{Se}.$

The formalism of the quasiparticle random phase approximation, extended to include scattering terms in the equation of motion, is used to describe allowed single β-decay transitions of Fermi type at finite temperatures. The calculations were performed by using a realistic single particle basis and a separable two body interaction in the proton-neutron channel. The behavior of the Ikeda sum rule is studied and it is found that this sum rule is strictly conserved in the presence of particle-particle and hole-hole correlations. As an example on the validity of the formalism the case of Fermi transitions in ${}^{76}\mathrm{Ge}$ is considered.

Light charged particles in coincidence with evaporation residues from the ${}^{19}\mathrm{F}{+}^{181}{\overrightarrow{\mathrm{Ta}}}^{200}\mathrm{Pb}$ reaction have been studied at $E_{\mathrm{lab}}=121,$ 154, 179, and 195 MeV with the aim of determining, within the context of the statistical model, a possible dependence of the Fermi-gas level density parameter on the temperature/excitation energy of the emitting system. Angular distributions of evaporation residues and of fission fragments, along with fission fragment folding angle distributions, were also measured. A moderate excitation energy dependence of the level density parameter, as given by recent theoretical calculations, is consistent with the measured $\alpha$-particle spectral shapes. Although the spectra are reproduced best with a weakly varying level density parameter, a constant level density parameter of a=A/12 ${\mathrm{MeV}}^{-1}$ cannot be excluded.

We study the effects of the expansion of the system and the friction on the parametric amplification of mesonic fields in high energy heavy ion collisions within the linear $\sigma$ model. The equation of motion which is similar to the Mathieu equation is derived to describe the time development of the fields in the last stage of a heavy ion collision after the freeze-out time. The enhanced mode is extracted analytically by comparison with the Mathieu equation and the equation of motion is solved numerically to examine whether soft modes will be enhanced or not. It is found that a strong peak appears around 267 MeV in the pion transverse momentum distribution in cases with weak friction and high maximum temperature. This enhancement may be extracted by taking the ratio between different modes in the pion transverse momentum distribution.

The rainbow truncation of the quark Dyson-Schwinger equation is combined with the ladder Bethe-Salpeter equation for the meson amplitudes and the dressed quark-photon vertex in a self-consistent Poincaré-invariant study of the pion and kaon electromagnetic form factors in impulse approximation. We demonstrate explicitly that the current is conserved in this approach and that the obtained results are independent of the momentum partitioning in the Bethe-Salpeter amplitudes. With model gluon parameters previously fixed by the chiral condensate, the pion mass and decay constant, and the kaon mass, the charge radii and spacelike form factors are found to be in good agreement with the experimental data.

We report total cross sections for the ${}^{19}\mathrm{F}(\alpha {,n)}^{22}\mathrm{Na}$ and ${}^{22}\mathrm{Ne}{\mathrm{}(p,n)\mathrm{}}^{22}\mathrm{Na}$ reactions from threshold to 3.1 and 5.4 MeV, respectively. The absolute efficiency of the $4\pi$ neutron detector was determined by Monte Carlo calculations and validated using two standard sources and two nuclear reactions. Cross sections for the inverse reactions (between ground states) have been calculated using the principle of detailed balance, and reaction rates for both the reactions and their inverses determined for temperatures between 0.01 and 10 GK $\mathrm{for}{\hspace{0.5em}}^{19}\mathrm{F}(\alpha {,n)}^{22}\mathrm{Na}$ and between 0.1 and 10 GK for ${}^{22}\mathrm{Ne}{\mathrm{}(p,n)\mathrm{}}^{22}\mathrm{Na}.$

We calculate the longitudinal response of ${}^{208}\mathrm{Pb}$ using a relativistic random-phase approximation to three different parametrizations of the Walecka model with scalar self-interactions. From a nonspectral calculation of the response—which automatically includes the mixing between positive- and negative-energy states—we extract the distribution of strength for the isoscalar monopole, dipole, and high-energy octupole resonances. We employ a consistent formalism that uses the same interaction in the calculation of the ground state as in the calculation of the response. As a result, the conservation of the vector current is strictly maintained throughout the calculation. Further, the spurious dipole strength—associated with the uniform translation of the center of mass—gets shifted to zero excitation energy and is cleanly separated from the physical excitations. The best description of the collective modes is obtained using a “soft” parametrization having a compression modulus of $K=224\mathrm{}\hspace{0.5em}\mathrm{MeV}$.