This paper represents a continuation of our earlier report on the measurement of the reaction ${}^1\mathrm{H}(\gamma ,{\pi }^0)$ in the threshold region (144.7–169.3 MeV). More specifically, we present pion angular distributions reconstructed using information on the ${\pi }^0$-decay photon energies not previously utilized. Analysis of these distributions reconfirms most of our previous conclusions. In particular, we confirm the rapid increase in the real part of the $S$-wave multipole, $\mathrm{Re}{E}_{0+},$ at energies above the ${\pi }^{+}$ threshold. New results for the $P$-wave amplitude $P_1$ are presented.

The chiral constituent quark model is applied to predict the magnetic $M1\mathrm{}$ and electric $E2\mathrm{}$ amplitudes of the $\Delta \leftrightarrow \gamma N$ transition. It is found that the one-meson-exchange quark-quark potential due to the chiral fields enhances the $E2/M1\mathrm{}$ ratio by a factor of about 2. The predicted $M_{1^{+}}$ amplitude and the $E2/M1\mathrm{}$ ratio $\simeq -1.0\%$ are within the range determined from a recent analysis of the data of pion photoproduction.

A hybrid model for baryons based on a dynamical interplay between relativistic three-quark bound states and soliton configurations of mesons is constructed. The Bethe-Salpeter equation for diquarks and the Faddeev equation for diquark-quark bound states in the background of a soliton are solved. The results show that baryons are very much like hybrids containing both solitonic meson clouds and three-quark correlations.

The $\rho$-meson electromagnetic form factors are calculated, both in covariant and light-front frameworks with constituent quarks. The effect of the breakdown of rotational symmetry for the one-body current operator in the null plane is investigated by comparing calculations within light-front and covariant approaches. This allows to choose the appropriate light-front prescription, among the several ones, to best evaluate the $\rho$-meson form factors.

Recent measurements of spin-rotation parameters in elastic ${\pi }^{+}p$ scattering are in marked disagreement with predictions of the Carnegie-Mellon$-$Berkeley and Karlsruhe-Helsinki analyses. Using the method of Barrelet, we show how this discrepancy can be removed. We then show how this Barrelet transformation alters the partial-wave amplitudes. The effect of unitarity and analyticity constraints is also considered.

The number and type of measurements needed to ascertain the amplitudes for pseudoscalar meson photoproduction are analyzed in this paper. It is found that eight carefully selected measurements can determine the four transversity amplitudes without discrete ambiguities. That number of measurements is one less than previously believed. We approach this problem in two distinct ways: (1) solving for the amplitude magnitudes and phases directly, and (2) using a bilinear helicity product formulation to map an algebra of measurements over to the well-known algebra of the $4\times 4$ gamma matrices. It is shown that the latter method leads to an alternate proof that eight carefully chosen experiments suffice for determining the transversity amplitudes completely. In addition, Fierz transformations of the gamma matrices are used to develop useful linear and nonlinear relationships between the spin observables. These relationships not only help in finding complete sets of experiments, but also yield important constraints between the 16 observables for this reaction.

The chromodielectric soliton model is Lorentz and chirally invariant. It has been demonstrated to exhibit dynamical chiral symmetry breaking and spatial confinement in the locally uniform approximation. We here study the full nonlocal quark self-energy in a color-dielectric medium modeled by a two-parameter Fermi function. Here color confinement is manifest. The self-energy thus obtained is used to calculate quark wave functions in the medium which, in turn, are used to calculate the nucleon and pion masses in the one-gluon-exchange approximation. The nucleon mass is fixed to its empirical value using scaling arguments; the pion mass (for massless current quarks) turns out to be small but nonzero, depending on the model parameters.

Charged current reactions of ${\nu }_e$ on ${}^{12}$C have been studied using a ${\mu }^{+}$ decay-at-rest ${\nu }_e$ beam from the Los Alamos Meson Physics Facility. More than 500 events from the exclusive reaction ${}^{12}\mathrm{C}({\nu }_e{,e}^{-}{)}^{12}{\mathrm{N}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ were measured in a large Liquid Scintillator Neutrino Detector (LSND). The observed energy dependence of the cross section and the angular distribution of the outgoing electron agree well with theoretical expectations. Measurements are also presented for inclusive transitions to ${}^{12}\mathrm{N}$ excited states, ${}^{12}\mathrm{C}({\nu }_e{,e}^{-}{)}^{12}{\mathrm{N}}^{*}$ and compared with theoretical expectations. Results are consistent with a recent continuum random phase approximation (CRPA) calculation.

We study the properties of nuclei in the inner crusts of neutron stars based on the Boguta-Bodmer nonlinear model in the relativistic mean-field theory. We carefully determine the surface diffuseness of the nuclei as the density of matter increases. The imaginary time step method is used to solve the Euler-Lagrange equation derived from the variational principle applied to the semiclassical energy density. It is shown that with increasing density, the spherical nuclei become more neutron rich and eventually merge to form a uniform liquid of neutrons, protons, and electrons. We find that the smaller the value of the incompressibility $K$, the lower the density at which the phase transition to uniform matter occurs. The relativistic extended Thomas-Fermi method is generalized to investigate nonspherical nuclei. Our results show that the spherical nucleus phase is the only equilibrium state in the inner crusts of neutron stars.

High-resolution ${(e,e}^{\prime })$ and ${(p,p}^{\prime })$ spectra for the isoscalar giant quadrupole resonance in ${}^{208}$Pb are presented. Fine structure that has been observed hitherto in ${(e,e}^{\prime })$ is now also seen in ${(p,p}^{\prime })$ and found to be very similar in both experiments. Comparison with results from model calculations reveals the coupling of the random phase approximation modes to surface vibrations as a main source of this fine structure.

Lifetimes of low-lying levels in the one- and three-quasiparticle bands in ${}^{133}$Ce have been measured using the recoil-distance Doppler-shift technique. The $E2\mathrm{}$ transition strengths extracted for the negative parity yrast states are well described by the triaxial-rotor-plus-quasiparticle and the geometrical models, but the interacting-boson-plus-fermion predictions are too small by about a factor of 3. The $B\left(M1\mathrm{}\right)\mathrm{}$ values extracted for the levels in the positive parity three-quasiparticle band are consistent with the previous $\nu h_{11/2}\otimes \pi h_{11/2}\otimes \pi g_{7/2}$ configuration assignment to this band.

The creation of a clustered and neutron-rich midvelocity (“neck” or “hot spot”) region in intermediate-energy heavy-ion collisions is discussed. Reaction simulations suggest that the preponderance of the neutron-rich species in isotopic and isobaric ratios results primarily from the amplification of the initial neutron excess due to $d$ (and by inference $\alpha$-particle) cluster formation.

We investigate sub-barrier fusion phenomena in the presence of triaxial static deformations and under conditions of $\gamma$ instability. It is found that the distributions of effective barriers can reflect in a distinct way a general quadrupole profile specified in terms of both ${\beta }_2$ and $\gamma$. Fusion cross sections as a function of energy are, on the other hand, rather insensitive to the $\gamma$ degree of freedom.

The total cross section for the $\gamma n\to p{\pi }^{-}{\pi }^0$ reaction has been measured over the photon energy range 450–800 MeV at the 855 MeV MAMI Microtron in Mainz with the large acceptance detector DAPHNE and using a deuterium target. As expected, this reaction has a very similar cross section to the $\gamma p\to n{\pi }^{+}{\pi }^0$ channel and its amplitude is strongly underestimated by the existing double pion photoproduction models.

Proton radioactivities from ${}^{157}\mathrm{Ta}$ and ${}^{161}\mathrm{Re}$ are reported. Fusion-evaporation residues from the reaction of 270 MeV ${}^{58}\mathrm{Ni}$ ions on ${}^{102}\mathrm{Pd}$ and ${}^{106}\mathrm{Cd}$ targets were separated according to $M/Q$ and implanted into a double-sided silicon strip detector. One line from ${}^{157}\mathrm{Ta}$ was observed with a proton energy of 927(7) keV [$t_{1/2}=10.1\mathrm{}\left(4\right)\mathrm{}$ ms, $b_p=3.4\mathrm{}\left(12\right)\mathrm{}$%] from the $\pi s_{1/2}$ ground state. A new alpha decay transition with energy 6117(4) keV was also observed from this state. Two proton lines from ${}^{161}\mathrm{Re}$ were observed with energies 1192(6) keV $[t_{1/2}=0.37\mathrm{}(4)\mathrm{}$ ms, $b_p=100\mathrm{}\left(7\right)\mathrm{}$%] and 1315(7) keV $[t_{1/2}=16\mathrm{}(1)\mathrm{}$ ms, $b_p=4.8\mathrm{}\left(6\right)\mathrm{}$%] from the $\pi s_{1/2}$ and $\pi h_{11/2}$ states, respectively.

Lifetimes of the 14${}^{+}$, 12${}^{+}$, 10${}^{+}$ states and, for the first time, the 8${}^{+}$ state in the yrast superdeformed (SD) band of ${}^{194}$Pb were measured at Gammasphere with the recoil-distance Doppler-shift method. Constant transition quadrupole moments with an average of 18.8 (11) $e$b were found at the bottom of the SD band. The decay out of the SD band can be viewed as governed by a small admixture of normal deformed (ND) states to the SD wave function which is assessed for the 8${}^{+}$ and 10${}^{+}$ SD states based on a simple mixing model. The electromagnetic properties of the ND states involved in the decay out are extracted for the first time by investigating the decay strength of the discrete linking transitions. Despite the large intensity of observed linking transitions, the new data show that the decay out of the SD band is statistical in nature.

The effects of an interplay of radial expansion of the thermalized system created in a heavy ion collision and directed flow are discussed. It is shown that the study of azimuthal anisotropy of particle distribution as a function of rapidity and transverse momentum could reveal important information on both radial and directed flow.

It is shown that differences, due to charge-dependent effects, in the ${}^{17}$N and ${}^{17}$Ne ground-state wave functions account for the fact that the experimentally measured branch for the ${\beta }^{+}$ decay of ${}^{17}$Ne to the first excited state of ${}^{17}$F is roughly a factor of two larger than expected on the basis of nuclear matrix elements which reproduce the corresponding ${\beta }^{-}$ branch in the decay of ${}^{17}$N.

It is pointed out that the generalized Bethe formula for the total level density encompasses the standard Bethe formula and the constant temperature formula as limiting cases. It is shown that the generalized Bethe formula provides an excellent fit to the results of combinatorial calculations in the region of doubly closed shell nucleus ${}^{208}\mathrm{Pb}$ where the standard Bethe formula fails. The new parameter $\xi$ associated with the generalized Bethe formula shows a systematic behavior with distance from double shell closure.

In a finite temperature Thomas-Fermi theory with realistic nuclear interactions, we construct caloric curves for finite nuclei enclosed in a sphere of about 4 to 8 times the normal nuclear volume. The specific heat capacity $C_v$ shows a peaked structure that is possibly indicative of a liquid-gas phase transition in finite nuclear systems.