Detailed sequential decay calculations that include both discrete states and unbound states in the continuum have been performed. Particular attention is paid to the lifetime of continuum states contributing to the process and to the role of the primary charge distribution. Comparisons to the recent data indicate temperatures greater than 7 MeV are model dependent and cannot be determined reliably. Furthermore, correct temperatures must be obtained from isotope yields via careful comparison with sequential decay calculations.

Data on the $\frac{{\pi }^{-}}{{\pi }^{+}}$ ratio in heavy-ion collisions are analyzed by theoretical formula. It accounts for Coulomb interaction between central charged fragment consisting of stopped nucleons with effective charge $Z_{\mathrm{eff}}$ and charged $\pi \text{'}\mathrm{s}$. The Coulomb wave function method is used in order to account for the finite $\pi$ production range $\beta$. For the Gaussian source function it results in a quasiscaling in $\beta$ and $Z_{\mathrm{eff}}$, which makes determination of $\beta$ and $Z_{\mathrm{eff}}$ difficult. Only sufficiently accurate data taken in the extreme small $m_T-m_{\pi }$ region, where this quasiscaling is broken, could be used for this purpose.

In this paper, we present a calculation of the four isospin channels of the kaon photoproduction $\gamma N\to K\Sigma$ in the framework of the chiral quark model. The relative strength and phases in each isospin channel are determined by the quark model wave function with SU(6)⊗O(3) symmetry. The duality hypothesis is imposed to limit the number of the $t$ channel exchanges. The only free parameter, the coupling constant $g_{K\Sigma N}$, is fitted to the total cross section data in $\gamma p\to K^{+}{\Sigma }^0$ channel. We found a remarkable agreement with the data available in the other isospin channels, and it represents a dramatic improvement over the similar calculation in the traditional isobaric model.

First measurements of the longitudinal analyzing power ${\mathit{A}}_{\mathit{z}}$ for noncoplanar p-d breakup at ${\mathit{E}}_{\mathit{p}}$=9 MeV in four kinematically complete configurations are presented. The measurements are compared with Faddeev calculations obtained with the Bonn B nucleon-nucleon interaction and the 2π-exchange Tucson-Melbourne three-nucleon force. The measured analyzing powers and the corresponding theoretical predictions are very small in magnitude and compatible within the error bars of the data. Because of the smallness of ${\mathit{A}}_{\mathit{z}}$, the expected enhanced sensitivity to three-nucleon force effects is not seen in this low energy region. © 1996 The American Physical Society.

Cross-section excitation-energy spectra and angular distributions were measured for the ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(p,n)2p reaction at 135 MeV in 6° steps from 0° to 30° (laboratory), using the beam swinger facility at the Indiana University Cyclotron Facility. The target was a 12.8 mg/${\mathrm{cm}}^2$ foil of ${\mathrm{CD}}_2$. Neutron energies were measured by the time-of-flight method using large-volume plastic scintillator arrays at flight paths of 91 m. The overall energy resolution was 260 keV. The 0° spectrum is dominated by a large peak near 0 MeV of relative energy in the final 2p system; this peak corresponds to the two protons in the ${}_{}{}^1{}_{}{}^{}$${\mathit{S}}_0$ state. The wider-angle spectra are dominated by a broad peak centered at 10 to 20 MeV of excitation which is the quasifree scattering peak. The spectra are compared with impulse approximation and three-body Faddeev calculations. © 1996 The American Physical Society.

The tensor analyzing powers of the ${}_{}{}^1{}_{}{}^{}\mathrm{H}$(d→,γ${)}^3$He reaction are sensitive to the tensor component of the nucleon-nucleon force, which mixes the L=2 D state into the ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ ground state wave function. Modern Faddeev calculations of this reaction allow a quantitative comparison to the parametrization of the tensor force in the trinucleon system. The ${\mathit{T}}_{20}$ analyzing power was measured at an incident beam energy of 5.25 MeV and a laboratory angle of 90° (${\mathrm{\theta }}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=92.9°), where the comparison to theory is especially rigorous. The measured value of ${\mathit{T}}_{20}$(${90}_{\mathrm{lab}}^{\mathrm{°}}$) is -0.035±0.004, which differs by ≊3σ from a recent Faddeev calculation which uses the separable expansion of the Paris potential. © 1996 The American Physical Society.

The four-dimensional NN-πNN equations are adapted to the case of scalar particles with a ${\mathrm{\phi }}^2$σ interaction Lagrangian and solved for energies below the σ-production threshold. This is achieved in the approximation where φσ scattering is dominated by the s-channel φ-pole term. The importance of the removal of double counting is investigated and a detailed comparison of the results of a covariant coupled-channel formulation and the Bethe-Salpeter equation in the ladder and ladder plus crossed-box approximations is presented. A brief discussion of the extension of the method to energies above the σ-production threshold is given. © 1996 The American Physical Society.

We determine the πNN and πNΔ form factors from the ${\mathit{P}}_{11}$ (${\mathit{P}}_{33}$) partial wave of πN scattering by dressing corresponding bare vertices with the help of πN non-s-pole contributions. The underlying model is based on meson exchange, and involves nucleon and delta-isobar pole and crossed-pole terms together with correlated ππ exchange in the ${\mathit{J}}^{\mathit{P}}$=$0^{+}$ (σ) and $1^{\mathrm{-}}$ (ρ) channel. As a whole our results for the πNN form factor are somewhat less soft than (i) those determined recently quite analogously by Saito and Afnan and (ii) our results for the πNΔ form factor. The results for the πNN form factor depend, due to trival kinematical factors, on the type of bare πNN coupling (ps or pv); namely for ps coupling it is less soft. © 1996 The American Physical Society.

We calculate the nucleon-antinucleon static potential in the Skyrme model using the product ansatz and including some finite ${\mathit{N}}_{\mathit{C}}$ (number of colors) corrections. The mid- and long-range part of the spin-spin and tensor force are mostly correctly given in both isospin channels while the central interaction has insufficient midrange attraction. This is a well-known problem of the product ansatz that should be repaired with better Skyrme dynamics. © 1996 The American Physical Society.

A relativistic and manifestly gauge-invariant soft-photon amplitude, which is consistent with the soft-photon theorem and satisfies the Pauli principle, is derived for the proton-proton bremsstrahlung process. This soft-photon amplitude is the first two-u-two-t special amplitude to satisfy all theoretical constraints. The conventional Low amplitude can be obtained as a special case. It is demonstrated that previously proposed amplitudes for this process, both the (u,t) and (s,t) classes, violate the Pauli principle at some level. The origin of the Pauli principle violation is shown to come from two sources: (i) For the (s,t) class, the two-s-two-t amplitude transforms into the two-s-two-u amplitude under the interchange of two initial-state (or final-state) protons. (ii) For the (u,t) class, the use of an internal emission amplitude determined from the gauge-invariance constraint alone, without imposition of the Pauli principle, causes a problem. The resulting internal emission amplitude can depend upon an electromagnetic factor which is not invariant under the interchange of the two protons. © 1996 The American Physical Society.

A search was undertaken to look for evidence of hyperdeformation in ${}_{}{}^{146,147}{}_{}{}^{}\mathrm{Gd}$. Three experiments employing Gammasphere for gamma-ray detection coupled with the Microball for channel selection via charged particle detection were carried out with increasing detection sensitivity and statistics. No definitive evidence for band structures that could be assigned to hyperdeformation could be found. Candidates previously reported are shown not to have properties consistent with a band structure. © 1996 The American Physical Society.

Photodisintegration of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ was accomplished by sending a beam of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$ at 28 MeV/nucleon through the equivalent photon field of a lead target. By measuring the complete kinematics of the disintegration products, ${}_{}{}^9{}_{}{}^{}\mathrm{Li}$+n+n, we constructed the correlation of the angle between the two neutrons in the rest frame of the ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$. The correlation is independent of angle. This result argues against the existence of a bound dineutron in the ground state of ${}_{}{}^{11}{}_{}{}^{}\mathrm{Li}$. © 1996 The American Physical Society.

The β decay of the very-neutron-rich nucleus ${}_{}{}^{103}{}_{}{}^{}\mathrm{Y}$ has been studied at the isotope separator IGISOL, allowing for the first time the observation of nonyrast levels in its daughter ${}_{40}{}^{103}{}_{}{}^{}\mathrm{Zr}_{63}^{}{}_{}{}^{}$. The level structure is similar to that of its isotones ${}_{}{}^{101}{}_{}{}^{}\mathrm{Sr}$ and ${}_{}{}^{105}{}_{}{}^{}\mathrm{Mo}$, suggesting a large ground-state deformation of β≃ 0.4. Level systematics allows for new level assignments in both ${}_{}{}^{103}{}_{}{}^{}\mathrm{Zr}$ and ${}_{}{}^{105}{}_{}{}^{}\mathrm{Mo}$. © 1996 The American Physical Society.

Intruder rotational bands have been investigated to high frequency in ${}_{51}{}^{109}{}_{}{}^{}\mathrm{Sb}$. Five decoupled (ΔI=2) bands extending to rotational frequencies above 1.4 MeV/ħ have been observed. At the highest frequencies, the ${\mathit{J}}^{\mathrm{}\left(2\right)\mathrm{}}$ dynamic moments of inertia for four of these bands are seen to decrease steadily to unexpectedly low values, ${\mathit{J}}^{\mathrm{}\left(2\right)\mathrm{}}$ ∼ 10 ${\mathrm{ħ}}^2$ ${\mathrm{MeV}}^{\mathrm{-}1}$. These four bands, which are interpreted as being based on deformed 2p-2h proton excitations across the Z=50 closed-shell gap, achieve the so-called ‘‘smooth band termination’’ following alignment of the valence nucleons outside of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Sn}$. In addition, two strongly coupled (ΔI=1) bands have been observed, which are related to 1p-1h proton excitations across the gap. © 1996 The American Physical Society.

High-spin states have been populated in the nucleus ${}_{}{}^{149}{}_{}{}^{}\mathrm{Dy}$ using the ${}_{}{}^{122}{}_{}{}^{}\mathrm{Sn}$${(}^{32}$S, 5n${)}^{149}$Dy reaction at a beam energy of 163 MeV. The experimental level scheme has been extended to a spin of 61/2ħ, corresponding to an energy of about 12 MeV, and is adequately explained in the context of the shell model. Most of the levels are characterized by maximally aligned single-particle states with no evidence of collectivity. An alternate shell-model approach has been adopted to assign shell-model configurations. © 1996 The American Physical Society.

The properties of the Be isotopes are studied by the deformed Hartree-Fock method with Skyrme interactions. It is shown for ${}_{}{}^{11}{}_{}{}^{}\mathrm{Be}$ that the configuration where the last neutron occupies a ${\mathit{K}}^{\mathrm{\pi }}$=1/$2^{+}$ orbital is not the ground state but has a matter density distribution with a tail typical of a halo nucleus. Correlations are introduced in deformed mean-field wave functions by a restoration of rotational invariance. These correlations bring the amount of energy necessary to correct the deficiencies of pure mean-field wave functions. © 1996 The American Physical Society.

We introduce an alternative approach to highly correlated systems that generalizes the Fermi hypernetted chain and correlated basis function techniques. While the latter approaches can be applied only to systems for which a nonrelativistic wave function can be defined, the present approach is based on the variation of a trial Hamiltonian within a path-integral framework and thus can be applied also to relativistic and field theoretical problems. We derive a diagrammatic scheme for the present approach and show how a particular choice of trial Hamiltonian corresponds exactly to the use of a Jastrow correlated ansatz for the wave function in the Fermi hypernetted chain approach. We show how our approach can be used to find upper bounds to ground-state energies in systems that the Fermi hypernetted chain approach cannot handle, including those described by an energy-dependent effective Hamiltonian. We demonstrate our approach by applying it to a quantum field theoretical system of interacting pions and nucleons. © 1996 The American Physical Society.

We have performed shell-model calculations for ${}_{}{}^{102,103,104,105}{}_{}{}^{}\mathrm{Sn}$ using two realistic effective interactions derived from the Bonn A and Paris nucleon-nucleon potentials, respectively. From the comparison of the calculated spectra of ${}_{}{}^{104}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{105}{}_{}{}^{}\mathrm{Sn}$ with the experimental ones it turns out that the best agreement is obtained with the weaker tensor force potential (Bonn A). This agreement appears to be significantly better than for other nuclear regions, such as the sd shell, and thus encourages use of modern realistic potentials in shell-model calculations for medium- and heavy-mass nuclei. In addition, it supports confidence in our predictions of the spectra of the hitherto unknown isotopes ${}_{}{}^{102}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{103}{}_{}{}^{}\mathrm{Sn}$. © 1996 The American Physical Society.

The residual part of the realistic forces—obtained after extracting the monopole terms responsible for bulk properties—is strongly dominated by pairing and quadrupole interactions, with important στ⋅στ, octupole, and hexadecapole contributions. Their forms retain the simplicity of the traditional pairing plus multipole models, while eliminating their flaws through a normalization mechanism dictated by a universal ${\mathit{A}}^{\mathrm{-}1/3}$ scaling. Coupling strengths and effective charges are calculated and shown to agree with empirical values. Comparisons between different realistic interactions confirm the claim that they are very similar. © 1996 The American Physical Society.

The yrast spectra, reduced E2 transition matrix elements, and ${\mathit{Q}}_{{\mathit{J}}^{+}}$ values are calculated for the ${}_{}{}^{114}{}_{}{}^{}\mathrm{Ru}$ isotope by carrying out variation-after-projection calculations. The experimentally available spectra up to ${10}^{+}$ is reasonably well reproduced. The yrast spectra up to ${20}^{+}$ and root mean square radii are also obtained in the framework of the cranked-Hartree-Fock-Bogoliubov method. These calculations have been performed by employing a pairing–plus–quadrupole-quadrupole effective interaction operating in a reasonably large valence space outside the ${}_{}{}^{76}{}_{}{}^{}\mathrm{Sr}$ core. Our results indicate that there is a tendency for the nonaxiality to increase as we move along the yrast states. © 1996 The American Physical Society.