Photons have long been considered as a probe of the dynamics of high energy nuclear collisions. Here we present simple analytical expressions which parametrize the thermal production rates of photons for the processes ππ→ργ, πρ→πγ, and ρ→ππγ which are occuring in hot mesonic matter. These parametrizations are good for photon energies greater than 150 MeV and for temperatures between 100 and 200 MeV. They can be used in various thermal and hydrodynamical models of heavy ion collisions.

The rotational alignment of ${\mathit{h}}_{11/2}$ neutrons is considerably delayed (Δħω∼0.11 MeV) in the π${\mathit{h}}_{11/2}$[550]1/$2^{\mathrm{-}}$ intruder band in ${}_{}{}^{117}{}_{}{}^{}\mathrm{I}$ when compared to bands built on normal-parity states. Comparison with cranked shell-model calculations suggests that this effect may indicate a larger quadrupole deformation for the intruder orbital. A strong neutron-proton interaction between the aligning ${\mathit{h}}_{11/2}$ neutrons and the ${\mathit{h}}_{11/2}$ proton intruder may also play a role. In addition, noncollective oblate states at ${\mathit{I}}^{\mathrm{\pi }}$=39/$2^{\mathrm{-}}$,43/$2^{\mathrm{-}}$, and 45/$2^{\mathrm{-}}$ compete energetically with rotational states of the intruder band which may also perturb the neutron alignment.

Analyzing power measurements are presented for radiative capture of polarized protons on deuterium and for polarized deuterons on hydrogen at ${\mathit{E}}_{\mathrm{c}.\mathrm{m}.\mathrm{}}$=3.33 MeV. The reaction is dominated by E1 capture from channel-spin ${\mathit{S}}_{\mathit{c}}$=1/2 states; however, the measurements show clear evidence of M1, E2, and spin-flip (${\mathit{S}}_{\mathit{c}}$=3/2) E1 contributions at the 1/2% level. The new data can impose fairly strong constraints on individual matrix elements.

Nuclear multifragmentation processes may show features such as intermittency that signal scale-invariant properties of fluctuations in the fragment distributions. We test this behavior using several models and show that intermittency may be caused by a combination of finite-size effects and the mixing of fragmentation events corresponding to different initial conditions.

Energy staggering in octupole bands in deformed nuclei is studied. The data show dramatic variations, even reversals, and a singularity in the staggering, across the rare-earth region. A simple model analysis, which is almost parameter independent, is able to reproduce the phenomenology, including the discontinuity, and is amenable to a simple physical interpretation.

The thermonuclear burning rates for the ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(α,γ${)}^{18}$O radiative capture reaction are calculated at temperatures (0.3<T<10 GK) of relevance to the early universe. These rates are particularly important for estimating the formation of heavy elements in an inhomogeneous big bang nucleosynthesis, proposed by Applegate, Hogan, and Scherrer (that would suggest the quark-gluon to hadron phase transition is first order). We investigate the effect of a possible new broad (Γ≊0.45 MeV) $1^{\mathrm{-}}$ state, at approximately 9.0 MeV in ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ as would be deduced from the Yale-Michigan State University measurement of the beta-delayed alpha-particle emission of ${}_{}{}^{18}{}_{}{}^{}\mathrm{N}$ and suggested by the Notre Dame-Caltech measurement of the nonresonant ${}_{}{}^{14}{}_{}{}^{}\mathrm{C}$(α,γ${)}^{18}$O cross section. The gamma widths of the proposed broad state is estimated using the Alhassid, Gai, and Bertsch sum rule, and an experimental study is proposed.

By using Bjorken’s hydrodynamical model, we show that a dynamical freeze-out criterion leads to an energy-decreasing dissociation temperature.

The effect of distortion in quasifree excitation in the charge exchange reaction ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(d→,2p${[}^1$${\mathit{S}}_0$]) at 1.6 GeV bombarding energy is evaluated in the eikonal limit. When taking into account the effect of distortion for the two probe particles individually, the experimentally observed enhancement of the spin-transverse over the spin-longitudinal cross section is qualitatively explained.

Particle emission from different shells after electroexcitation of a nucleus is studied in the quasielastic region of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(e,e’p${)}^{11}$B reaction. The rescattering processes and in particular the coupling between (e,e’p) and (e,e’n) channels show a sizable density dependence. The resulting shell dependence of the longitudinal/transverse suppression, using the free nucleon form factors, is close to the one observed in the experimental data.

Energetic photon production cross sections in proton-deuteron reactions at intermediate proton incident energies are calculated by using a meson-exchange potential model for describing the elementary nucleon-nucleon bremsstrahlung amplitude. The convection, magnetization, and exchange current contributions as well as the kinematics prescribed by the momentum distribution of the deuteron are included explicitly. The results are compared with the recent data of the Grenoble and Michigan State groups. The absolute cross sections are consistently underpredicted by ∼(20–40)% which indicates that further work is required for a better understanding of the elementary pn bremsstrahlung process.

The Argonne Δ model is used to study the effect of one-Δ and ΔΔ degrees of freedom on the triton binding energy (${\mathit{E}}_{\mathit{T}}$). Exploratory calculations decompose the J≤4 system of interest into restricted (JL2) calculations, with J≤2 and L(NΔ), L(ΔΔ)≤2, and a 130 keV attractive correction. A JL2 dispersive calculation yields ${\mathit{E}}_{\mathit{T}}$=6.50 MeV, while a full JL2 calculation gives 7.16 MeV, revealing an attractive Δ three-body-force (3BF) contribution of 660 keV. Comparing to the nucleons-only value, ${\mathit{E}}_{\mathit{T}}$=7.58 MeV, the size of the repulsive Δ dispersive effect is 1080 keV. The one-Δ and ΔΔ 3BF contributions are found to be 440 and 220 keV, respectively, while the corresponding full J≤4 values are 450 and 290 keV, respectively. The net J≤4 result is ${\mathit{E}}_{\mathit{T}}$=7.29 MeV versus a nucleons-only value of 7.67 MeV: the attractive Δ 3BF contribution is not quite sufficient to cancel the 1120 keV repulsive Δ dispersive effect. The cancellation between dispersive and 3BF effects is similar to that found for the Hannover Δ model, although the residual Δ repulsive effect found for the Argonne model is non-negligible: Δ effects are found not to resolve the triton binding energy defect. It is also evident from these results that Δ dispersive effects are not adequately represented in nucleons-only models simply by force of fitting the NN data. Thus, the present results confirm the qualitative implications of our previous studies using the Hannover Δ model, including the fact that ΔΔ effects are appreciable.

We calculate an energy-independent nucleon-nucleon potential using the folded-diagram expansion following closely the philosophy for selecting one- and two-meson-exchange terms that led to the successful Bonn energy-dependent interaction. Coupling parameters are very similar in the two cases, as is the reproduction of the scattering phase shifts and deuteron properties, including the electromagnetic form factors. We also present a simpler one-meson-exchange folded-diagram potential. We study the properties of the many-body system using the two energy-independent interactions. The triton is underbound by about 1 MeV, and nuclear matter underbinds at a saturation density considerably above the empirical density, suggesting the need for intrinsic three-body forces. These are considerably different from the properties attributed to the energy-dependent Bonn interactions, reflecting our earlier observation that numerous higher-order corrections need to be considered in the energy-dependent scheme to obtain comparable many-body results.

The apparent discrepancy between the ${\mathit{K}}^{\mathrm{-}}$p scattering length obtained from the 1S level shift of the kaonic hydrogen atom and that from the K¯N scattering at low energies is reexamined. Two models, one proposed by Kumar and Nogami and the other by Schnick and Landau, are extended by including all relevant channels so that comparison with all data available at low energies is possible. A value of the ${\mathit{K}}^{\mathrm{-}}$p scattering length consistent with the atomic data and a good overall fit to all the other low energy data have been obtained by means of the extended Schnick-Landau model. The resulting ${\mathit{K}}^{\mathrm{-}}$p scattering amplitude is quite different from the one determined earlier by means of the K-matrix parametrization. Its sign around threshold is opposite to that indicated by the low energy extrapolation of the Coulomb-nuclear interference data. It is argued that the extrapolation is subject to some uncertainty.

We develop a nonperturbative method for obtaining pion dressing for strong interaction through minimization of total energy. As an illustration, using coherent states we consider the pion-nucleon system with the physical nucleon represented by the bare nucleon and a calculable meson cloud. We next extend the method to obtain pion dressing for the two nucleon system with deuteron as an example. The analysis de facto replaces the scalar-isoscalar potential in nuclear physics by multipion condensates and yields approximately correct results.

Nucleon-nucleon data below 300-MeV laboratory energy are described by a manifestly covariant wave equation in which one of the intermediate nucleons is restricted to its mass shell. Antisymmetrization of the kernel yields an equation in which the two nucleons are treated in an exactly symmetric manner, and in which all amplitudes satisfy the Pauli principle exactly. The kernel is modeled by the sum of one boson exchanges, and four models, all of which fit the data very well (${\mathrm{\chi }}^2$≃3 per data point) are discussed. Two models require the exchange of only the π, σ, ρ, and ω, but also require an admixture of ${\gamma }^5$ coupling for the pion, while two other models restrict the pion coupling to pure ${\gamma }^5$${\gamma }^{\mathrm{\mu }}$, but require the exchange of six mesons, including the η, and a light scalar-isovector meson referred to as ${\mathrm{\sigma }}_1$. Deuteron wave functions resulting from these models are obtained. The singularities and relativistic effects which are a part of this approach are discussed, and a complete development of the theory is presented.

Bethe-Salpeter equations for two and three particles are employed to study relativistic effects in the three-nucleon bound-state system. The used covariant, multirank separable interactions are constructed from one phenomenological (Graz II) and two different meson-exchange potentials (Paris and Bonn). The obtained increase in the triton binding energy due to relativity ranges from 0.29 to 0.38 MeV. In an approximation where boost effects are neglected and an angular-averaging procedure is applied in the construction of the total trinucleon wave function, the elastic charge form factors are calculated.

Weak levels in the compound nucleus ${}_{}{}^{114}{}_{}{}^{}\mathrm{Cd}$ were located by neutron time-of-flight spectroscopy techniques. Neutron capture measurements were performed with both a natural cadmium target and a highly enriched ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cd}$ target. A total of 22 new resonances were located in the neutron energy interval 20-500 eV and were assumed to be p-wave. Resonance parameters, ${\mathit{E}}_0$ and g${\mathrm{\Gamma }}_{\mathit{n}}$, are given for the newly identified levels. The p-wave strength function was determined to be ${10}^4$${\mathit{S}}_1$=2.8±0.8 and the average level spacing 〈${\mathit{D}}_1$〉=14 eV. Comparison of the reduced widths with a Porter-Thomas distribution is consistent with having missed 15% of the p-wave levels.

Resonances in the reaction ${}_{}{}^{48}{}_{}{}^{}\mathrm{Ti}$(p,γ${)}^{49}$V from 1.75 to 2.50 MeV have been observed with a resolution of 2 keV. Spins of 58 resonances are inferred from their γ-decay schemes, both by considering known final-state spins and by comparing branching patterns to those from resonances of known spin using multidimensional scaling. Limits to possible spins of 29 bound states, some observed here for the first time in γ spectra, are proposed. In the energy range studied, there are eleven ${}_{}{}^{49}{}_{}{}^{}\mathrm{Ti}$ levels of spin <9/2. Of the eight previously proposed analogs, two have directly measured spins. Among the remaining six, three appear to have spins incompatible with their parents. Three new analog candidates are proposed, along with new fragments of existing analogs.

High spin states in ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ and ${}_{}{}^{90}{}_{}{}^{}\mathrm{Mo}$ have been studied using the reactions ${}_{}{}^{59}{}_{}{}^{}\mathrm{Co}$${(}^{37}$Cl,2p2n${)}^{92}$Mo, ${}_{}{}^{66}{}_{}{}^{}\mathrm{Zn}$${(}^{30}$Si,2p2n${)}^{92}$Mo, and ${}_{}{}^{66}{}_{}{}^{}\mathrm{Zn}$${(}^{28}$Si,2p2n${)}^{90}$Mo at beam energies 90–120 MeV. Level energies, spins, and parities have been established up to spin 17ħ (${\mathit{E}}_{\mathit{x}}$=8–9 MeV) on the basis of gamma-gamma coincidence and angular distribution measurements. All the states in these two nuclei could be described by spherical shell-model calculations.