Pion elastic, charge exchange scattering, and induced eta production on the trinucleon systems are investigated in a coupled-channels approach in momentum space with Faddeev wave functions. The channel πN→ηN is included using an isobar model with S-, P-, and D-wave resonances. While the coherent reactions like ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(π,π${)}^3$He can be reasonably well reproduced up to ${\mathit{T}}_{\mathrm{\pi }}$=500 MeV, large discrepancies appear for the incoherent processes ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^0$${)}^3$H and ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(${\mathrm{\pi }}^{\mathrm{-}}$,η${)}^3$H at backward angles and energies above Δ resonance. In the forward direction, the (π,η) calculations underestimate the experimental measurements very close to threshold, but agreement with the data improves with increasing pion energy. Predictions are made for the asymmetries of the various reactions on polarized ${}_{}{}^3{}_{}{}^{}\mathrm{He}$.

The inelastic reactions ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(${\mathrm{\pi }}^{+}$,${\mathrm{\pi }}^{+}$)X, ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(${\mathrm{\pi }}^{\mathrm{-}}$,${\mathrm{\pi }}^0$)X, ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(${\mathrm{\pi }}^{+}$,p)X, and ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(${\mathrm{\pi }}^{\mathrm{-}}$,p)X are studied within a relativistic three-body model. Single and double differential cross sections are calculated and compared with available data and predictions are made where no data exist. Several approximate theoretical prescriptions are compared with the full calculation as well as the results from two different deuteron wave functions.

A modified Low procedure for constructing soft-photon amplitudes has been used to derive two general soft-photon amplitudes, a two-s–two-t special amplitude ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}$ and a two-u–two-t special amplitude ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$, where s, t, and u are the Mandelstam variables. ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}$ depends only on the elastic T matrix evaluated at four sets of (s,t) fixed by the requirement that the amplitude be free of derivatives (∂T/∂s and/or ∂T/∂t). Likewise ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$ depends only on the elastic T matrix evaluated at four sets of (u,t) also fixed by the requirement that the amplitude ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$ be free of derivatives (∂T/∂u and/or ∂T/∂t). In deriving these two amplitudes, we imposed the condition that ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}$ and ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$ reduce to M${\mathrm{¯}}_{\mathrm{\mu }}^{\mathit{T}\mathit{sTts}}$ and M${\mathrm{¯}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$, respectively, their tree-level approximations.

The amplitude M${\mathrm{¯}}_{\mathrm{\mu }}^{\mathit{TsTts}}$ represents photon emission from a sum of one-particle t-channel exchange diagrams and one-particle s-channel exchange diagrams, while the amplitude M${\mathrm{¯}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$ represents photon emission from a sum of one-particle t-channel exchange diagrams and one-particle u-channel exchange diagrams. The precise expressions for M¯ ${}_{\mathrm{\mu }}{}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}{}_{}{}^{}$ and M${\mathrm{¯}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$ are determined by using the radiation decomposition identities of Brodsky and Brown. We also demonstrate that two Low amplitudes ${\mathit{M}}_{\mathrm{\mu }}^{\mathrm{L}\mathrm{o}\mathrm{w}\left(\mathit{s}\mathit{t}\right)}$ and ${\mathit{M}}_{\mathrm{\mu }}^{\mathrm{L}\mathrm{o}\mathrm{w}\left(\mathit{u}\mathit{t}\right)}$, derived using Low’s standard procedure, can be obtained from ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}$ and ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$, respectively, as an expansion in powers of K (photon energy) when terms of order K and higher are neglected. We point out that it is theoretically impossible to describe all nuclear bremsstrahlung processes by using only a single class of soft-photon amplitudes. At least two different classes are required: the amplutides (such as ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}$, ${\mathit{M}}_{\mathrm{\mu }}^{\mathrm{L}\mathrm{o}\mathrm{w}\left(\mathit{s}\mathit{t}\right)}$, and M${\mathrm{¯}}_{\mathrm{\mu }}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}$), which depend on s and t, and the amplitudes (such as ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$, ${\mathit{M}}_{\mathrm{\mu }}^{\mathrm{L}\mathrm{o}\mathrm{w}\left(\mathit{u}\mathit{t}\right)}$, and M${\mathrm{¯}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$), which depend on u and t. When resonance effects are important, the amplitude ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{s}\mathit{T}\mathit{t}\mathit{s}}$, not ${\mathit{M}}_{\mathrm{\mu }}^{\mathrm{L}\mathrm{o}\mathrm{w}\left(\mathit{s}\mathit{t}\right)}$, should be used. For processes with strong u-channel exchange effects, the amplitude ${\mathit{M}}_{\mathrm{\mu }}^{\mathit{T}\mathit{u}\mathit{T}\mathit{t}\mathit{s}}$ should be the first choice. As for those processes which exhibit neither resonance effects nor u-channel exchange effects, all amplitudes converge essentially to the same description. Finally, we discuss the relationship between the two classes.

Variants of a one-boson-exchange potential are applied to elastic nucleon-deuteron and electron-deuteron scattering. The models differ with respect to the treatment of the pion-nucleon vertex, where either a small coupling constant or a soft form factor is employed. We find that these variations do not affect Nd observables, but that they have a sizable effect on ed quantities via exchange currents of the pion. Taking into account also exchange currents of the π’ reduces the effect to a large extent.

The inverted ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${(}^{68}$Zn,2n) reaction was used to populate states in ${}_{}{}^{78}{}_{}{}^{}\mathrm{Kr}$ in the region of the first alignment of the yrast band at ħω=0.56 MeV. The precessions of these states in the transient magnetic field of an ${}_{}{}^{54}{}_{}{}^{}\mathrm{Fe}$ foil were measured to determine the nature of the alignment. The relatively small precession angle of the $8^{+}$ state indicates that the aligning nucleons at the first crossing are neutrons. This is contrary to expectations based on the systematics in this region, and it suggests this shape-coexistent nucleus has an oblate shape throughout the ground state band.

We present the total photonuclear cross section for Be and C measured between 200 and 1100 MeV, with the aim of clarifying the existence of a resonant behavior in the region above the Δ. We used a tagged photon beam and the transmission technique. The results show no evidence of baryon resonances that are clearly seen at ≊700 and ≊1000 MeV in photon absorption on the proton and the deuteron.

The transition from strong static pairing to weak static pairing and its consequences to the excitation spectrum of a mesoscopic (medium number of particles) system are investigated. New levels have been measured in ${}_{}{}^{168}{}_{}{}^{}\mathrm{Yb}$. A reasonable description of the A≊168 isotopes spectra is obtained. The adequacy of the phase transition concept is discussed.

The nucleus ${}_{}{}^{193}{}_{}{}^{}\mathrm{Hg}$ was populated in the reaction ${}_{}{}^{176}{}_{}{}^{}\mathrm{Yb}$${(}^{22}$Ne,5n) at the incident energy E${(}^{22}$Ne)=110 MeV. Reaction γ rays were detected with a Ge-detector array. A new ‘‘collective’’ structure was observed at ${\mathit{E}}_{\mathit{x}}$>5.7 MeV. The states of the structure extend from I≥47/2 to I+10, and they decay with competing dipole and quadrupole transitions. The structure is populated very strongly in this reaction: the lowest member is produced with ∼20% of the ${}_{}{}^{193}{}_{}{}^{}\mathrm{Hg}$ cross section.

The disappearance of collective flow effects in heavy ion collisions is investigated using a microscopic optical model formalism for estimating collision momentum transfers. Phenomenological expressions for the balance energy are obtained which agree very well with measurements for various experimental collision pairs and with results obtained from Boltzmann-Uehling-Uhlenbeck simulations.

It is shown that the striking energy variation in the pd${\to }^3$He η cross section near threshold is probably due to a final state interaction associated with a large (complex) η${\mathrm{-}}^3$He scattering length. The consequences of this hypothesis are studied for the production of the meson in the η${\mathrm{-}}^4$He and η${\mathrm{-}}^7$Be channels.

The three-body photodisintegration of ${}_{}{}^3{}_{}{}^{}\mathrm{He}$ has been measured at photon energies ranging from 90 to 250 MeV, in kinematic regions where three-body forces effects are expected to be maximized, and two-body mechanisms suppressed. The differential cross sections as a function of neutron momentum demonstrate that calculations using only one-body and two-body photoabsorption mechanisms cannot describe the data and that a two-pion-exchange, three-body absorption mechanism is needed to adequately describe the data.

A kinematically complete measurement of the four-body breakup reaction d+d→${\mathit{d}}^{\mathrm{*}}$+${\mathit{d}}^{\mathrm{*}}$→p+n+p+n has been performed at 15.7 MeV bombarding energy. A ring-detector system consisting of a charged-particle detector and a neutron detector is used to define a singlet deuteron, i.e., ${\mathit{d}}^{\mathrm{*}}$; a charged-particle detector is used to measure spectra of products produced by another ${\mathit{d}}^{\mathrm{*}}$ at five angles. A velocity-distribution diagram has first been obtained, and by performing a fit the most probable breakup energy of the singlet deuteron in the laboratory system is obtained, 0.054±0.012 MeV. A final state interaction calculation using known p-n singlet phase shifts predicts the expected proton spectra.

Two values for the asymptotic D/S ratio of the deuteron η=0.27 01±0.000 19 and η=0.027 13±0.000 06 are obtained using two empirical linear ${\mathrm{\epsilon }}_{1\mathrm{-}}$Q and η-${\gamma }^2$Q relations we found for standard nonrelativistic potential models. It is shown that fitting the deuteron quadrupole moment Q, the deuteron rms matter radius ${\mathit{r}}_{\mathit{d}}$, and the triplet scattering length ${\mathit{a}}_{\mathit{t}}$ simultaneously by a nonrelativistic nucleon-nucleon potential model is a critical task and it has been achieved by the inclusion of a short-range attractive nonlocality in the potential.

The two-nucleon phase shifts and deuteron properties are fitted using relativistic, (${\mathit{m}}^2$+${\mathit{p}}^2$${)}^{1/2}$, kinetic-energy operators to obtain realistic models of v${\mathrm{̃}}_{\mathit{i}\mathit{j}}$, the two-nucleon interaction in the frame in which the total momentum ${\mathbf{P}}_{\mathit{i}\mathit{j}}$ of the interacting pair is zero. The relativistic Hamiltonian ${\mathit{H}}_{\mathit{R}}$ contains the relativistic kinetic energy, v${\mathrm{̃}}_{\mathit{i}\mathit{j}}$, and δ${\mathit{v}}_{\mathit{i}\mathit{j}}$(${\mathbf{P}}_{\mathit{i}\mathit{j}}$) which describes the dependence of the interaction on the total momentum of the pair. The δ${\mathit{v}}_{\mathit{i}\mathit{j}}$(${\mathbf{P}}_{\mathit{i}\mathit{j}}$) are obtained from the v${\mathrm{̃}}_{\mathit{i}\mathit{j}}$ using relativistic mechanics. The ground states of ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ are calculated using the ${\mathit{H}}_{\mathit{R}}$ with the variational Monte Carlo method, and the results are compared with those obtained using the nonrelativistic ${\mathit{H}}_{\mathrm{NR}}$. Results of calculations including the three-nucleon interaction are also reported. The relativistic effects reduce the binding energies of ${}_{}{}^3{}_{}{}^{}\mathrm{H}$ and ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ by ∼0.34 and 2.02 MeV, and they do not change the momentum distribution of the nucleons in these nuclei significantly.

The derivation of the nucleon-nucleon force from the Skyrme model is reexamined. Starting from previous results for the potential energy of quasistatic solutions, we show that a calculation using the Born-Oppenheimer approximation, properly taking into account the mixing of nucleon resonances, leads to substantial central attraction. We obtain a potential that is in qualitative agreement with phenomenological potentials. We also study the nonadiabatic corrections, such as the velocity dependent transition potentials, and discuss their importance.

In view of the persisting misunderstandings about the determination of the pion-nucleon coupling constants in the Nijmegen multienergy partial-wave analyses of pp, np, and p¯p scattering data, we present additional information which may clarify several points of discussion. We comment on several recent papers addressing the issue of the pion-nucleon coupling constant and criticizing the Nijmegen analyses.

The electric monopole strength ${\mathrm{\rho }}^2$ for the $0_2^{+}$→$0_1^{+}$ transition and the B(E2) value for the $0_2^{+}$→$2_1^{+}$ transition were deduced from internal electron conversion and γ-ray spectroscopy and from the measurement of the lifetime of the $0_2^{+}$ state, performed by means of the Doppler shift attenuation method in gases. In addition, an upper limit was deduced for the E0 component of the $2_2^{+}$→$2_1^{+}$ transition. The available spectroscopic data on low-lying positive parity levels in ${}_{}{}^{78,80,82}{}_{}{}^{}\mathrm{Kr}$ are compared to the predictions of the interacting boson model (IBM-2).

We examine the status of the nuclear matter compressibility ${\mathit{K}}_{\mathrm{nm}}$ obtained from experimental data of the strength distribution of the giant monopole resonance in nuclei and employing a least-squares fit to a semiempirical expansion of the nucleus compressibility ${\mathit{K}}_{\mathit{A}}$ in ${\mathit{A}}^{\mathrm{-}1/3}$. We present arguments indicating that all the coefficients of this expansion must be determined by a fit to the data. In our analysis we have used the entire data set, correcting for systematic energy differences between data sets measured in different laboratories, and applying the same criteria to all sets in extracting the uncertainties. Contrary to recent statements by Sharma and collaborators, we find that the present complete data set is not adequate to limit the range of ${\mathit{K}}_{\mathrm{nm}}$ to better than about a factor of 1.7 (200 to 350 MeV).