Parity violating electron nucleus scattering is a clean and powerful tool for measuring the spatial distributions of neutrons in nuclei with unprecedented accuracy. Parity violation arises from the interference of electromagnetic and weak neutral amplitudes, and the $Z^0$ of the standard model couples primarily to neutrons at low $Q^2.$ The data can be interpreted with as much confidence as electromagnetic scattering. After briefly reviewing the present theoretical and experimental knowledge of neutron densities, we discuss possible parity violation measurements, their theoretical interpretation, and applications. The experiments are feasible at existing facilities. We show that theoretical corrections are either small or well understood, which makes the interpretation clean. The quantitative relationship to atomic parity nonconservation observables is examined, and we show that the electron scattering asymmetries can be directly applied to atomic parity nonconservation because the observables have approximately the same dependence on nuclear shape.

We have solved the Faddeev equations for $\eta d$ elastic scattering using realistic separable interactions for the $\mathrm{NN}$ and coupled $\eta N$-$\pi N$ subsystems. We found that including explicitly the pion channel in the integral equations drastically reduces the attraction that is present in the system. As a consequence, the existence of a $\eta \mathrm{NN}$ quasibound state is excluded by the modern $\eta N$ amplitude analysis.

We analyze reactions of several types that are naively below threshold but can proceed because of the release of binding energy from nuclear fission and occasionally the formation of Coulombic bound states. These reactions include (i) photofission with pion production and (ii) charged current neutrino-nucleus reactions that lead to fission and/or formation of a Coulomb bound state of a ${\mu }^{-}$ with the nucleus of a fission fragment. We comment on the possible experimental observation of these reactions.

We show that the QCD van der Waals attractive potential is strong enough to bind a $\phi$ meson onto a nucleon inside a nucleus to form a bound state. The direct experimental signature for such an exotic state is proposed in the case of subthreshold $\phi$ meson photoproduction from nuclear targets. The production rate is estimated and such an experiment is found to be feasible at the Jefferson Laboratory.

The exactly solvable model with fermion boson coupling proposed by Schütte and Da Providencia is considered with spontaneously broken symmetry within the so-called self-consistent random phase approximation. Encouraging results for ground and excited states are obtained. A possible extension of the present approach is discussed.

Using an unusual technique for precisely locating γ ray peaks in a spectrum from a Ge semiconductor detector, the energy of the 2.31-MeV γ ray which follows ${}^{14}\mathrm{O}$ positron decay has been measured on a scale derived from the known energies of ${}^{56}\mathrm{Co}$ lines, as have the energies of the 2.18- and 2.32-MeV γ rays which follow the decay of ${}^{90}\mathrm{Nb}.$ Values of 2312.603(10), 2186.253(10), and 2318.973(10) keV, respectively, were determined. When taken together with updated, previously accepted values, these lead to recommended energies of 2312.590(10), 2186.244(7), and 2318.962(6) keV.

In this work, an improved quark model approach to the $\omega$ meson photoproduction with an effective Lagrangian is presented. The t-channel natural-parity exchange is taken into account through the Pomeron exchange, while the unnatural-parity exchange is described by the ${\pi }^0$ exchange. With a very limited number of parameters, the available experimental data in the low energy regime can be consistently accounted for. We find that the beam polarization observables show sensitivities to some s-channel individual resonances in the $\mathrm{SU}\mathrm{}\left(6\right)\mathrm{}\otimes \mathrm{O}\mathrm{}\left(3\right)\mathrm{}$ quark model symmetry limit. Especially, the two resonances $P_{13}\mathrm{}\left(1720\right)\mathrm{}$ and $F_{15}\mathrm{}\left(1680\right),$ which belong to the representation $[56{,}^{2}8,2,2,J],$ have dominant contributions over other excited states. Concerning the essential motivation of searching for “missing resonances” in meson photoproduction, this approach provides a feasible framework, on which systematic investigations can be done.

The ${}^5\mathrm{H}$ nucleus is investigated in the generator coordinate method, using ${}^3\mathrm{H}+n+n$ three-cluster wave functions. The model is tested with the ${}^3\mathrm{H}+n$ and ${}^3\mathrm{He}+p$ properties which agree fairly well with the experimental data. The ${}^5\mathrm{H}$ energy is found to be $E\approx 3\hspace{0.5em}\mathrm{MeV}$ with respect to the ${}^3\mathrm{H}+n+n$ threshold, and the neutron width is ${\Gamma }_n\approx 1–2\hspace{0.5em}\mathrm{MeV}$ or ${\Gamma }_n\approx 1–4\hspace{0.5em}\mathrm{MeV},$ according to the nucleon-nucleon interaction. We therefore suggest that the ${}^5\mathrm{H}$ lifetime should be larger than the ${}^4\mathrm{H}$ lifetime $({\Gamma }_n\approx 5–6\hspace{0.5em}\mathrm{MeV}).\mathrm{}$

Multifragmentation resulting from an expanding nuclear matter is investigated on the basis of quantum molecular dynamics. In particular, the dependence of the fragment mass distribution on the initial temperature ${(T}_{\mathrm{init}})$ and the radial flow velocity $\mathrm{}\left(h\right)\mathrm{}$ is studied. When $h$ is large, the distribution shows exponential shape, whereas for small $h,$ it obeys the power law. Although the power law is what Fisher’s droplet model predicts, the fragmentation mechanism in an expanding system is found to be different from the one in a thermally equilibrated system.

The role of the nucleon resonances ${(N}^{*})$ in $\omega$ photoproduction is investigated by using the resonance parameters predicted by Capstick and Roberts [Phys. Rev. D 46, 2864 (1992); 49, 4570 (1994)]. In contrast with the previous investigations based on the $\mathrm{SU}\mathrm{}\left(6\right)\mathrm{}\times \mathrm{O}\mathrm{}\left(3\right)\mathrm{}$ limit of the constituent quark model, the employed $N^{*}\to \gamma N$ and $N^{*}\to \omega N$ amplitudes include the configuration mixing effects due to the residual quark-quark interactions. The contributions from the nucleon resonances are found to be significant relative to the nonresonant amplitudes in changing the differential cross sections at large scattering angles and various spin observables. In particular, we suggest that a crucial test of our predictions can be made by measuring the parity asymmetry and beam-target double asymmetry at forward scattering angles. The dominant contributions are found to be from $N{\frac{3}{2}}^{+}\mathrm{}\left(1910\right),$ a missing resonance, and $N{\frac{3}{2}}^{-}\mathrm{}\left(1960\right)\mathrm{}$ which is identified as the $D_{13}\mathrm{}\left(2080\right)\mathrm{}$ of the Particle Data Group.

Inhomogeneous pseudoscalar and scalar Bethe-Salpeter equations solved using a renormalization-group-improved rainbow-ladder truncation exhibit bound state poles below and above $T_c,$ the critical temperature for chiral symmetry restoration. Above $T_c$ the bound state amplitudes are identical, as are the positions and residues of the pseudoscalar and scalar poles in the vertices. In the chiral limit the ${\pi }^0\to \gamma \gamma$ coupling vanishes at $T_c,$ as do $f_{\pi },$ $m_{\sigma },$ and $g_{\sigma \pi \pi }.$ For light current-quark masses the $2\pi$ decay channel of the isoscalar-scalar bound state remains open until very near $T_c,$ and the widths of the dominant pion decay modes remain significant in the vicinity of the crossover.

Angular distributions of the $\alpha$-particle production differential cross section from the breakup of ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ projectiles incident on a ${}^{208}\mathrm{Pb}$ target have been measured at seven projectile energies between 29 and 52 MeV. The $\alpha$-breakup cross section of ${}^6\mathrm{Li}$ was found to be systematically greater than that of ${}^7\mathrm{Li}$ across the entire energy range. These data have been compared with previously reported results and with the predictions of continuum-discretized coupled channels (CDCC) calculations including resonant and nonresonant projectile breakup. The present data compare well with previous measurements, while the CDCC calculations provide a reasonable prediction of the relative $\alpha$-breakup cross sections but underpredict their absolute values. The calculations confirm that a major factor in the enhancement of the ${}^6\mathrm{Li}$ to ${}^7\mathrm{Li}$ $\alpha$-breakup cross section is the difference between the $\alpha$-breakup thresholds of the two isotopes. These results have implications for structural studies of light exotic nuclei based on elastic scattering.

High precision g factors and $B\left(E2\mathrm{}\right)\mathrm{}$ values were obtained in measurements of the first $2^{+}$ states of ${}^{58-64}\mathrm{Ni}$ using the technique of projectile Coulomb excitation in combination with transient magnetic fields. The new results are well explained by large-scale shell model calculations in which, for ${}^{58-62}\mathrm{Ni},$ up to $t=5\mathrm{}$ nucleons are excited from the $f_{7/2}$ shell into the remaining $\mathrm{fp}$ shell orbits. A complete calculation was carried out for ${}^{64}\mathrm{Ni}.$ The g factor of ${}^{58}\mathrm{Ni}$ is particularly surprising as it is small but definitely positive, a result which was not expected and therefore not considered in several earlier calculations. This observation can be explained by strong coupling of valence particles to an excited ${}^{56}\mathrm{Ni}$ core in accordance with recent Monte Carlo shell model calculations.

The individual lifetimes of three low-lying states in the proton-decaying well-deformed rotational band in the second minimum of the $N=Z$ nucleus ${}^{58}\mathrm{Cu}$ were determined. Doppler-shift attenuated $\gamma$-ray lineshapes were analyzed following the fusion-evaporation reaction ${}^{40}\mathrm{Ca}{(}^{24}\mathrm{Mg},1\mathrm{}\alpha {1p1n)}^{58}\mathrm{Cu}$ and using the EUROBALL γ-ray spectrometer coupled to ancillary detector systems. The deduced transitional quadrupole moments confirm the predicted increase of deformation towards the bottom of the band. The γ decay-out strength hints towards a nonstatistical pattern.

Microcanonical calculations are no more difficult to implement than canonical calculations in the lattice gas model. We report calculations for a few observables where we compare microcanonical model results with canonical model results.

We show that the neutron and proton transition densities predicted by recent quantum Monte Carlo calculations for $A=6,7\mathrm{}$ nuclei are consistent with pion scattering from ${}^6\mathrm{Li}$ and ${}^7\mathrm{Li}$ at energies near the $\Delta$ resonance. This has provided a microscopic understanding of the enhancement factors for quadrupole excitations, which were needed to describe pion inelastic scattering within the nuclear shell model of Cohen and Kurath.

The Kerman-Klein formulation of the equations of motion for a nuclear shell model and its associated variational principle are reviewed briefly. It is then applied to the derivation of the self-consistent particle-rotor model and of the self-consistent cranking model, for both axially symmetric and triaxial nuclei. Two derivations of the particle-rotor model are given. One of these is of a form that lends itself to an expansion of the result in powers of the ratio of single-particle angular momentum to collective angular momentum, which is essential to reach the cranking limit. The derivation of the latter also requires a distinct, angular-momentum violating step. The structure of the result implies the possibility of tilted-axis cranking for the axial case and full three-dimensional cranking for the triaxial one. The final equations remain number conserving.

A limitation common to all extensions of random-phase approximation including only particle-hole configurations is that they violate to some extent the energy weighted sum rules. Considering one such extension, the improved RPA (IRPA), already used to study the electronic properties of metallic clusters, we show how it can be generalized in order to eliminate this drawback. This is achieved by enlarging the configuration space, including also elementary excitations corresponding to the annihilation of a particle (hole) and the creation of another particle (hole) on the correlated ground state. The approach is tested within a solvable 3-level model.

Results of shell-model calculations for lower $\mathrm{fp}$-shell nuclei show that SU(3) symmetry breaking in this region is driven by the single-particle spin-orbit splitting. However, even though states of the yrast band exhibit SU(3) symmetry breaking, the results also show that the yrast band $B\left(E2\mathrm{}\right)\mathrm{}$ values are insensitive to this fragmentation of the SU(3) symmetry; specifically, the quadrupole collectivity as measured by $B\left(E2\mathrm{}\right)\mathrm{}$ transition strengths between low lying members of the yrast band remain high even though SU(3) appears to be broken. Results for ${}^{44,46,48}\mathrm{Ti}$ and ${}^{48}\mathrm{Cr}$ using the Kuo-Brown-3 two-body interaction are given to illustrate these observations.