Cross-section and vector-analyzing-power data for three star configurations of the ${}^2\mathrm{H}(p\to ,pp)n$ breakup reaction at $E_p^{\mathrm{lab}}=65\mathrm{}$ MeV were measured in a kinematically complete experiment. They are compared to rigorous Faddeev calculations involving five realistic charge-dependent nucleon-nucleon potentials: Argonne $v_{18},$ CD Bonn, Nijmegen 93, Nijmegen I, and Nijmegen II. A general satisfactory agreement between theory and experiment has been found. However, there exist also a few minor discrepancies in cross sections in some regions of phase space. The experimental data are compared also to the calculations including the (π-π) Tucson-Melbourne three-body force. Their effects are either negligible or increase the disagreement with the experiment.

We discuss the low-energy behavior of the spin-averaged amplitude of virtual Compton scattering off a nucleon. Based on gauge invariance, Lorentz invariance, and the discrete symmetries, it is shown that to first order in the frequency of the final real photon only two generalized polarizabilities appear. Different low-energy expansion schemes are discussed and put into perspective.

Strange matrix elements of the nucleon are calculated within the light-cone formulation of the meson cloud model. The $Q^2$ dependence of the strange vector and axial vector form factors is computed, and the strangeness radius and magnetic moment extracted, both of which are found to be very small and slightly negative. Within the same framework one finds a small but nonzero excess of the antistrange distribution over the strange at large $x$. Kaon loops are unlikely, however, to be the source of a large polarized strange quark distribution.

Using a quark model, we study the effect of charge symmetry breaking on the valence quark distributions of the nucleon. The effect due to quark mass differences and the Coulomb interaction of the electrically charged quarks is calculated and, in contrast to recent claims, found to be small. In addition, we investigate the effect of charge symmetry breaking in the confining interaction, and in the perturbative evolution equations used to relate the quark model distributions to experiment. We find that both these effects are small, and that the strong charge symmetry breaking effect included in the scalar confining interactions may be distinguishable from that generated by quark mass differences.

We calculate the electromagnetic moments and radii of the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ in the nonrelativistic quark model, including two-body exchange currents. We show that two-body exchange currents lead to nonvanishing $\Delta$ and $N\to \Delta$ transition quadrupole moments even if the wave functions have no $D$-state admixture. The usual explanation based on the single-quark transition model involves $D$-state admixtures but no exchange currents. We derive a parameter-free relation between the $N\to \Delta$ transition quadrupole moment and the neutron charge radius, namely $Q_{N\to \Delta }=(1/\sqrt{2}{)r}_n^2.$ Furthermore, we calculate the $M1\mathrm{}$ and $E2\mathrm{}$ amplitudes for the process $\gamma +N\to \Delta$. We find that the $E2\mathrm{}$ amplitude receives sizable contributions from exchange currents. These are more important than the ones that result from $D$-state admixtures due to tensor forces between quarks if a reasonable quark core radius of about 0.6 fm is used. We obtain a ratio of $E2/M1=-3.5\%$.

The recent ${\pi }^{+}p$ differential cross-section measurements between $20$ and $100$ MeV (pion lab kinetic energy) have been analyzed in the context of an extended threshold expansion of the $K$ matrix. The analysis shows that the bulk of the database is self-consistent. Our results in the $S_{31}$ channel disagree with the ones obtained in the Karlsruhe phase-shift analyses (which have been based exclusively on the old $\pi N$ database); we report differences of (approximately) one degree in the corresponding phase-shift values and of almost 25% in the $s$-wave scattering length $a_3$ (our value: $a_3=-0.077\pm 0.003$ $m_{\pi }^{-1})$. These differences reflect the extent of the discrepancy between the old and the new low-energy ${\pi }^{+}p$ database; they cannot be attributed to the method of the analysis. A comparison of the present result for the $a_3$ with the values of the $\pi N$ scattering lengths, recently obtained from measurements of the $1s$ energy-level shift and width in pionic hydrogen and deuterium, leads to the conclusion that, within the present (experimental and theoretical) accuracies, the various results are not incompatible with the isospin symmetry of the strong interaction.

No evidence for the neutrinoless double-$\beta$ decay of ${}^{100}$Mo has been found in a search using a segmented Si(Li) detector with source foils enriched to 97% ${}^{100}$Mo. From an exposure of 0.2664 mole years, and using Bayesian statistics to calculate confidence levels, we find a 68% lower limit on the half-life for the $J^p{=0\mathrm{}}^{+}\to 0^{+}$ transition of $0.22\times {10}^{23}$ yr. The measured half-life of the two neutrino double-$\beta$ decay is ${0.76}_{-0.14}^{+0.22\mathrm{}}\times {10}^{19}$ yr.

We show that the effects of neutrino oscillations on ${}^8$B solar neutrinos are described well by the first two moments (the average and the variance) of the energy distribution of scattered or recoil electrons. For the SuperKamiokande and the Sudbury Neutrino Observatory experiments, the differences between the moments calculated with oscillations and the standard, no-oscillation moments are greater than three standard deviations for a significant fraction of the neutrino mass-mixing $(\Delta m^2,{\sin }^{2}2\theta )$ parameter space.

Nuclear states in ${}^{56}$Ni, at an initial excitation energy $E^{*}=70\mathrm{}$ MeV, were populated via the isospin $T=0\mathrm{}$ reaction ${}^{16}$O${+}^{40}$Ca. The dilepton- ${(e}^{+}{e}^{-})$ pairs and photon-decay yields were measured simultaneously. Statistical decay calculations describe well both measurements on an absolute scale. The isospin mixing parameter extracted from these measurements $({\alpha }^2=0.065)$ is consistent with other studies of the isospin symmetry in highly excited compound nuclei. The $1\sigma$ upper limit for the observed monopole strength is 4.3 nb, which is 3 times higher than the one sum rule value calculated with the statistical model for the decay of the compound nucleus.

High-spin states have been populated in ${}^{171}$Hf with the ${}^{48}$Ca+${}^{128}$Te reaction at 200 MeV. A three-quasiparticle strongly coupled rotational band has been established in ${}^{171}$Hf which is built upon the known $K^{\pi }{=19/2\mathrm{}}^{+}$, 6.2 ns, isomeric state. In addition the strongly coupled band built upon the $K^{\pi }{=23/2\mathrm{}}^{-}$, 18 ns, isomeric state in ${}^{171}$Hf has been extended to higher excitation energy. ${(g}_K-g_R{)/Q}_0$ values, determined from the $(\Delta I=1)/(\Delta I=2)$ branching ratios, have been used in combination with the aligned angular momentum to confirm the configuration assignments for each band. Three new $\gamma$-ray transitions have also been established in ${}^{171}$Hf which link the $K^{\pi }{=19/2\mathrm{}}^{+}$, 6.2 ns, isomeric bandhead state directly into the yrast states. The reduced hindrance factors for these decays are discussed.

High spin states in the doubly odd ${}^{120}\mathrm{I}$ nucleus have been investigated through in-beam gamma-ray spectroscopy following the ${}^{108}{\mathrm{P}\mathrm{d}+}^{16}\mathrm{O}$ and ${}^{114}{\mathrm{C}\mathrm{d}+}^{11}\mathrm{B}$ fusion-evaporation reactions. A new ΔI=1 collective band, based on the π${\mathrm{g}}_{7/2}$⊗υ${\mathrm{h}}_{11/2}$ quasiparticle configuration, has been identified. This band exhibits energy staggering in the odd-even spin states and is found to be intense as compared to the earlier known π${\mathrm{g}}_{9/2}^{\mathrm{-}1}$⊗υ${\mathrm{h}}_{11/2}$ nonstaggered band. A loss in collectivity is observed at the ${\mathrm{I}}^{\mathrm{\pi }}$${=(23\mathrm{}}^{\mathrm{-}}$) state, implying an abrupt band termination.

Binary-reaction channels of ${}^{19}\mathrm{F}{+}^{12}\mathrm{C}$ have been studied at $E_{\mathrm{lab}}{(}^{19}\mathrm{F})=92\mathrm{}\hspace{0.5em}\mathrm{MeV}$ using kinematic coincidence techniques. The results are discussed in the light of previous inclusive measurements performed at the same incident energy and for which the occurrence of an important incomplete fusion mechanism after projectile breakup was proposed. Evidence for strong damped binary, especially quasisymmetric, decay processes is found.

An “identical” superdeformed (SD) band has been discovered in the nucleus ${}^{130}$Ce. This band has transition energies which are identical to the half-way points between the energies in the yrast SD band of ${}^{131}$Ce to a mean degeneracy of 0.4$\%$. The discovery of this band completes the chain of SD Ce isotopes from ${}^{129}$Ce to ${}^{133}$Ce. However, at $0.5\%$ of the reaction channel, it is populated with an intensity which is an order of magnitude smaller than neighboring SD bands. The valence neutron configuration is assigned as $\nu 6^1$ with a hole in either the $\left[523\right]{7/2}^{-}$ or $\left[411\right]{1/2}^{+}$ Nilsson orbitals.

It is known now that chiral symmetry restoration requires the meson-nucleon couplings to be density-dependent in nuclear-matter mean-field models. We further show that, quite generally, the quark and gluon condensates in medium are related to the trace of the energy-momentum tensor of nuclear matter and in these models the incompressibility $K$ must be less than 3 times the chemical potential $\mu$. In the critical density ${\rho }_c,$ the gluon condensate is only reduced by $20\%$, indicating a larger effective nucleon mass.

Rigorous calculations of proton-deuteron and neutron-deuteron analyzing power $A_y\left(\theta \right)$ angular distributions in the incident nucleon energy range from 1 to 3 MeV are presented. It is shown that the sizable difference in the magnitude of $A_y\left(\theta \right)$ for $p$-$d$ and $n$-$d$ scattering is caused by the Coulomb interaction in the case of $p$-$d$ scattering and is not due to charge-symmetry-breaking effects in the ${}^3{P}_J$ nucleon-nucleon interactions. The calculated relative difference in the angular region of the $A_y\left(\theta \right)$ maximum is in agreement with the existing experimental data.

Bond percolation model predictions for the behavior of scaled factorial moments (SFM’s) of cluster size distributions do not show intermittency for “near-critical” events. An intermittentlike signal is observed only for “overcritical” events, independent of the size of the lattice. SFM analysis of ALADIN experimental data (600, 800, and 1000 MeV/nucleon Au + Au reactions) is in qualitative agreement with the percolation predictions.

Meson exchange currents (MEC’s) can induce an enhancement of the $B\left(M1\mathrm{}\right)\mathrm{}$ strength in nuclei over the corresponding Gamow-Teller strength. Such an increase was observed in ${}^{28}$Si [C. Lüttge et al., Phys. Rev. C 53, 127 (1996)], but the experimental ratio was much larger than shell model predictions using the unified $\mathrm{sd}$-shell interaction and corrections to the $g$ factors which incorporate MEC effects. It is pointed out that, when taking the Gamow-Teller strength from a reanalysis of the ${}^{28}$Si$\mathrm{}(p,n)\mathrm{}$ data as well as from a recent ${}^{28}{\mathrm{S}\mathrm{i}(}^3\mathrm{H}\mathrm{e},t)$ experiment, the derived ratio is now in good agreement with the shell model results. This finding provides strong support that the observed enhancement is due to meson exchange currents.

The lack of $p$-wave strength in a recent measurement of the low-energy ${}^7$Li(n,${\gamma }_0{)}^8$Li cross section, as compared with significant strength found in the ${}^7$Li(p,${\gamma }_0{)}^8$Be reaction, may be attributed to the qualitatively different low-energy behaviors of penetration factors for neutron and charged-particle channels.

We study the low-energy ${3/2}^{-}$ and ${1/2}^{-}$ states of ${}^5$He and ${}^5$Li in a microscopic cluster model. The scattering phase shifts of Bond $(\alpha +n)$ and of Schwandt $(\alpha +p)$, respectively, are well reproduced. We determine the resonance parameters by localizing the poles of the analytically continued $S$ matrix at complex energies. Our results differ from conventional $R$-matrix resonance parameters, that were extracted from experimental data using the definition of a resonance based on the positions and widths of reaction cross section peaks. However, they nicely agree with the results of an extended $R$-matrix method that works at complex energies.

A new parametrization for an effective nonlinear Lagrangian density of relativistic mean field (RMF) theory is proposed, which is able to provide a very good description not only for the properties of stable nuclei but also for those far from the valley of beta stability. In addition the recently measured superdeformed minimum in the ${}^{194}$Hg nucleus is reproduced with high accuracy.