The yrast spectra with ${\mathit{J}}_{\max }^{\mathrm{\pi }}$=${10}^{+}$, B(E2) transition probabilities, and ${\mathit{Q}}_{\mathit{J}}^{+}$ values are calculated for even-even palladium isotopes by carrying out variation-after-projection calculations in conjunction with the Hartree-Fock-Bogoliubov (HFB) ansatz employing a pairing-plus-quadrupole-quadrupole effective interaction operating in a reasonably large valence space outside the ${}_{}{}^{76}{}_{}{}^{}\mathrm{Sr}$ core. Our calculations describe the shape changes as a function of mass number for palladium isotopes and also reveal that both the HFB technique and the quadrupole-quadrupole-plus-pairing model of the two-body interaction are fairly reliable in this mass region. © 1996 The American Physical Society.

We apply the equivalent photon approximation to calculate cross sections for the simultaneous excitation of two heavy ions in relativistic collisions. We study especially the excitation of two nuclei to a $1^{\mathrm{-}}$ state and show that the equations are symmetric with respect to both ions. We also examine the limit in which the excitation energy of one of the nuclei goes to zero, which gives the elastic case. Finally a few remarks about the limits of this approach are made. © 1996 The American Physical Society.

The influence of the nuclear Coulomb field on two-pion and two-kaon correlations is investigated for sources with charge number Z=160. The source radii extracted from the correlation function determined in sideward and outward directions are remarkably affected for meson pairs with average momenta below 200 MeV/c. © 1996 The American Physical Society.

Two recent papers give the energy of the first excited state of ${}_{}{}^9{}_{}{}^{}\mathrm{B}$ with uncertainties of ±0.1 and ±0.032 MeV. It is suggested that such high precision is not justified in either paper. © 1996 The American Physical Society.

The incompressibility of nuclear matter K, the Coulomb coefficient ${\mathit{K}}_{\mathit{c}}$, and the volume-symmetry coefficient ${\mathit{K}}_{\mathrm{vs}}$ of the nucleus incompressibility are studied using the relativistic mean field theory. It is found that K=300±50 MeV is necessary to account for the empirical values of K, ${\mathit{K}}_{\mathit{c}}$, and ${\mathit{K}}_{\mathrm{vs}}$, simultaneously, if the scaling model is valid. The result is independent of the details of the σ-meson self-interaction and is almost independent of the strength of the ω-meson self-interaction. However, a wider range of K may be available, if deviations from the scaling model are important. © 1996 The American Physical Society.

We use the experimental limit on the interference of M1 and E2 multipoles in the γ decay of ${}_{}{}^{57}{}_{}{}^{}\mathrm{Fe}$ to bound the time-reversal-violating parity-conserving ρNN vertex. Our approach is a large-basis shell-model calculation of the interference. We find an upper limit on the parameter g${\mathrm{¯}}_{\mathrm{\rho }}$, the relative strength of the T-violating ρNN vertex, of close to ${10}^{\mathrm{-}2}$, a value similar to the best limits from other experiments. © 1996 The American Physical Society.

It is shown that there exists a basis and a Hamiltonian within interacting boson model including g bosons that reproduce for even-even nuclei the geometric model results of Macchiavelli et al. [Phys. Rev. C 51, R1 (1995)] for ΔL=4 staggering. © 1996 The American Physical Society.

The electromagnetic form factor for the ${\mathit{K}}^0$ is calculated in a covariant formulation of the Salpeter equation for qq¯ bound states, which has been presented recently for the mass spectrum, decay properties, and form factors of the light pseudoscalar and vector mesons. The ${\mathit{K}}^0$ charge radius dependence on the difference between strange and down constituent quark mass is discussed. © 1996 The American Physical Society.

In this paper we discuss the most recent results concerning the Vlasov dynamics inside the spinodal region. The chaotic behavior which follows an initial regular evolution is characterized through the calculation of the fractal dimension of the distribution of the final modes excited. The ambiguous role of the largest Lyapunov exponent for unstable systems is also critically reviewed. This investigation seems to confirm the crucial role played by deterministic chaos in nuclear multifragmentation. © 1996 The American Physical Society.

Data of the (${\pi }^{+}, {\pi }^{-}$) reaction on ${}_{}{}^{128}{}_{}{}^{}\mathrm{Te}$ and ${}_{}{}^{130}{}_{}{}^{}\mathrm{Te}$ at $T_{\pi }=48\mathrm{}$ MeV are presented, which constitute also the first observation of pionic double charge exchange (DCX) on heavy nuclei at energies below the (3,3) resonance. For the ground state transitions in these isotopes we find very small cross sections of about 15 nb/sr only at 30° and a ratio of $\frac{\sigma \left({}_{}{}^{130}{}_{}{}^{}\mathrm{Te}\right)}{\sigma \left({}_{}{}^{128}{}_{}{}^{}\mathrm{Te}\right)}={1.5}_{-0.8\mathrm{}}^{+1.8\mathrm{}}$. The experimental results and their impact on the understanding of the $\beta \beta$ decay of the Te isotopes are discussed within the framework of recent proton-neutron quasiparticle random phase approximation calculations. For the transitions to the double isobaric analog states in ${}_{}{}^{128}{}_{}{}^{}\mathrm{Xe}$ and ${}_{}{}^{130}{}_{}{}^{}\mathrm{Xe}$ we obtain cross sections in the range 1 μb/sr which fit very well into a systematics, that is in accordance with a dominance of the short-range part of the DCX operator in analog transitions at low pion energies.

We study baryon spectroscopy including the effects of pseudoscalar meson exchange and one gluon exchange potentials between quarks, using nonperturbative, hyperspherical method calculations. We find that a model that includes only gluon exchange cannot simultaneously describe the Roper and $P$-wave excitation energies. Using only pseudoscalar meson exchange partially cures this problem, but at the cost of using a relatively large pion quark coupling constant. However, one gets a similar agreement with data in a model with both effects by using a quark-meson coupling constant compatible with the measured pion-nucleon coupling constant, and a value of ${\alpha }_s\approx 0.35$.

The position and movement of poles of the amplitude for elastic $\eta$-meson scattering off the light nuclei 2H, 3H, 3He, and 4He are studied. It is found that, within the existing uncertainties for the elementary $\eta N$ interaction, all these nuclei can support a quasibound state. The values of the $\eta$-nucleus scattering lengths corresponding to the critical $\eta N$ interaction that produces a quasibound state are given.

The contribution of nucleons to the quark condensate in nuclear matter includes a piece of first order in $m_{\pi }$, arising from the contribution of low-momentum virtual pions to the $\pi N$ $\sigma$ commutator. Chiral symmetry requires that no term of this order appears in the $\mathrm{NN}$ interaction. The mass of a nucleon in matter thus cannot depend in any simple way on the quark condensate alone. More generally, pieces of the quark condensate that arise from low-momentum pions should not be associated with partial restoration of chiral symmetry.

We measured cross sections and vector analyzing powers of the breakup reaction ${}_{}{}^2{}_{}{}^{}\mathrm{H}$(p→,pp)n at a laboratory proton energy of 19.0 MeV in four kinematically complete arrangements comprising space star, collinearity, final-state interaction, and quasifree scattering conditions. We present our results and compare them to the predictions of rigorous three-nucleon Faddeev calculations using different realistic nucleon-nucleon potentials. We found cases of good agreement but also cases of clear discrepancies. The inclusion of the 2π-exchange Tucson-Melbourne three-nucleon force does not remove these discrepancies but even worsens the description in all cases. In the quasifree scattering and space star configurations Coulomb-force effects might possibly be responsible for at least part of the observed discrepancies. © 1996 The American Physical Society.

The symmetry of diprotons leads to dramatic features in the ${}_{}{}^2{}_{}{}^{}\mathrm{He}$(γ→,pp) beam polarization asymmetry that are very different from those of deuteron photodisintegration. Calculations using realistic Faddeev wave functions show that striking features should persist for ${}_{}{}^1{}_{}{}^{}$${\mathit{S}}_0$ p-p pairs imbedded in ${}_{}{}^3{}_{}{}^{}\mathrm{He}$, and these challenge the simple interpretation given to recent ${}_{}{}^3{}_{}{}^{}\mathrm{He}$(γ,pp)n measurements. © 1996 The American Physical Society.

The meson-nucleon dynamics that generates the hard core of the RuhrPot two-nucleon interaction is shown to vanish in the irreducible 3N force. This result indicates a small 3N force dominated by conventional light meson-exchange dynamics and holds for an arbitrary meson-theoretic Lagrangian. The resulting RuhrPot 3N force is defined in the Appendix. A completely different result is expected when the Tamm-Dancoff–Bloch-Horowitz procedure is used to define the NN and 3N potentials. In that approach (e.g., full Bonn potential), both the NN and 3N potentials contain nonvanishing contributions from the coherent sum of meson-recoil dynamics and the possibility of a large hard core requiring explicit calculation cannot be ruled out. © 1996 The American Physical Society.

The usual theoretical treatments of the near-threshold pp→pp${\mathrm{\pi }}^0$ reaction are based on various phenomenological Lagrangians. In this work we examine the relationship between these approaches and a systematic chiral perturbation method. Our chiral perturbation calculation indicates that the pion rescattering term should be significantly enhanced as compared with the traditional phenomenological treatment, and that this term should have substantial energy and momentum dependence. An important consequence of this energy-momentum dependence is that, for a representative threshold kinematics and within the framework of our semiquantitative calculation, the rescattering term interferes destructively with the Born term in sharp contrast to the constructive interference obtained in the conventional treatment. This destructive interference makes theoretical cross sections for pp→pp${\mathrm{\pi }}^0$ much smaller than the experimental values, a feature that suggests the importance of the heavy-meson exchange contributions to explain the experimental data. © 1996 The American Physical Society.

The concept of factorial moments was applied to an analysis of the dynamical fluctuations in the charge distributions of the fragments emitted from gold nuclei with energies 10.6 and <1.0 GeV/nucleon interacting with emulsion nuclei. Clear evidence for intermittent fluctuations has been found in an analysis using all the particles released from the gold projectile, with a stronger effect observed below 1 GeV/nucleon than at 10.6 GeV/nucleon. For the full data sets, however, the intermittency effect was found to be very sensitive to the singly charged particles, and neglecting these particles strongly reduces the intermittency signal. When the analysis is restricted to the multiply charged fragments, an intermittency effect is revealed only for multifragmentation events, although one that is enhanced as compared to the analysis of all, singly and multiply charged, particles. The properties of the anomalous fractal dimensions suggest a sequential decay mechanism, rather than the existence of possible critical behavior in the process of nuclear fragmentation. The likely influence of the charge conservation effects and the finite size of decaying systems on the observed intermittency signals was pointed out. © 1996 The American Physical Society.