$N/Z$ dependence of core polarization charges for electric quadrupole transitions is studied in C isotopes by using a microscopic particle-vibration model in which Hartree-Fock and random-phase approximations are used to calculate the single-particle wave functions and giant quadrupole resonances. A large quenching of the polarization charges is found in nuclei with a large $N/Z$ ratio. Recent experimental data of quadrupole moments of ${}^{15}\mathrm{B}$ and ${}^{17}\mathrm{B}$ are reproduced well by using the calculated polarization charges for shell-model wave functions.

We calculate polarized quark distribution functions and $g_1$ structure functions for the nucleon. The calculation is performed in the light-cone frame. The dressed nucleon is assumed to be a superposition of the bare nucleon plus virtual light-cone Fock states of baryon-meson pairs. For bare nucleon we consider both the case of diquark-quark clusterization and the case which there is no quark clusterization inside the nucleon. The initial distributions are evolved. The final results are compared with other theoretical calculations and experimental observations.

The $\gamma$ decays of excited states in the neutron deficient nuclei ${}^{159}\mathrm{Ta}$ and ${}^{160}\mathrm{W}$ have been identified for the first time. The nuclei of interest were produced in reactions induced by beams of ${}^{58}\mathrm{Ni}$ ions at energies of 286 MeV, 291 MeV, and 298 MeV bombarding a ${}^{106}\mathrm{Cd}$ target. Prompt $\gamma$ rays were recorded using the JUROSPHERE spectrometer and were tagged through the subsequent $\alpha$ decays of associated recoil ions measured in a position-sensitive silicon strip detector at the focal plane of the gas-filled separator RITU. Level schemes have been deduced and compared with similar structures observed in neighboring nuclei.

Nuclei reached in r- and $\mathrm{rp}$-process reactions in nuclear astrophysics are considerably more neutron or proton rich than most nuclei for which level densities have been studied. Two models which predict somewhat different behavior for nuclei away from the valley of stability are examined. It is found that one of the two provides a better description of the available data. A term which lowered the level density parameter as isospin increased at fixed A did not produce as much improvement as one which reduced the level density parameter based on the distance from the valley of stability. As a by-product of this study, a formulation of level density systematics near the valley of stability is also tested.

A schematic model explaining the recent evidence for bound states of the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ resonance in ${}^{12}\mathrm{C}$ with a width of about 5 MeV found in the ${}^{12}\mathrm{C}{(e,e}^{\prime }p{\pi }^{-}{)}^{11}{\mathrm{C}}_{\mathrm{g}.\mathrm{s}.\mathrm{}}$ is suggested. It interprets the observed narrow resonances as coherent bound states enforcing a fixed phase relation for the rescattering of the decay $\pi$’s in the nucleus. The coherent summing of the rescattering diagrams results in a cancellation of the tails of the resonance and a constructive interference in the maximum of the resonance leading to the observed narrow states at the maximum of the $\Delta \mathrm{}\left(1232\right)\mathrm{}$ shifted by the binding energy. The same mechanism may contribute to narrow $\Sigma$ hypernuclear states and explains their successful and failed observation, respectively.

In this paper we present the systematics of nuclear deformation for even-even, even-odd, odd-even, and doubly odd nuclei in four regions: the $50<Z<~66$ and $82<N<~104$ region, the $66<Z<\mathrm{}82\mathrm{}$ and $82<N<~104$ region, the $66<Z<\mathrm{}82\mathrm{}$ and $104<N<\mathrm{}126\mathrm{}$ region, and the $82<Z<~104$ and $126<N<~155$ region. Compact trajectories are obtained using the ${P=N}_p{N}_n{/(N}_p{+N}_n)$ factor. It is found that there are no apparent shifts in the trajectories between the even-even nuclei previously studied with the P factor, and the other classes of nuclei included here. This may suggest that the pairing interaction strength of even-even nuclei is very close to that in their odd A and doubly odd neighbors. Strong anomalies around the $Z\sim 80$ region are highlighted.

Three odd-odd $N=73\mathrm{}$ isotones, namely ${}^{128}\mathrm{Cs},$ ${}^{130}\mathrm{La},$ and ${}^{132}\mathrm{Pr},$ have been studied via (HI, $\mathrm{xn}\gamma )$ reactions. In all three cases, $\Delta I=1\mathrm{}$ side bands of the $\pi h_{11/2}\nu h_{11/2}$ yrast bands were discovered. This extends the systematic observation of nearly degenerate $\pi h_{11/2}\nu h_{11/2}$ doublet bands in the neighboring $N=75\mathrm{}$ isotones; these were interpreted as resulting from chiral symmetry breaking in the intrinsic body-fixed frame.

We calculate the information entropy of single-particle states in position space $S_r$ and momentum space $S_k$ for a nucleon in a nucleus, a $\Lambda$ particle in a hypernucleus, and an electron in an atomic cluster. It is seen that $S_r$ and $S_k$ obey the same approximate functional form as functions of the number of particles $S_r\hspace{0.5em}(or\hspace{0.5em}{S}_k{)=a+bN}^{1/3}$ in all of the above many-body systems in position and momentum space separately. The net information content $S_r{+S}_k$ is a slowly varying function of N of the same form as above. The entropy sum $S_r{+S}_k$ is invariant to a uniform scaling of coordinates, and is a characteristic of the single-particle states of a specific system. The order of single-particle states according to $S_r{+S}_k$ is the same as their classification according to energy, keeping the quantum number n constant. The spin-orbit partners are ordered correctly. It is also seen that $S_r{+S}_k$ is enhanced by the excitation of a fermion in a quantum-mechanical system. Finally, we obtain a relationship of $S_r{+S}_k$ with the energy of the corresponding single-particle state, i.e., $S_r{+S}_k=k\ln (\mu E+\nu ).\mathrm{}$ This relation holds for all systems under consideration.

We study the properties of hypernuclei containing one $\Lambda$ hyperon in the framework of the correlated basis function theory with Jastrow correlations. Fermi hypernetted chain integral equations are derived and used to evaluate energies and one-body densities of $\Lambda$ hypernuclei having a doubly closed shell nucleonic core in the $\mathrm{jj}$ coupling scheme, from carbon to lead. We also study hypernuclei having the least bound neutron substituted by the $\Lambda$ particle. The semirealistic Afnan and Tang nucleon-nucleon potential and Bodmer and Usmani $\Lambda$-nucleon potential are adopted. The effect of many-body forces are considered by means either of a three-body $\Lambda$-nucleon-nucleon potential of the Argonne type or of a density-dependent modification of the $\Lambda$-nucleon interaction, fitted to reproduce the $\Lambda$ binding energy in nuclear matter. While Jastrow correlations underestimate the attractive contribution of the three-body $\Lambda$ interaction, the density-dependent potential provides a good description of the $\Lambda$ binding energies over all the nuclear masses range, in spite of the relative simplicity of the model.

The reactions ${}^3\mathrm{H}{(}^3\mathrm{H}{,2n)}^4\mathrm{He}$ and ${}^3\mathrm{He}{(}^3\mathrm{He}{,2p)}^4\mathrm{He}$ are investigated within a fully microscopic cluster model featuring a three-cluster exit channel. A hyperspherical harmonics basis is used to describe the three-cluster continuum. The resulting astrophysical S factor of both reactions is in good agreement with experimental data. Analysis of the low-energy scattering parameters reveals no evidence for a hidden resonance state that would increase the cross section of the reactions, and would help to resolve the solar neutrino problem.

We critically discuss a recent suggestion to use long-range modes of charge (electric or baryon) fluctuations as a signal for the presence of quark-gluon plasma at the early stages of a heavy ion collision. We evaluate the rate of diffusion in rapidity for different secondaries, and argue that for conditions of the Super Proton Synchrotron (SPS) experiments, it is strong enough to relax the magnitude of those fluctuations almost to its equilibrium values, given by hadronic “resonance gas.” We evaluate the detector acceptance needed to measure such “primordial” long-range fluctuations at Relativistic Heavy Ion Collider (RHIC) conditions. We conclude with an application of the charge fluctuation analysis to the search for the QCD critical point.

We calculate the cross sections for reactions of the $J/\psi$ with light mesons. We also evaluate its finite temperature spectral function. We investigate separately the role of elastic and inelastic channels and we compare their respective importance. We describe $J/\psi$ absorption channels that have not been considered previously to our knowledge. The relevance of our study to heavy ion collisions is discussed.

The giant resonance region from $10<\mathrm{}{E}_x<55\mathrm{}\mathrm{MeV}$ in ${}^{40}\mathrm{Ca}$ has been studied with inelastic scattering of 240-MeV α particles at small angles including 0°. Strength corresponding to $97\pm 11\%,$ $108\pm 12\%,$ and $62+10–20\%$ of the isoscalar $E0,$ $E2,$ and $E1\mathrm{}$ sum rules, respectively, was identified with centroids of $19.18\pm 0.37\mathrm{MeV},$ $17.84\pm 0.43\mathrm{MeV},$ $23.36\pm 0.70\mathrm{MeV},$ and rms widths of $4.88\pm 0.57\mathrm{MeV},$ $2.89\pm 0.60\mathrm{MeV},$ and $5.34\pm 0.90\mathrm{MeV}.$

A new approach to large-scale nuclear structure calculations, based on the density matrix renormalization group (DMRG), is described. The method is tested in the context of a problem involving many identical nucleons constrained to move in a single large-$j$ shell and interacting via a pairing plus quadrupole interaction. In cases in which exact diagonalization of the Hamiltonian is possible, the method is able to reproduce the exact results for the ground-state energy and the energies of low-lying excited states with extreme precision. Results are also presented for a model problem in which exact solution is not feasible.

In a kinematically complete experiment we have measured the two analyzing powers and the five spin correlation coefficients of the reaction $\overrightarrow{p}\overrightarrow{p}\to \mathrm{pp}{\pi }^0$ as a function of all five parameters of the three-body final state for bombarding energies between 325 and 400 MeV. The data are in disagreement with the theoretical predictions available at this time. Below 400 MeV, fewer than a dozen complex partial-wave amplitudes are likely to be significant, and it is expected that the present experimental information constrains these amplitudes. We also describe the formalism for an expansion of the spin observables into a complete set of angular functions and use this to completely characterize the polarization information obtainable from reactions with polarized spin-1/2 collision partners and a three-body final state.

Properties of microscopic interaction potentials between two ${}^{12}\mathrm{C}$ nuclei are discussed in connection with the formation of ${}^{12}{\mathrm{C}+}^{12}\mathrm{C}$ and $3\alpha +3\mathrm{}\alpha$ molecular resonances. The nucleus-nucleus interactions are calculated by the double-folding procedure based on a realistic nucleon-nucleon interaction (DDM3Y) and microscopic ${}^{12}\mathrm{C}$ transition densities calculated from 3α-RGM wave functions. The interaction potential can be written as the sum of the monopole part obtained from the monopole density and the multiple parts generated from the quadrupole component of the density. We discuss the role of the monopole and multipole parts of the potential separately. It is shown that the multipole part is very strong in the channels with $3\alpha +3\mathrm{}\alpha$ structure and the energy positions of the $3\alpha +3\mathrm{}\alpha$ molecular bands generated by the monopole potential are largely modified. The effect is moderate but non-negligible on the molecular bands with the ${}^{12}{\mathrm{C}+}^{12}\mathrm{C}$ dinuclearlike structure and largely modifies the band crossing diagram between the elastic and aligned-inelastic molecular bands. The channel coupling effect among the ${}^{12}{\mathrm{C}+}^{12}\mathrm{C}$ channels, namely, the elastic channel and the single- and mutual-$2_1^{+}$ excitation channels is also investigated. Due to the strong coupling between the ground and $2_1^{+}$ states of ${}^{12}\mathrm{C},$ the resonance wave functions obtained by the coupled-channel calculation have an additional radial node compared with those of the single-channel resonances. All the results are discussed in connection with the band crossing model which was believed to be successful in describing the ${}^{12}{\mathrm{C}+}^{12}\mathrm{C}$ molecular resonances.

A computation of the neutrinoless double-β-decay matrix elements is performed with the second quasirandom phase approximation method [A. A. Raduta, A. Faessler, S. Stoica, and W. A. Kaminski, Phys. Lett. B 254, 7 (1991); A. A. Raduta, A. Faessler, and S. Stoica, Nucl. Phys. A534, 149 (1991); S. Stoica and W. A. Kaminski, Phys. Rev. C 47, 867 (1993); S. Stoica, ibid. 49, 787 (1994); Phys. Lett. B 350, 152 (1995); S. Stoica and I. Mihut, Nucl. Phys. A602, 197 (1996)] for the nuclei with $A=76,$ 82, 96, 100, 116, 128, 130, and 136. It was found that the Ikeda sum rule is fulfilled with good accuracy and the results display a weak dependence on the single particle basis used. Comparing our calculations with similar ones performed with other quasirandom phase approximation–based methods we estimate more precisely the accuracy of these methods in the prediction of the neutrinoless matrix elements and neutrino mass parameter, which is settled to about 50% from their calculated values. Taking the most recent experimental limits for the neutrinoless half-lives, we also deduced new limits for the neutrino mass parameter.

The giant monopole, dipole, and quadrupole responses in ${}^{40}\mathrm{Ca},$ ${}^{90}\mathrm{Zr},$ ${}^{120}\mathrm{Sn},$ and ${}^{208}\mathrm{Pb}$ are investigated using linear response treatment based on a stochastic one-body transport theory. Effects of the coupling to low-lying surface modes (coherent mechanism) and the incoherent mechanism due to nucleon-nucleon collisions are included beyond the usual mean-field description. We emphasize the importance of both mechanisms in the fragmentation and damping of giant resonance. Calculated spectra are compared with experiment in terms of percentage of energy-weighted sum rules in various energy regions. We obtain reasonable agreement in all cases. Special attention has been given to the fragmentation of the giant quadrupole resonance in calcium and lead. In particular, the equal splitting of the $2^{+}$ in ${}^{40}\mathrm{Ca}$ is correctly reproduced. In addition, the appearance of fine structure in the response ${}^{208}\mathrm{Pb}$ is partly described by the calculations in which the coherent mechanism plays an important role.

$g$ factors have been measured for the first $2^{+}$ states of ${}^{58,60,62,64}\mathrm{Ni}$ isotopes employing the combined technique of projectile Coulomb excitation and transient magnetic fields. Lifetimes of low-lying states were redetermined using the Doppler shift attenuation method technique. The same target has been used in all measurements and the isotopes were provided by the ion source of the accelerator. These conditions guarantee high reliability and precision as demonstrated in earlier experiments. The measured g factors and the deduced $B\left(E2\mathrm{}\right)\mathrm{}$ values are well explained by large scale shell model calculations in which valence particles are strongly coupled to an excited ${}^{56}\mathrm{Ni}$ core.

The fission dynamics of excited nuclei is studied in the framework of the Langevin equation. One-body wall-and-window friction is used as the dissipative force in the Langevin equation. In addition to the usual wall formula friction, the chaos-weighted wall formula developed earlier is also considered here. The fission rate calculated with the chaos-weighted wall formula is found to be larger by about a factor of 2 compared to that obtained with the usual wall friction. The systematic dependence of the calculated fission width on temperature and spin of the fissioning nucleus is investigated and a simple parametric form of the fission width is obtained.