We develop a formalism for describing the 2ν mode of double-beta decay to an excited final state in the quasiparticle random phase approximation (QRPA). With this, we deduce the half-lives for the ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$ double-beta decays to both the ground and 1130 keV excited $0^{+}$ states in ${}_{}{}^{100}{}_{}{}^{}\mathrm{Ru}$. We predict the matrix elements of these two transitions to be of a similar magnitude. We also calculate the strengths of the associated single-beta decays from the ground state of the intermediate nucleus, ${}_{}{}^{100}{}_{}{}^{}\mathrm{Tc}$, and compare them with experiment. We find that the QRPA cannot simultaneously reproduce all of the experimental quantities, and, in particular, the single-beta transition between the initial and intermediate nuclei is overestimated by the theory. In addition, we demonstrate that the influence of the particle-particle force is an important factor in the calculation of both ${\mathrm{\beta }}^{\mathrm{-}}$ and ${\mathrm{\beta }}^{+}$ transition strengths.

In the framework of the Walecka model we show that a nucleon-meson form factor can improve the behavior of two-loop corrections for nuclear matter significantly. The effects of the vacuum fluctuations are strongly suppressed with respect to a calculation without form factors. The main contributions to the energy density are now given by nucleons in the Fermi sea.

The energy levels of the even-even Ge isotopes with mass number between 64 and 78 are studied in the model of the traditional interacting boson approximation. To account for the multiple band structure of these isotopes, one boson is allowed to break and form a fermion pair. The two fermions are allowed to excite to ${\mathit{f}}_{5/2}$ and ${\mathit{g}}_{9/2}$ single-particle orbitals. It was found that the energy levels of the ${}_{}{}^{64–78}{}_{}{}^{}\mathrm{Ge}$ isotopes can be reproduced reasonably.

The role of short range correlations on the depletion of the Fermi sea is studied in light nuclei. The short range correlations are considered in an approximate treatment allowing a systematic study of nuclei in the region 4≤A≤40. The ‘‘natural orbital’’ representation is used for the determination of the occupation probabilities of the shell model orbits of the ground-state wave function. The depletion of the nuclear Fermi sea appears to be, on the average, about 32%.

Isoscalar transition probabilities [B(ISλ)] have been obtained from the analysis of inelastic α scattering using double-folded optical α-nucleus potentials. The reliability of the proposed method was tested by applying it to three nuclei representing limiting cases of nuclear structure models. Data on ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}$ have been analyzed at ${\mathit{E}}_{\mathrm{\alpha }}$=23.5, 79.1, 104, and 139 MeV using the hydrodynamical model. For ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$ (${\mathit{E}}_{\mathrm{\alpha }}$=36 MeV) the model of the asymmetric rotor and for ${}_{}{}^{108}{}_{}{}^{}\mathrm{Pd}$ (${\mathit{E}}_{\mathrm{\alpha }}$=30.5 MeV) the model of the harmonic vibrator was considered. Excellent agreement of the extracted B(ISλ) values with the corresponding B(Eλ) values (obtained from electromagnetic probes) has been reached. The result of a lifetime measurement for the two-quadrupole-phonon $4^{+}$ state at 2055 keV in ${}_{}{}^{168}{}_{}{}^{}\mathrm{Er}$ has been confirmed.

Methods of boson mapping are tested in calculations for a simple model system of four protons and four neutrons in single-j distinguishable orbits. Two-body terms in the boson images of the fermion operators are considered. Effects of the seniority v=4 states are thus included. The treatment of unphysical states and the influence of boson space truncation are particularly studied. Both the Dyson boson mapping and the seniority boson mapping as dictated by the similarity transformed Dyson mapping do not seem to be simply amenable to truncation. This situation improves when the one-body form of the seniority image of the quadrupole operator is employed. Truncation of the boson space is addressed by using the effective operator theory with a notable improvement of results.

We present an extension of the semiclassical Thomas-Fermi model to relativistic systems. These are obtained by application of the gradient expansion scheme on the Wigner transformed Dyson equation. Explicitly we give the expansion of the Green’s functions, phase-space densities, and densities for a system of nucleons in a vector and scalar potential to second order.

The Lipkin model is used to study the transition to a parity-breaking system with the aim of understanding the features of negative parity low-lying levels associated with the octupole degree of freedom. The results of parity projection calculations for the energy splitting between the positive parity ground state and the lowest-lying negative parity state as well as the negative parity transition probability connecting them have been studied and compared to the exact results. A good agreement is observed for not-deformed and for well-deformed systems but at intermediate deformations the parity-projected results strongly differ from the exact ones. By anaylzing the parity-projected energy curves, two characteristic configurations are observed in the problem: the mean-field and the tunneling configurations. By mixing these two configurations, a substantial improvement over the parity projection method is obtained for the two quantities studied in all the regions of deformation. It is suggested that this method could be used in realistic calculations to improve the understanding of the octupole dynamics in opposition to the most powerful but expensive generator coordinate method.

Fusion cross sections have been measured for ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$${+}^{144}$Sm at bombarding energies in the range 46.5≤${\mathit{E}}_{\mathrm{lab}}$≤75 MeV by off-line observations of x rays and gamma rays emitted in the decay of the evaporation residues and their daughters. Elastic scattering angular distributions for the same system have also been measured in the range 49≤${\mathit{E}}_{\mathrm{lab}}$≤63 MeV. These data were used to obtain the parameters of an optical-model potential. It was found that a simultaneous description of both elastic scattering and fusion leads to an energy-dependent potential, with its real and imaginary parts connected by a dispersion relation.

Isomeric yield ratios for the reactions ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$(α,3n${)}^{108}$In, ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$(α,α3n${)}^{104}$Ag, ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$(α,2n${)}^{111}$In, and ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$(α,3n${)}^{110}$In are determined in the energy range of 20–63 MeV α particles. Excitation functions for the above reactions as well as for the ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$(α,2n${)}^{109}$In, ${}_{}{}^{107}{}_{}{}^{}\mathrm{Ag}$(α,α2n${)}^{105}$Ag, ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$(α,4n${)}^{109}$In, ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$(α,5n${)}^{108}$In, and ${}_{}{}^{109}{}_{}{}^{}\mathrm{Ag}$(α,α4n${)}^{105}$Ag reactions are also presented. Experimental excitation functions are compared with statistical model calculations taking into account precompound particle emission. Isomeric yield ratios are found to depend strongly on the root mean square orbital angular momentum in the entrance channel. A semiempirical method for the prediction of isomeric yield ratios failed to reproduce experimental data even for compoundlike reactions. Isomeric yield ratios were also calculated in the frame of a statistical model under consideration of angular momentum effects in the preequilibrium and the equilibrium stage. Overall agreement between the theory and the experiment for isomeric yield ratios was found to be satisfactory especially at low bombarding energy when compound nucleus reaction channel is dominant. The discrepancy observed at higher bombarding energies needs to be theoretically investigated in greater detail.

Inclusive neutron spectra were measured at 0°, 15°, 30°, 50°, 70°, 90°, 120°, and 160° from Ne-Pb collisions at 790 MeV/nucleon. A peak that originates from neutron evaporation from the projectile appears in the spectra at 0°. The shapes and magnitudes of the spectra are compared with those calculated from models of nucleus-nucleus collisions. The Boltzmann-Uehling-Uhlenbeck (BUU), intranuclear cascade (INC), and firestreak models agree generally with the measured double-differential cross sections and particularly at 50° and beyond; however, none of the models can reproduce the peaks at small angles (θ≤15°). The quantum molecular dynamics (QMD) model underestimates the spectra of the double-differential cross sections at all angles and energies for this asymmetric system. Also, the predictions of the INC model agrees with the angular distribution of the differential cross sections except that it underestimates the cross section at 0°; the BUU prediction overestimates the differential cross section at 0° and 90°; firestreak overpredicts at 15° and 30° and underpredicts at 70° and 90°; and the QMD model underpredicts the measured angular distribution and the energy spectra at forward angles.

Mass, velocity, and angular distributions have been measured for heavy products and for light charged particles from the reaction 215 MeV ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{27}$Al. Coincidences between evaporation residues and light charged particles have also been measured. Statistical-model calculations, incorporating light-particle decay from either the compound nucleus or the composite nucleus formed in the direct emission of a beam velocity particle, cannot account for the observed cross sections or angular distributions of the heavy residues. More elaborate kinematic simulations, which include direct light-particle emission as observed in the light-particle inclusive data, also do not work. This supports the notion that heavy fragment production (A>4) would be needed to account for the residue distributions.

Cross sections have been measured for proton emission following ${\mathrm{\pi }}^{+}$ absorption on ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$, for pion kinetic energies of 50, 100, 140, and 180 MeV using a large-solid-angle bismuth germanate detector array.

We derive and calculate the multiple scattering expansion of the Kerman-McManus-Thaler optical potential to second order in the free nucleon-nucleon transition amplitude and clarify the physical content of the interaction. Calculations are presented for the elastic scattering of protons from ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ at 135, 200, and 300 MeV incident energies, paying particular attention to the nonlocalities inherent in the second-order potential. It is shown that these effects result in a significant reduction in the proton-target absorption.

A nonlocal optical model is used to analyze the scattering of neutrons by ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$, ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$, ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$, and ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$ in the energy region from about 13 to 40 MeV. The real part of the internuclear interaction is obtained by using the prescription of a recently proposed nucleon + nucleus model K, which is a microscopic model based on the resonating-group formulation. A simple approximation, called the spherical approximation, is introduced to treat the cases involving non-closed-subshell target nuclei. The imaginary part used is purely phenomenological, and is obtained by simply adopting the imaginary potentials which have been found previously by other authors in their analyses with the usual local optical model. The influence of the Perey effect is taken into account by the introduction of an additional multiplicative factor. The results obtained for the differential scattering cross sections and the analyzing powers are quite satisfactory. The essential characteristics of the measured angular distributions are well reproduced. This suggests that model K is a viable model of great simplicity and can be employed to make systematic and large-scale analyses of all existing nucleon + nucleus scattering data.

We investigate the dynamics of nuclear fission, assuming purely diffusive motion up to the saddle point. The resulting Smoluchowski equation is solved for conditions appropriate to the ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$${+}^{142}$Nd${\to }^{158}$Er reaction at 207 MeV. The solution is characterized by an equilibration time ${\mathrm{\tau }}_0$ for the system to reach steady state, and the fission decay rate in steady state, Λ. We find that the equilibration time ${\mathrm{\tau }}_0$ plays a very small role in determining the number of prescission neutrons. The diffusion coefficient extracted from the experimental data is larger than the theoretical in the work of Bush, Bertsch, and Brown by a factor of 5–11.

Collisions of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$+Al, Cu, and Pb at ${\mathit{E}}_{\mathrm{lab}}$=14.6 GeV/nucleon were studied at the Brookhaven National Laboratory Alternating Gradient Synchrotron. Charged particle multiplicity was measured over the pseudorapidity interval 0.875≤η≤3.86 with a silicon pad detector. A strong correlation is seen between the multiplicity and the transverse energy measured in the interval -0.5≤η≤0.8. Correlation with the energy going forward after the collision and comparison with calculations indicate that rescattering is required to explain the data. The data are compared under the assumption of Koba-Nielson-Olesen scaling. The measured multiplicity scales approximately with the total number of participant nucleons and less well with the available center-of-mass kinetic energy.

Relativistic heavy ion collisions constitute a prolific source of hyperons: tens of hyperons per event are predicted at energies E≥10 GeV/nucleon, providing a scenario for the formation of metastable exotic multihypernuclear objects. They may exhibit exceptional properties: bound neutral (e.g., ${}_{}{}^4{}_{}{}^{}$${\mathit{M}}_{2\mathrm{\Lambda }}^{2\mathit{n}}$, ${}_{}{}^{10}{}_{}{}^{}$${\mathit{M}}_{2\mathrm{\Lambda }}^{8\mathit{n}}$, pure Λ droplets, ${}_{}{}^8{}_{}{}^{}\mathrm{\Lambda }$) and even negatively charged composites objects with positive baryon number (e.g., ${}_{}{}^4{}_{}{}^{}$${\mathit{M}}_{2\mathrm{\Sigma }}^{\mathrm{-}2\mathit{n}}$, ${}_{}{}^6{}_{}{}^{}$${\mathit{M}}_{2\mathrm{\Lambda }2\mathrm{\Xi }}^{\mathrm{-}2\mathit{n}}$) could be formed in rare events. Such negative nuclei can easily be identified in a magnetic spectrometer. They could be considerably more abundant than antinuclei of the same A. We use the relativistic meson-baryon field theory—which gives an excellent description of normal nuclear and single-Λ hypernuclear properties—to calculate the rich spectrum of such exotic objects, their stability, and their structure. We also find solutions for a large variety of bound short-lived nuclei (e.g., ${}_{}{}^8{}_{}{}^{}$${\mathit{M}}_{2\mathrm{\Lambda },2\mathrm{}\mathrm{\Sigma }}^{\mathrm{-}2\mathit{p}2\mathit{n}}$), which may decay strongly via formation of cascade (Ξ) particles. Multi-Ξ hypernuclei are also evaluated. A variety of potential candidates for such metastable exotic nuclei is presented. It turns out that the properties of such exotic multihypernuclear objects reveal quite similar features as the strangelet proposed as a unique signature for quark-gluon plasma formation in heavy ion collisions.

We calculate the transverse-mass distribution of lepton pairs in the ${\mathrm{\rho }}^0$-ω peak. We use two different ultrarelativistic nuclear collision scenarios: one with a strong first-order deconfinement phase transition, and one with a first-order chiral phase transition. In both cases, we assume thermal and chemical equilibrium throughout the collision, and consider transition temperatures in the range 150–200 MeV. We then follow the experimental procedure and fit the transverse-mass distribution with a thermal distribution. The fitting temperature is near the transition temperature for both scenarios.

We obtain a mean-field solution for the nucleon as a quark-meson soliton obtained from the action of the global color-symmetry model of QCD. All dynamics is generated from an effective interaction of quark currents. At the quark-meson level there are two novel features: (1) absolute confinement is produced from the space-time structure of the dynamical self-energy in the vacuum quark propagator; and (2) the related scalar meson field is an extended q¯q composite that couples nonlocally to quarks. The influence of these features upon the nucleon mass contributions and other nucleon properties is presented.