Rajagopal and Wilczek have proposed that relativistic nuclear collisions can generate domains in which the chiral condensate is disoriented. If sufficiently large (i.e., nucleus sized), such domains can yield measurable fluctuations in the number of neutral and charged pions. However, by numerical simulation of the zero-temperature two-flavor linear sigma model, we find that domains are essentially pion sized. Nevertheless, we show that large domains can occur if the effective mesons masses are much lighter.

We develop a detailed theory for multiphonon excitation in heavy-ion collisions. This theory fully accounts for the effects of the finite lifetimes of the states involved and allows the treatment of both formation and decay of multiphonon states through explicit consideration of spreading and escape widths. A schematic model is used to study the influence of the widths on the formation cross sections. We find that the finite width of the one-phonon resonance leads to a decrease in the two-phonon state cross section.

The nucleon-nucleon potential obtained from the most general effective chiral Lagrangian involving low momentum pions, nonrelativistic nucleons, and Δ isobars was considered to third order in the chiral expansion. The parameters of the potential were adjusted to reproduce the low energy nucleon-nucleon scattering phase shifts as well as the properties of the deuteron. Reasonable fits are obtained in this first application of a nucleon-nucleon potential based on chiral symemtry.

The cross section for quasielastic ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(e,e’p) scattering has been measured at momentum transfer ${\mathit{Q}}^2$=1, 3, 5, and 6.8 (GeV/c${)}^2$. The results are consistent with scattering from a single nucleon as the dominant process. The nuclear transparency is obtained and compared with theoretical calculations that incorporate color transparency effects. No significant rise of the transparency with ${\mathit{Q}}^2$ is observed.

A new region characterized by Lévy diffusion exists in collective motion between the adiabaic and diabatic limits. Repeated chaotic scattering off of level crossings, whose repulsive or attractive nature changes dynamically, can result in localization of the collective motion for arbitrarily periods of time, and anomalous diffusion.

The ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(e,e’x) reaction has been investigated for excitation energies between 8 and 26 MeV and momentum transfers from 0.25 to 0.66 ${\mathrm{fm}}^{\mathrm{-}1}$ at the continuous-wave electron accelerators MAMI at Mainz S-DALINAC at Darmstadt. A multipole decomposition of the cross sections reveals strongly fragmented E2 (plus E0) strength around 14 and 17 MeV in contrast to all theoretical predictions. Angular correlations of proton decay are described over the entire energy range by a continuum random-phase-approximation approach. A comparison of the branching ratios to statistical model calculations provides information on the dominant damping mechanism.

The discovery of the new proton emitter ${}_{}{}^{112}{}_{}{}^{}\mathrm{Cs}$ with an energy of 807±7 keV and a half-life of 500±100 μs is reported. WKB half-life calculations indicate ${\mathit{d}}_{5/2}$ proton emission with a low spectroscopic factor comparable to values for ${}_{}{}^{109}{}_{}{}^{}\mathrm{I}$ and ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cs}$. This behavior is consistent with the onset of deformation in this region. The odd-odd nuclides ${}_{}{}^{112}{}_{}{}^{}\mathrm{Cs}$ and ${}_{}{}^{108}{}_{}{}^{}\mathrm{I}$ have significantly lower ${\mathit{Q}}_{\mathit{p}}$ values than the corresponding isotopes lying closer to stability, which is attributed to strong pairing forces between the odd nucleons. The half-life of ${}_{}{}^{113}{}_{}{}^{}\mathrm{Cs}$ has been measured with improved precision as 17±2 μs.

We study chiral symmetry breaking in nuclear matter. For the dynamics we use a class of quark models with a chiral invariant confining potential. The mass gap equation is obtained when we minimize the energy of the matter with respect to the chiral angle φ and to the quark wave function in the nucleon. At low nuclear density ρ, we find that the chiral angle decreases slightly, the nucleon swells and the nucleon mass decreases. However, for the density of nuclear matter, we find that the chiral angle suffers an enhancement. We briefly discuss the physical consequences of this effect and its independence of the microscopic quark model.

Multifragmentation of the system α${+}^{197}$Au has been studied at incident energies of 1 and 3.6 GeV/nucleon with the new 4π setup, FASA. Mass, energy, and velocity of a few fragments are measured with high precision using time-of-flight telescopes, while for the other fragments, global multiplicity information is obtained from 55 CsI(Tl) detectors covering the main part of 4π. Very high mean IMF (intermediate mass fragment) multiplicities of 〈M${\mathrm{〉}}_{\mathrm{IMF}}$=5.1±0.8 are observed at the higher incident energy. Compared to the lower incident energy, they increase by 40%, indicating an increasing energy deposition with increasing incident energy.

We present data on hard-photon production in ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$${+}^{197}$Au and ${}_{}{}^{36}{}_{}{}^{}\mathrm{Ar}$${+}^{12}$C collisions at 95 MeV/nucleon. The photon source velocity ${\mathrm{\beta }}_{\mathit{S}}$ is investigated as a function of system size, photon energy, and impact parameter. In the heavy system, ${\mathrm{\beta }}_{\mathit{S}}$ is found to be sizably smaller than ${\mathrm{\beta }}_{\mathrm{beam}}$/2, except for very peripheral reactions. This unambiguously demonstrates that at intermediate bombarding energies photon emission is not solely dominated by first-chance p-n collisions, but carries also information on the later, stopping phase of the reaction.

Sub-eV Majorana neutrino masses 〈${\mathit{m}}_{\nu }$〉, can be explored by a new approach to neutrinoless double β decay using ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$ in a Xe gas-loaded, multiton liquid scintillator installed in a very low background detector such as the Kamiokande facility. With enriched ${}_{}{}^{136}{}_{}{}^{}\mathrm{Xe}$, a readily implementable, 10 ton detector experiment can establish an 〈${\mathit{m}}_{\nu }$〉=0.45 eV at 3σ in 1 yr (or exclude an 〈${\mathit{m}}_{\nu }$〉<0.23 eV in 2 yr). A 100 ton detector can extend the limit to 〈${\mathit{m}}_{\nu }$〉<0.1 eV, compared with the present limit of 〈${\mathit{m}}_{\nu }$〉<1.3 eV.

A search for new massive particles with a low charge to mass ratio in S-W collisions at a beam momentum of 200 GeV/c per nucleon is presented. Upper limits for the production of strangelets with a mass to charge ratio of up to 60 GeV/${\mathit{c}}^2$ at rigidities of ±150 GV are reported.

The transverse momentum and rapidity distributions of negative hadrons and participant protons have been measured for central ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$+ ${}_{}{}^{32}{}_{}{}^{}\mathrm{S}$ collisions at ${\mathit{p}}_{\mathrm{lab}}$=200 GeV/c per nucleon. The proton mean rapidity shift 〈Δy〉∼1.6 and mean transverse momentum 〈${\mathit{p}}_{\mathit{T}}$〉∼0.6 GeV/c are much higher than in pp or peripheral AA collisions and indicate an increase in the nuclear stopping power. All ${\mathit{p}}_{\mathit{T}}$ spectra exhibit similar source temperatures. Including previous results for ${\mathit{K}}_{\mathit{s}}^0$ Λ, and Λ¯, we account for all important contributions to particle production.

We have confirmed the 1974 report of the discovery of element 106 by Ghiorso et al. The 0.9-s ${}_{}{}^{263}{}_{}{}^{}106$ was produced at the Lawrence Berkeley Laboratory 88-Inch Cyclotron via the ${}_{}{}^{249}{}_{}{}^{}\mathrm{Cf}$${(}^{18}$O,4n${)}^{263}$106 reaction using a beam of 95-MeV ${}_{}{}^{18}{}_{}{}^{}\mathrm{O}$ ions. Positive identification of ${}_{}{}^{263}{}_{}{}^{}106$ was made by observing its α decay followed closely in time by the α decay of the ${}_{}{}^{259}{}_{}{}^{}\mathrm{Rf}$ daughter. Our rotating wheel system was used in a special parent-daughter mode with six pairs of detectors. The ${}_{}{}^{263}{}_{}{}^{}106$ half-life, α-decay energy, and production cross section are consistent with those measured by Ghiorso et al. The half-life and α-decay energies of the ${}_{}{}^{259}{}_{}{}^{}\mathrm{Rf}$ daughter events are also consistent with those previously published.

A discrete superdeformed rotational band has been discovered in ${}_{}{}^{144}{}_{}{}^{}\mathrm{Gd}$ following the reaction ${}_{}{}^{100}{}_{}{}^{}\mathrm{Mo}$${(}^{48}$Ti, 4n${)}^{144}$Gd at 221 MeV. The dynamical moment of inertia shows a sharp irregularity at ħω=0.45 MeV. The intensity of the γ-ray transitions suggests that the irregularity can be associated with a backbend, which is interpreted in terms of the N=6 proton band crossing. The experimental results are in good agreement with cranked mean field calculations, which indicate the presence of large shell gaps for both protons and neutrons.

Shell effects in nuclei close to the neutron-drip lines have been investigated. It has been demonstrated in the relativistic mean-field theory that nuclei very far from stability manifest the shell effects strongly. This behavior is in accord with the predictions of nuclear masses in the finite-range droplet model including shell corrections. The shell effects predicted in the existing Skyrme mean-field theory in comparison are significantly weaker than those of the other approaches.

We investigate the α- and γ-decay properties of states belonging to the ground state ‘‘band’’ of ${}_{}{}^{212}{}_{}{}^{}\mathrm{Po}$, using an α-cluster model with parameter values taken from an earlier study of α decay of heavy nuclei. The known lifetimes of these states, which vary from 5.5×${10}^{\mathrm{-}10}$ s to 45 s, are reproduced to within a factor of ∼2. The (approximately) known α branching ratios, which vary from 3.3×${10}^{\mathrm{-}4}$ to 0.71, are reproduced to within a factor ∼5. These results strongly suggest a large amount of α clustering in this heavy nucleus.

Fine structure has been observed in the α decay of ${}_{}{}^{202}{}_{}{}^{}\mathrm{Rn}$, ${}_{}{}^{194,196,198}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{186,188}{}_{}{}^{}\mathrm{Pb}$, and ${}_{}{}^{180,182,184}{}_{}{}^{}\mathrm{Hg}$ and has led to the identification of low-lying $0^{+}$ states in ${}_{}{}^{198}{}_{}{}^{}\mathrm{Po}$, ${}_{}{}^{190,192,194}{}_{}{}^{}\mathrm{Pb}$, ${}_{}{}^{182,184}{}_{}{}^{}\mathrm{Hg}$, and ${}_{}{}^{176,178,180}{}_{}{}^{}\mathrm{Pt}$. The large variation in the hindrance factors of the α decay to the exicted $0^{+}$ state is a proof for the persistence of the Z=82 shell closure at the neutron-deficient side. Comparing the reduced widths of the α decays to the ground and excited states offers a unique way to probe the proton particle-hole character of the $0^{+}$ states in this region.

Three rotational bands have been discovered in the nucleus ${}_{}{}^{109}{}_{}{}^{}\mathrm{Sb}$ that extend in angular momentum to ≃81/2ħ. The rotational frequency at the highest spins reaches ħω≃1.4 MeV, the highest frequency so far observed in a heavy nucleus. With increasing frequency the collective moments of inertia of all three bands smoothly diminish to unexpectedly low values, ${\mathit{scrJ}}^{\mathrm{}\left(2\right)\mathrm{}}$∼13${\mathrm{ħ}}^2$ ${\mathrm{MeV}}^{\mathrm{-}1}$, approximately one-third the rigid-body value, and, contrary to expectations, the moments of inertia become nearly equal to one another and to those of rotational bands in the core nucleus ${}_{}{}^{108}{}_{}{}^{}\mathrm{Sn}$.

The nucleus ${}_{}{}^{176}{}_{}{}^{}\mathrm{W}$ has been studied using the reaction ${}_{}{}^{150}{}_{}{}^{}\mathrm{Nd}$${(}^{30}$Si,4n), with prompt and delayed γ-γ coincidence techniques. A K=14 isomer (${\mathit{t}}_{1/2}$≊70 ns) is found to exhibit a unique decay pattern, primarily decaying to K=0 states, in contrast to all previously studied high-K isomers. Calculations have been perfomed of both Coriolis mixing and tunneling through a potential barrier in the triaxial degree of freedom to understand these unusual decays. While Coriolis mixing models do not reproduce the variations in the decay patterns in neighboring nuclei, the tunneling calculations are remarkably successful.