Velocity correlations of intermediate mass fragments (IMF), produced in collisions of Au+Au at 100, 150, 250, and 400A MeV beam energy, are extracted from measurements with the 4π detector system (FOPI) in construction stage I at Schwerionen-Synchrotron (SIS) at the Gesellschaft für Schwerionenforschung (GSI) in Darmstadt. The IMF correlation functions of peripheral and semicentral events are found to be strongly affected by the collective sideward motion of nuclear matter. The sideflow causes an enhancement of correlations at small relative velocities. This enhancement results from the mixing of differently azimuthally oriented events; it vanishes if the events are rotated into a unique reaction plane. Selecting violent central collisions, the comparison of the data with a Coulomb dominated final-state interaction model points to a radius of the expanding and multifragmenting source of ${\mathit{R}}_{\mathit{s}}$≃13 fm for 100A MeV which appears shrinking by 20% when increasing the projectile energy to 400 MeV per nucleon. The deduced source radii are found to depend on the radial explosion energy used in the model. The inclusion of such a collective expansion is necessary for a reasonable description of the experimental single-particle spectra of the IMF. The unique Coulomb suppression of small relative IMF velocities, found for the given beam energy range, is attributed to rather constant averaged next-neighbor distances 〈${\mathit{d}}_{\mathrm{IMF}}$〉=8.6±0.2 fm of the IMF charge centers within the source at breakup time.

An integral formula is derived for calculating the complete expansion of the Glauber amplitude of multiple scattering between two composite particles under the cluster structure, when the density function is of the form of the double Gaussian type.

We present new data for the γp→ηp reaction at average photon energies of 729 and 753 MeV. The reaction is believed to be dominated by intermediate states of ${\mathit{N}}^{\mathrm{*}}$ resonances and should be an excellent way to study the internal structure of the baryon states. Previously published data were consistent with a dominance of the ${\mathit{S}}_{11}$(1535)${\mathit{N}}^{\mathrm{*}}$ resonance intermediate states in the reaction mechanism. The new data show deviations from this picture for the first time.

An exactly solvable model is used to investigate the assumptions behind color transparency.

A diagrammatic approach to quark exchange processes in meson-meson scattering is applied to the case of inelastic reactions of the type (QQ¯)+(qq¯)→(Qq¯)+(qQ¯), where Q and q refer to heavy and light quarks, respectively. This string-flip process is discussed as a microscopic mechanism for charmonium dissociation (absorption) in hadronic matter. The cross section for the reaction J/ψ+π→D+D¯ is calculated using a potential model, which is fitted to the meson mass spectrum. The temperature dependence of the relaxation time for the J/ψ distribution in a homogeneous thermal pion gas is obtained. The use of charmonium for the diagnostics of the state of hot hadronic matter produced in ultrarelativistic nucleus-nucleus collisions is discussed.

Charged-current cross sections are calculated for quasielastic neutrino and antineutrino scattering using a relativistic meson-nucleon model. We examine how nuclear-structure effects, such as relativistic random-phase-approximation (RPA) corrections and momentum-dependent nucleon self-energies, influence the extraction of the axial form factor of the nucleon. RPA corrections are important only at low-momentum transfers. In contrast, the momentum dependence of the relativistic self-energies changes appreciably the value of the axial-mass parameter ${\mathit{M}}_{\mathit{A}}$ extracted from dipole fits to the axial form factor. Using Brookhaven’s experimental neutrino spectrum we estimate the sensitivity of ${\mathit{M}}_{\mathit{A}}$ to various relativistic nuclear-structure effects.

The center of mass (CM) of a few-body quantum system with a central field is discussed. If the particles are in the designative eigenstates, the CM coordinates of the system can be well defined. In the CM bag model as well as in other models with central fields, the CM-freedom separation rule and effective nucleon electromagnetic currents can be presented without any undetermined parameter.

Using a self-consistent quark model for nuclear matter we investigate variations of the masses of the nonstrange vector mesons, the hyperons, and the nucleon in dense nuclear matter (up to four times the normal nuclear density). We find that the changes in the hadron masses can be described in terms of the value of the scalar mean field in matter. The model is then used to calculate the density dependence of the quark condensate in-medium, which turns out to be well approximated by a linear function of the nuclear density. Some relations among the hadron properties and the in-medium quark condensate are discussed.

Internal bremsstrahlung spectrum associated with electron-capture decay of ${}_{}{}^{55}{}_{}{}^{}\mathrm{Fe}$ was measured using a HPGe detector to search for the presence of a heavy neutrino in the mass range 5–30 keV. A 17-keV neutrino with ${\sin }^2$θ≥0.007 has been excluded at the 5σ confidence level.

We have performed a search for a 17-keV neutrino in the internal bremsstrahlung spectrum accompanying the electron capture decay of ${}_{}{}^{71}{}_{}{}^{}\mathrm{Ge}$ by using an ultra-large-size HpGe detector. Special attention was paid to get the well-producing response function, the accurate peak-detection efficiency, and the appropriate counting condition in which the pileup effect can be almost negligible. All these made it possible to compare the experimental spectrum with the theoretical one without using any shape factor or smooth function. We excluded the possibility of the 17-keV neutrino with mixing fraction of (1.6±0.8)% obtained by Žlimen et al. Our upper limit for the mixing fraction of the 17-keV neutrino was estimated to be 0.6% at 95% confidence level with Q=232.${65}_{\mathrm{-}0.24}^{+0.34\mathrm{}}$ keV.

We measured the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$(α,γ) cross section at ${\mathrm{\theta }}_{\gamma }$=90° across the 16.6 and 16.9 MeV resonances in ${}_{}{}^8{}_{}{}^{}\mathrm{Be}$ and obtained angular distributions on the peaks of both resonances. The decays of the 16 MeV doublet to the 3.0 MeV $2^{+}$ final state have an (isovector E2)/(isovector M1) mixing ratio of (0.01±0.03), an (isoscalar E2)/(isovector M1) mixing ratio of (0.21±0.04), and an isovector M1 width of (2.80±0.18) eV. Our result for the isovector E2 strength disagrees markedly with previous work. We observe ground-state E2 decays of both members of the doublet. We use our results, plus existing ${}_{}{}^8{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ β-decay data, to test the conservation of the vector current and to constrain the second-class induced-tensor form factor. Finally, we compare our results to shell-model calculations.

We present some preliminary calculations on cross sections for the breakup of ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ around 100 MeV/nucleon with emphasis on the effect of nuclear breakup on the angular distributions. Underlying the results of these calculations, the possibilities and problems of extracting the astrophysical S factor for the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(α,γ${)}^{16}$O reaction at very low energies are discussed. Some considerations on the experimental conditions for a ${}_{}{}^{16}{}_{}{}^{}\mathrm{O}$ breakup experiment aiming at this astrophysical information are given.

The emission of light fragments with energies ≥1A MeV from asymmetric ${}_{}{}^{14}{}_{}{}^{}\mathrm{N}$ induced reactions at 14A MeV and 32A MeV has been studied. The overall energy- and angular dependence of the isobaric ${}_{}{}^3{}_{}{}^{}\mathrm{H}$${/}^3$He and ${}_{}{}^6{}_{}{}^{}\mathrm{He}$${/}^6$Li ratios is understood in terms of standard statistical emission processes from an incomplete fusion source and an intermediate source only if the effective Coulomb barriers are reduced much more than the normal quantum penetration accounts for.

Evidence for hexadecapole collectivity in closed-shell nuclei is presented by examining the observed characteristics of the lowest $4^{+}$ excited state in each case. These $4^{+}$ states, presently identified in the N=82 isotones ${}_{}{}^{132}{}_{}{}^{}\mathrm{Sn}$ and ${}_{}{}^{140}{}_{}{}^{}\mathrm{Ce}$, and the Z=82 isotopes, ${}_{}{}^{202}{}_{}{}^{}\mathrm{Pb}$ and ${}_{}{}^{204}{}_{}{}^{}\mathrm{Pb}$, have nanosecond half-lives, and are found to decay by enhanced E4 transitions to the respective $0^{+}$ ground state, whereas ΔI=2 E2 transitions from, and to, these states have B(E2) values which are only a fraction of a Weisskopf unit. These features, suggestive of a significant one-phonon hexadecapole component in the structure of these $4^{+}$ states, are interpreted in terms of their shell model configurations. Similar characteristics are predicted for some other closed-shell nuclei.

Reported measurements of the intensity ratio of the 674.04 and 1379.40 keV γ rays from the 1460 keV $0^{+}$ level in ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ differ by a factor of 10. This difference is resolved by a new measurement which produces a ratio of 0.024±0.003, in agreement with the majority of measurements. This ratio is important in assessing the two-phonon or β-vibrational nature of the lowest excited K=$0^{+}$ band, at 1460 keV, and confirms that its properties differ from those found in the majority of deformed rare earth nuclei.

A new rotational band has been observed via the reaction of ${}_{}{}^{28}{}_{}{}^{}\mathrm{Si}$ bombarding a ${}_{}{}^{92}{}_{}{}^{}\mathrm{Mo}$ target at beam energies of 100–120 MeV with an array consisting of 7 BGO(AC) HPGe detectors and a 14-element BGO ball. The band is most likely the π${\mathit{h}}_{11/2}$ band of ${}_{}{}^{117}{}_{}{}^{}\mathrm{Cs}$, a nucleus for which no excited states were previously known. The systematic properties of the π${\mathit{h}}_{11/2}$ bands in odd-A Cs nuclei from A=117 to 127 have been reproduced by particle-plus-triaxial rotor model calculations. The good agreement with experiment suggests that the β deformation is strongly dependent on the number of neutrons while the γ deformation stays rather constant for all of these odd-mass Cs nuclei.

Large discrepancies have been reported between the Gamow-Teller strengths determined from ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ β-delayed proton decay, and the isospin-analog strengths deduced from ${}_{}{}^{37}{}_{}{}^{}\mathrm{Cl}$(p,n) studies. Some of these discrepancies could be removed if the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ daughter level at 3.24 MeV in ${}_{}{}^{37}{}_{}{}^{}\mathrm{K}$ had ${\mathrm{\Gamma }}_{\gamma }$ forty times bigger than its ${\mathrm{\Gamma }}_{\mathit{p}}$, and not negligibly small as assumed in the initial analysis of the ${}_{}{}^{37}{}_{}{}^{}\mathrm{Ca}$ β decay. We studied proton and γ-ray branching ratios of low-lying ${}_{}{}^{37}{}_{}{}^{}\mathrm{K}$ levels populated via the ${}_{}{}^{40}{}_{}{}^{}\mathrm{Ca}$(p,α) reaction. We find that the 3.24 MeV level has ${\mathrm{\Gamma }}_{\gamma }$/${\mathrm{\Gamma }}_{\mathit{p}}$>8, and that the 2.75 and 3.08 MeV levels have ${\mathrm{\Gamma }}_{\gamma }$/${\mathrm{\Gamma }}_{\mathit{p}}$=0.52±0.23 and ${\mathrm{\Gamma }}_{\gamma }$/${\mathrm{\Gamma }}_{\mathit{p}}$=0.41±0.014, respectively. In addition we identified new ${}_{}{}^{37}{}_{}{}^{}\mathrm{K}$ levels at ${\mathit{E}}_{\mathit{x}}$=3.272±0.002 and 2.967±0.002 MeV.

High-spin states in the N=51 nucleus ${}_{}{}^{94}{}_{}{}^{}\mathrm{Tc}$ have been investigated with γ-ray spectroscopic techniques following the reactions ${}_{}{}^{66}{}_{}{}^{}\mathrm{Zn}$${(}^{31}$P,2pn${)}^{94}$Tc and ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}$${(}^{36}$S,α3n${)}^{94}$Tc. Shell-model calculations have been performed. The excitation of a single neutron across the N=50 core adequately describes the observed high-spin states in ${}_{}{}^{94}{}_{}{}^{}\mathrm{Tc}$.

The asymmetric fission barriers and the released kinetic energies in the deformation valley leading rapidly to two tangent spherical fragments have been calculated for ${}_{}{}^{194}{}_{}{}^{}\mathrm{Hg}$, ${}_{}{}^{149}{}_{}{}^{}\mathrm{Tb}$, ${}_{}{}^{110\mathrm{-}112}{}_{}{}^{}\mathrm{In}$, ${}_{}{}^{94}{}_{}{}^{}\mathrm{Mo}$, and ${}_{}{}^{75}{}_{}{}^{}\mathrm{Br}$ within the generalized liquid-drop model including the nuclear proximity energy. Results are compared to experimental data and predictions of the Yukawa plus exponential finite range liquid-drop model and the liquid-drop model. The calculated asymmetric fission barrier heights lie between the values obtained by the two other theoretical approaches.

Shell-model calculations suggest that binding energies of several proton-rich nuclei in the vicinity of ${}_{}{}^{100}{}_{}{}^{}\mathrm{Sn}$ differ appreciably from the estimates given in the most recent Mass Tables. We give improved estimates, which should be of considerable interest to researchers at GSI and elsewhere who are studying β-decay and β-delayed proton emission from these nuclei.