The hypernuclear Auger effect, given by the deexcitation of a Λ hypernucleus by means of the transition of a Λ hyperon from an initial to a lower lying final single particle state in conjunction with neutron emission from the core nucleus is studied in density dependent relativistic hadron field theory. Baryonic interactions are obtained from the Bonn potential by Dirac-Brueckner theory and theoretically derived scaling laws for the meson-hyperon vertices. The model is applied to the ${}_{\hspace{0.5em}\Lambda }^{209}\mathrm{Pb}$ hypernucleus. Λ and nucleon bound states, as well as scattering states, are calculated self-consistently in mean-field approximation. The Auger spectra of the emitted neutrons are of complex structure due to a huge combinatorial number of possible hypernuclear transitions. The sensitivity of the neutron Auger spectra to changes in the Λσ and Λω vertices is investigated. The theoretical results show that experimental applications of the hypernuclear Auger effect will require special efforts, e.g., by tagging on the energy of the initially created hyperon.

Variational calculations of nucleon matter, either symmetric nuclear or pure neutron matter, use Fermi hypernetted chain and single-operator chain summation methods to sum approximately the contributions of clusters of $>~3$ nucleons to the energy expectation value. The cluster contributions summed by these methods are discussed in detail, and it is shown that for realistic interactions the 3-body cluster contribution is larger than the sum of $>~4$-body contributions. We present a new method, based on representing cluster wave functions by multidimensional vectors in spin-isospin space, as is common in quantum Monte Carlo calculations of light nuclei, to calculate exactly the 3-body cluster contribution including 3-body forces and all but spin-orbit correlations. The variational energies obtained with the Argonne $v18\mathrm{}$ 2- and Urbana IX 3-nucleon interactions, using the exact 2- and 3-body cluster contributions and the approximate $>~4$-body contributions summed with chain summation techniques are lower, closer to the empirical values for symmetric nuclear matter than in previous calculations using the operator chain summation approximation for the large 3-body cluster. In pure neutron matter the operator chain summation approximation is found to be fairly accurate for the 3-body cluster; the present results are only slightly higher than the previous ones. We also report on the results for the Argonne $v14\mathrm{}$ 2-nucleon interaction without any 3-body interaction. This case has been studied with Brueckner’s method including 2, 3, and parts of 4-hole line terms by Day and Wiringa [Phys. Rev. C 32, 1057 (1985)]. Our results are significantly lower than theirs.

The nuclear decay of ${}_{75}^{179}\mathrm{Re}$ has been studied following the ${}^{165}\mathrm{Ho}{(}^{18}\mathrm{O}{,4n)}^{179}\mathrm{Re}$ and ${}^{173}\mathrm{Yb}{(}^{11}\mathrm{B}{,5n)}^{179}\mathrm{Re}$ reactions. Previously unobserved multiquasiparticle states have been identified in ${}_{75}^{179}\mathrm{Re},$ with highly K-forbidden decays. One of these, with a half-life of 466±15 μs, is the longest-lived high-seniority (>6) isomer yet discovered. This metastable state offers an opportunity to explore K isomerism as protons are added away from the midshell region. In addition, the excitation energies of several previously “floating” bands have been determined. Energies, lifetimes, configuration assignments, and g factors are discussed and compared to predictions of blocked BCS calculations.

Excited states of ${}^{156}\mathrm{Dy}$ were populated through ${\beta }^{+}/\varepsilon$ decay and studied through γ-ray spectroscopy at the Yale Moving Tape Collector. Extensive data led to improved information on the electromagnetic decay properties of low-spin states and to a substantially revised level scheme. The structural observables of ${}^{156}\mathrm{Dy}$ are compared with those of the other nearby $N=90\mathrm{}$ isotones and to predictions of the $X\left(5\right)\mathrm{}$ model for nuclei in the spherical-deformed transition region.

Excited states in the neutron-deficient isotope ${}^{169}\mathrm{Os}$ have been identified for the first time in an experiment using the Jurosphere $\gamma$-ray spectrometer in conjunction with the Ritu gas-filled recoil separator. The problems associated with identifying neutron-deficient isotopes produced with low fusion cross sections against a high background of competing channels, including fission, have been overcome by using the recoil-decay tagging technique. The band structures observed in ${}^{169}\mathrm{Os}$ are interpreted in the context of the systematics of neighboring nuclei and the predictions of cranked Woods-Saxon calculations. The systematics of the second ${(i}_{13/2}{)}^2$ neutron alignment in this region are discussed.

We consider a single state stochastically coupled to its stochastic background states which are generated by the Gaussian orthogonal ensemble of random matrices. The strength function of the single state is investigated systematically when the dimension of the random matrices is finite. As the finite size effects, the double-peak distribution and transition of the strength function from a squeezed-Breit-Wigner to a ladder-shaped distribution are found and analyzed. Meanwhile the domain for validity of the Breit-Wigner distribution is given.

In certain neutron-rich Te isotopes, a decrease in the energy of the first excited $2^{+}$ state is accompanied by a decrease in the $E2\mathrm{}$ strength to that state from the ground state, contradicting simple systematics and general intuition about quadrupole collectivity. We use a separable quadrupole-plus-pairing Hamiltonian and the quasiparticle random phase approximation to calculate energies, ${B(E2,0\mathrm{}}^{+}\to 2^{+})$ strengths, and g factors for the lowest $2^{+}$ states near ${}^{132}\mathrm{Sn}$ $(Z>~50).$ We trace the anomalous behavior in the Te isotopes to a reduced neutron pairing above the $N=82\mathrm{}$ magic gap.

Natural tellurium has been activated with thermal neutrons $(kT=22\mathrm{}\mathrm{meV})$ and with quasistellar neutrons $(kT=25\mathrm{}\mathrm{keV}).\mathrm{}$ By analyzing the ground state decay of the odd isotopes as a function of time, information on the partial capture cross sections to the isomeric states could be determined with systematic uncertainties of 3–8 %. Additionally, the decay parameters of some isomers could be significantly improved. These results are of relevance for s-process nucleosynthesis.

The semiexclusive reaction ${}^4\mathrm{He}({\pi }^{+},{\pi }^{-}pp)pp$ has been studied at pion kinetic energies of 105 MeV and 115 MeV. Signatures from the production of the hypothetical $\pi \mathrm{NN}$ resonance $d^{\prime }$ have been searched for in the invariant mass $M_{\pi \mathrm{pp}}$ spectra. No hint for a dominant $d^{\prime }$ production, as anticipated from double charge exchange excitation functions on nuclei, has been found. The data are satisfactorily described by sequential single charge exchange.

The ${}^{16}\mathrm{O}{+}^{58}\mathrm{Ni}$ deep-inelastic collision has been investigated at $E_{\mathrm{lab}}{(}^{16}\mathrm{O})=132\mathrm{}\mathrm{MeV}$ by using coincident charged particle techniques. Exclusive data of the projectilelike fragments (C, N, and O) and their associated light charged particles (protons and $\alpha$ particles) were collected in coincidence. The experiment has been performed at the IReS Strasbourg VIVITRON Tandem facility by using the ICARE charged particle multidetector array. The measured velocity diagrams and in-plane angular correlations have been analyzed by a semiclassical model that combines equilibrium and nonequilibrium processes of a deep-inelastic scattering reaction. Following the hypothesis of a sequential process, this closed-form theoretical approach is applied to the measured $\left[\right(\mathrm{C},\mathrm{N},\mathrm{O})-p]$ and $\left[\right(\mathrm{C},\mathrm{N},\mathrm{O})-\alpha ]$ differential multiplicities. Estimates on polarization phenomena and on “decay times” are used to provide information about deep-inelastic scattering in ${}^{16}\mathrm{O}{+}^{58}\mathrm{Ni}$ at 8.25 MeV/nucleon.

Measurements of charged pion and kaon production in central Pb+Pb collisions at 40, 80, and 158 A GeV are presented. These are compared with data at lower and higher energies as well as with results from $p+p$ interactions. The mean pion multiplicity per wounded nucleon increases approximately linearly with $s_{\mathrm{NN}}^{1/4}$ with a change of slope starting in the region 15–40 A GeV. The change from pion suppression with respect to $p+p$ interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40A GeV. A nonmonotonic energy dependence of the ratio of $K^{+}$ to ${\pi }^{+}$ yields is observed, with a maximum close to 40A GeV and an indication of a nearly constant value at higher energies. The measured dependences may be related to an increase of the entropy production and a decrease of the strangeness to entropy ratio in central Pb+Pb collisions in the low SPS energy range, which is consistent with the hypothesis that a transient state of deconfined matter is created above these energies. Other interpretations of the data are also discussed.

The amount of proton stopping in central Pb+Pb collisions from 20–160 A GeV as well as hyperon and antihyperon rapidity distributions are calculated within the UrQMD model in comparison to experimental data at 40, 80, and 160 A GeV taken recently from the NA49 collaboration. Furthermore, the amount of baryon stopping at 160A GeV for Pb+Pb collisions is studied as a function of centrality in comparison to the NA49 data. We find that the strange baryon yield is reasonably described for central collisions, however, the rapidity distributions are somewhat more narrow than the data. Moreover, the experimental antihyperon rapidity distributions at 40, 80, and 160 A GeV are underestimated by up to factors of 3—depending on the annihilation cross section employed—which might be addressed to missing multimeson fusion channels in the UrQMD model.

Based on a hydrodynamical model, we compare $130\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}$$\mathrm{Au}+\mathrm{Au}$ collisions at the Relativistic Heavy Ion Collider (RHIC) and $17\mathrm{G}\mathrm{e}\mathrm{V}/\mathrm{n}\mathrm{u}\mathrm{c}\mathrm{l}\mathrm{e}\mathrm{o}\mathrm{n}$ $\mathrm{Pb}+\mathrm{Pb}$ collisions at the Super Proton Synchrotron (SPS). The model well reproduces the single-particle distributions of both the RHIC and SPS. The numerical solution indicates that a huge amount of collision energy in the RHIC is mainly used to produce a large extent of hot fluid rather than to make a high temperature matter; the longitudinal extent of the hot fluid in the RHIC is much larger than that of the SPS and the initial energy density of the fluid is only 5% higher than the one in the SPS. The solution well describes the HBT radii at the SPS energy but shows some deviations from the ones at the RHIC.

We investigate the effect of early chemical freeze-out on radial flow, elliptic flow, and Hanbury Brown–Twiss (HBT) radii by using a fully three-dimensional hydrodynamic model. When we take account of the early chemical freeze-out, the space-time evolution of temperature in the hadron phase is considerably different from the conventional model in which chemical equilibrium is always assumed. As a result, we find that radial and elliptic flows are suppressed and that the lifetime and the spatial size of the fluid are reduced. We analyze the $p_t$ spectrum, the differential elliptic flow, and the HBT radii at the Relativistic Heavy-Ion Collider energy by using hydrodynamics with a chemically nonequilibrium equation of state.

Two-pion correlation functions are analyzed at midrapidity for three systems $(14.6A\mathrm{GeV}/c$ Si+Al, Si+Au, and $11.6A\mathrm{GeV}/c$ Au+Au), seven distinct centrality conditions, and different $k_T$ bins in the range 0.1–0.5 GeV/c. Source reference frames are determined from fits to the Yano-Koonin source parametrization. Bertsch-Pratt radius parameters are shown to scale linearly with both number of projectile and total participants as obtained from a Glauber model calculation. A finite lifetime parameter that increases linearly with system/centrality is also reported. The $m_T$ dependences of the Bertsch-Pratt radii for the central Si+Au and central Au+Au systems differ only by an overall normalization factor given by the measured system/centrality dependence.

A general shell model formalism for the nonmesonic weak decay of the hypernuclei has been developed. It involves a partial wave expansion of the emitted nucleon waves, preserves naturally the antisymmetrization between the escaping particles and the residual core, and contains as a particular case the weak Λ-core coupling formalism. The extreme particle-hole model and the quasiparticle Tamm-Dancoff approximation are explicitly worked out. It is shown that the nuclear structure manifests itself basically through the Pauli principle, and a very simple expression is derived for the neutron- and proton-induced decays rates ${\Gamma }_n$ and ${\Gamma }_p,$ which does not involve the spectroscopic factors. We use the standard strangeness-changing weak $\Lambda \overrightarrow{N}\mathrm{NN}$ transition potential which comprises the exchange of the complete pseudoscalar and vector meson octets $(\pi ,\eta ,K,\rho ,\omega {,K}^{*}),$ taking into account some important parity-violating transition operators that are systematically omitted in the literature. The interplay between different mesons in the decay of ${}_{\Lambda }^{12}C$ is carefully analyzed. With the commonly used parametrization in the one-meson-exchange model (OMEM), the calculated rate ${\Gamma }_{\mathrm{NM}}={\Gamma }_n+{\Gamma }_p$ is of the order of the free Λ decay rate ${\Gamma }^0\left({\Gamma }_{\mathrm{NM}}^{\mathrm{th}}\cong {\Gamma }^0\right)$ and is consistent with experiments. Yet the measurements of ${\Gamma }_{n/p}={\Gamma }_n/{\Gamma }_p$ and of ${\Gamma }_p$ are not well accounted for by the theory $({\Gamma }_{n/p}^{\mathrm{th}}\lesssim 0.42,{\Gamma }_p^{\mathrm{th}}\gtrsim 0.60{\Gamma }^0).\mathrm{}$ It is suggested that, unless additional degrees of freedom are incorporated, the OMEM parameters should be radically modified.

The possibility of the determination of the neutron mean square charge radius from high-precision thermal-neutron measurements of the nuclear scattering length and of the scattering amplitudes of Bragg reflections is considered. Making use of the same Pendellösung technique as Shull [Phys. Rev. Lett. 21, 1585 (1968)], the scattering amplitudes of about eight higher-order Bragg reflections in silicon could be measured without single-scattering contamination. This would provide a value of the neutron charge radius as precise as the disagreeing Argonne-Garching and Dubna values, as well as a Debye-Waller factor of silicon ten times more precise than presently available.

We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states $\gamma N,$ $\pi N,$ $2\pi N,$ $\eta N,$ $K\Lambda ,$ $K\Sigma ,$ and $\omega N$ for energies from the nucleon mass up to $\sqrt{s}=2\mathrm{}$ GeV. In this analysis we find strong evidence for the resonances $P_{31}\mathrm{}\left(1750\right),$ $P_{13}\mathrm{}\left(1900\right),$ $P_{33}\mathrm{}\left(1920\right),$ and $D_{13}\mathrm{}\left(1950\right).$ The $\omega N$ production mechanism is dominated by large $P_{11}\mathrm{}\left(1710\right)\mathrm{}$ and $P_{13}\mathrm{}\left(1900\right)\mathrm{}$ contributions. In this first part, we present the results of the pion-induced reactions and the extracted resonance and background properties with emphasis on the difference between global and purely hadronic fits.

We present a nucleon resonance analysis by simultaneously considering all pion- and photon-induced experimental data on the final states $\gamma N,$ $\pi N,$ $2\pi N,$ $\eta N,$ $K\Lambda ,$ $K\Sigma ,$ and $\omega N$ for energies from the nucleon mass up to $\sqrt{s}=2\mathrm{}\mathrm{GeV}.$ In this analysis we find strong evidence for the resonances $P_{31}\mathrm{}\left(1750\right),$ $P_{13}\mathrm{}\left(1900\right),$ $P_{33}\mathrm{}\left(1920\right),$ and $D_{13}\mathrm{}\left(1950\right).$ The $\omega N$ production mechanism is dominated by large $P_{11}\mathrm{}\left(1710\right)\mathrm{}$ and $P_{13}\mathrm{}\left(1900\right)\mathrm{}$ contributions. In this second part we present the results on the photoproduction reactions and the electromagnetic properties of the resonances. The inclusion of all important final states up to $\sqrt{s}=2\mathrm{}\mathrm{GeV}$ allows for estimates on the importance of the individual states for the GDH sum rule.

A partial-wave analysis of single-pion photoproduction data has been completed. This study extends from threshold to 2 GeV in the laboratory photon energy, focusing mainly on the influence of new measurements and model dependence in the choice of parametrization employed above the two-pion threshold. Results are used to evaluate sum rules and estimate resonance photodecay amplitudes. These are compared to values obtained in the MAID analysis.