Table of contents

The variational cumulant expansion is extended to d-dimensional U(1) gauge theory with radially active Higgs fields in the fundamental representation. The phase structures are given for d=3 and d=4 cases. A comparison with Monte Carlo and mean field results is also presented.

The main features of the behaviour of the inelasticity and hadron spectra in the fragmentation region are derived on the basis of the modified dual parton model.

The origin of the broad structure in the ratio of the differential cross section at 0 degrees and 30 degrees CMS scattering angle in the pp to pi ⁺d process at the invariant mass of 2.41 GeV, which has been extracted using the world collection of experimental data as input, has been analysed. The observed pattern can be generated by a combination of the Pauli principle restrictions upon the helicity amplitudes combined with their individual and smooth energy behaviour. No assertions regarding additional dibaryon dynamics can be made without accounting for the observed effect. A toy model is presented solely as an illustration.

The authors review the results and techniques of experiments on the lifetime of the free neutron. The mean value is 887.4 (1.7) s at the 1 sigma confidence level. They further discuss the relevance of these results for other fields like weak interaction theory, neutrino physics, astrophysics and cosmology.

A bosonized version of the SU(2) Nambu-Jona-Lasinio model is solved self-consistently for hedgehog fields on the chiral circle in the solitonic sector with baryon number B=2. The authors consider explicitly the case in which the baryon number is raised by occupying B-bound valence quark states for different winding numbers omega of the chiral angle. It is found that only the cases B>or= omega allow the existence of self-consistent solutions. Fractional windings are also excluded in practice by the self-consistency condition. For the description of nucleon properties the constituent mass has to be chosen around 400 MeV. There no solitons with higher winding numbers are found in contrast to the results of the Skyrme model. On the other hand, in this region the binding energy of the deuteron and the alpha -particle can be roughly reproduced with winding number one.

The projected hedgehog approximation for baryons in models with interacting quarks and mesons is investigated. Exploiting the reduction of the Hilbert space to a subspace containing only one radial mode, the authors factorize matrix elements of observables into radial integrals and isospin-spin coefficients. The reduction is explicitly given for the linear sigma model. In order to analyse the quality of the hedgehog ansatz the solution obtained with the projected hedgehog coherent state in the reduced model is then compared with the solutions obtained with appropriate perturbative expansions in the weak and strong coupling limits and with the solution obtained by diagonalizing the Hamiltonian in the intermediate regime. The energy of the ground state and the expectation values of some other physically relevant operators in this approximation turn out to be in very good agreement with the values obtained with the accurate techniques.

Based on the exact three-dimensional relativistic equation for qq bound states, an off-shell retarded one-gluon exchange potential is derived and employed to calculate meson spectra. The calculated results show that the retardation effect is important for the improvement of the theoretical values of lighter meson masses.

The authors have calculated the differential cross sections and polarization observables for elastic and inelastic scattering of intermediate-energy protons on ¹²C and ¹⁶O nuclei on the basis of the multiple diffraction scattering theory with the nucleon density and transition density obtained from the alpha -cluster model with dispersion and from model-free analysis. They have shown that there is a qualitative difference between the elastic scattering spin-rotation functions calculated by the alpha -cluster model with dispersion and by the independent-nucleon model.

High spin states in the odd proton nucleus ¹²⁹La have been investigated using the techniques of in-beam gamma -ray spectroscopy. Nine rotational bands have been observed in ¹²⁹La, seven for the first time. Various band crossings were observed at rotational frequencies in the range h(cross) omega =0.28-0.57 MeV. The data are mainly discussed within the framework of the cranked shell model. The rotational bands are assigned quasiparticle configurations originating from pi h_11/2, pi g_7/2, pi (h_11/2)²(X) pi g_7/2 and pi _11/2 (X) nu (h_11/2g_7/2) states, respectively. Four of the band crossings are thought to be associated with the rotational alignments of the first pair of h_11/2 neutrons or protons.

The Doppler shift attenuation method has been used to extract the mean quadruple moment of the nu i_13/2 intruder band in ¹³⁹Gd. From a centroid-shift analysis of the data, and using Braune stopping powers, a value for the intrinsic nuclear quadrupole moment of Q₀ approximately=7.0 eb is suggested, corresponding to a deformation beta ₂ approximately=0.35. Because of appreciable side-feeding into the band at each level, a lineshape analysis of the data has also been attempted, in which the time structure of the side-feeding has been allowed to vary. This analysis indicates that the side-feeding is significantly slower than the in-band cascade.

Isotopes of francium have been produced via a spallation reaction of thorium carbide and separated in the ISOCELE facility. The very weak beta branch (0.35%) of ²²⁰Fr decay and the beta decay of ²²²Fr leading to the levels of ²²⁰Ra and ²²²Ra, respectively, have been studied by means of gamma -ray singles and beta -gated gamma - gamma coincidence measurements. A strong evidence has been obtained for the 1^- state in ²²⁰Ra at 412.9 keV and 15 new levels have been added to the eight excited states known previously in ²²²Ra. The 3^- to 2⁺ E1 transition in the latter nucleus has been found to be remarkably enhanced compared with analogous transitions in the heavier radium isotopes. This enhancement together with the low energy of the 1^- state reflects octupole instability of ²²²Ra. The essentially higher energy of the 1^- state in ²²⁰Ra suggests that the latter nucleus already lies at the border of the octupole instability region. In contradiction to experimental indications the theory places ²²⁰Ra inside this region. For ²²²Ra it predicts a Q₁ value not far from the authors' experimental result but fails to reproduce Q₁, changes in ^224,226,228Ra nuclei.

The authors examine the alpha decays of heavy odd-mass nuclei, selecting those transitions which appear to proceed with the least hindrance due to nuclear structure incompatibilities between parent and daughter. They analyse the half-lives of 255 of these favoured transitions using a simple cluster model, and reproduce the absolute values of 216 of them to within a factor of 3. They achieve this level of agreement using exactly the same set of cluster model parameter values previously employed in an analysis of alpha decay of heavy even-even nuclei. In that analysis 125 out of a total of 154 half-lives were reproduced to within a factor of approximately 2. They conclude that this excellent overall fit provides strong evidence for the existence of preformed alpha particles in heavy nuclei, moving in orbits with large values of a global quantum number.

In their theory of alpha - gamma angular correlations, Rose and Brink (1967) leave the relative sign of different partial waves in alpha -capture undetermined. Some confusion has arisen in the experimental literature where the sign has been considered as somewhat arbitrary for alpha -decay. The authors derive an explicit relation between these two processes and show how the above sign may easily be fixed by considering the simpler problem of alpha -decay of a deformed nucleus polarized in a strong magnetic field. They discuss the anisotropy of the angular distribution for this latter problem.

Fusion/fission cross sections and T₂₀(fis) analysing powers together with angular distributions of quasi-elastic cross sections and T₂₀(qel) are reported for the interaction of an aligned ²³Na beam with a ¹³⁸Ba target at 143, 152, 164, and 174 MeV incident beam energies. The alignment dependent partial wave distributions for fusion, obtained from the analysis of the quasi-elastic data, were used as input for a statistical model calculation of the fission cross section and analysing power.

In order to obtain optical potentials for the elastic scattering of heavy ions from experimental cross sections a two-step procedure is chosen. First, a phase shift analysis of measured angular distributions is carried out. Then, the inverse scattering problem at fixed energy is solved within the modified Newton method. This two-step procedure has been applied to the elastic scattering of ¹²C on ¹²C at incident energies of E_CM=9.50 and 11.38 MeV. Optical potentials for the ¹²C+¹²C system are derived.

The authors report a new parametrization of fluctuations in the lateral distribution of gamma -ray initiated air showers based on three-dimensional Monte Carlo simulations. Such information, which has not been previously available, is necessary to calculate properly the effective areas of air shower arrays used as gamma -ray telescopes. They also consider the counting statistics of electrons recorded in detectors of sizes typically used in air shower arrays and find the distribution to be non-Poissonian. The appropriate distribution to use is discussed.

The general virial theorem is derived from the generalized Feynman-Hellmann theorem and then applied to discuss various relativistic wave equations.