Table of contents

The authors show that the measurement of only eight real parameters consisting of the differential cross section y₀, the analysing power T₂₀ and the polarisation transfer observables C_x,x, C_x,y, C_y,y, C_x,xz, C_x,yz and C_y,xz are sufficient for the complete determination of pi -d elastic scattering amplitudes in the transverse frame.

New results are given to two-loop order and for quark masses of arbitrary flavour for the perturbative contribution to the coefficient function of the unit operator in the operator product expansion (OPE) of a vector correlator. A simple transformation of the presented results provides results for axial correlators.

The authors study a generalised Schwinger model, with different left and right couplings, in the massive fermion case. Using the path-integral approach to the bosonisation they establish its equivalence to a certain generalised sine-Gordon model. This allows them to obtain necessary conditions to be fulfilled by the parameters of the model in order to have a consistent theory.

The authors propose an ultra short range attraction in the nucleon-nucleon potential to imitate some qualitative features of the quark model. A modified version of the Reid soft core potential is presented. It is proved to be capable of describing the physical observables of the deuteron as well as the original Reid soft core potential. The probability of the six-quark configuration of the two-nucleon system can be defined and a good estimate for this probability can be obtained.

The extraction of the gamma N Delta transverse and longitudinal quadrupole transition form factors g_E and g_C from the interference measured in (ep, e'p' pi ⁰) at resonance is discussed. It is shown that the background mechanisms in the non-resonant channels are substantially depressed thus allowing the direct determination of g_C and g_E. The two quantities, which have to be equal at pseudo-threshold, vary for 0>k²>-0.6 (GeV/c)² between 0 and -0.1 g_M. The necessity of an explicit evaluation of dispersive effects coming from pionic contributions to confirm their four-momentum transfer dependence and their connection with the pseudo-threshold value is stressed.

The staggering phenomenon is studied in the framework of the proton-neutron interacting boson model. It is found that the quadrupole interaction between like bosons plays an important role in the description of this phenomenon. When this interaction is strong, the spectrum shows less staggering and vice versa. The staggering phenomena in the Ru isotopes and the ¹⁹⁶Pt are studied.

The authors show that for deep inelastic lepton-nucleus scattering, the conditions which validate the impulse approximation are hardly satisfied when using ordinary instant form dynamics in the rest frame of the nucleus, whereas they are well satisfied when using instant form dynamics in the infinite-momentum frame, or using light-front form dynamics in an ordinary frame. Therefore a reliable theoretical treatment of deep inelastic lepton-nucleus scattering should be performed in the time-ordered perturbation theory in the infinite-momentum frame, or its equivalent, the light-cone perturbation theory in an ordinary frame. To this end, the authors extend the light-cone quantum field theory to the baryon-meson field to establish a relativistic composite model of nuclei. They then apply the impulse approximation to deep inelastic lepton-nucleus scattering in this model. As a first approximation, they consider only the nucleon degrees of freedom and neglect the Z-graph contributions. It is found that the results seem able to explain the EMC effect in trend but overestimate the ratio of the differential cross section for a bound nucleon to that for a free nucleon by about 8%. Some comparisons of the model with several relevant models are also presented.

An analytical formalism for heavy-ion-induced elastic and inelastic scattering is developed within the framework of direct reaction theories. This formalism is based on a generalised semiclassical method which has been shown to be in excellent quantitative agreement with a fully quantum mechanical approach over a wide range of Q-values. Analytical expressions for the elastic phase shift, the inelastic amplitudes due to the Coulomb and nuclear excitation are derived and the magnetic substate dependence is explicitly shown. In particular, the Coulomb inelastic amplitude is found to be exact provided the heavy ions do not overlap. It is shown that the analytical formalism developed in this paper is in excellent agreement with the numerical calculations.

A semiclassical technique is developed for calculating the angular and energy distributions of charged particles evaporated from deformed nuclei. It includes an analytical expression for particle momentum at infinity via its momentum at the emission point, which reasonably reproduces exact calculations, and a triangular weighting function for averaging over the cascade temperature. Essential reduction in computational effort is achieved due to a compact expression for emission widths and a phenomenological treatment of penetration through an aspherical barrier. The application of this technique to alpha -emission from strongly excited Yb isotopes with aligned spin has produced values of the deformation parameter which are in good agreement with liquid drop model calculations.