Table of contents

The authors investigate the proximity scaling for the nuclear part of the nucleus-nucleus potential derived from the collision of two infinite nuclear matters flowing through each other. It is found that the proximity theorem is satisfied to a good extent at each value of the projectile energy per nucleon. They simplify the interaction potential between different pairs of nuclei by the product of a geometrical factor, dependent on the radii of the interacting nuclei, and a gaussian distribution whose parameters depend on the projectile energy per nucleon.

The resonance-like structure observed in the alpha -cluster transfer process of collisions between the alpha particle s-d shell nuclei and its suppression on adding neutrons to the target or the projectile (or both) are shown to be given as a collective mass transfer in the dynamical fragmentation theory.

Effective boson numbers are introduced in IBA-1 calculations to simulate the partial subshell closure effects at Z=64. The energy levels, wavefunctions and B(E2) values of Sm isotopes are calculated and compared with the experimental data. It is found that the agreement with the experimental data can be improved by introducing effective boson numbers in the calculations.

The authors present new results on the energy scaling behaviour of the lateral distribution of Cerenkov radiation in photon-induced air showers. It is shown that the lateral distribution of Cerenkov radiation scales with energy provided that the showers are observed at the same stage of development. They also show that earlier calculations on the lateral distribution of Cerenkov radiation in air showers are in favour of their results.

It is suggested that an algebra formed of the hypercomplex number systems (division algebras) is in large measure responsible for the symmetries to which the elementary particles are subject, the multiplets into which they fall and even the geometry in which they exist. In this new approach to applying hypercomplex number systems the standard symmetry is derived as a subgroup of an SO(32) symmetry of a hypercomplex inner product.

Many-body quantum techniques are used to investigate the restoration of chiral symmetry in a model with a chiral invariant effective Lagrangian and where a dynamic breaking of chiral symmetry occurs at the quark level. The effects of the restoration of chiral symmetry on collective qq modes are studied. It is shown that, in addition to a vibrational spectrum, the model has a rotational spectrum corresponding to states with good chirality. The lowest excited state of the rotational band has pion quantum numbers and a finite energy of quantal origin.

The authors consider the non-relativistic approach to the Gamma and xi families by solving the Schrodinger equation through the variational method. A truncated basis of harmonic-oscillator wavefunctions is used as the trial function. They study two kinds of phenomenological potentials for the qq interaction and fit the parameters by analysing the 1 ³S₁ and 2 ³S₁ states. They also calculate hadronic, leptonic and electric dipole transition widths for these bb and tt systems.

The authors discuss the problem of obtaining values of a function f(x) (where 0<x<1 is typically the longitudinal momentum fraction in high-energy calculations), given that a finite number of moments ( integral f(x)xⁿdx=f(n)) are known. They show that the simplest possible method, expansion in Legendre polynomials of argument (2 x-1), gives good values for f(x) when only eight moments are known. This gives better results for this situation than the methods of Lin (1984) and Yndurain (1978), provided the input moments are accurate to one part in 10⁵ or better.

The authors use Feynman diagrams to calculate the contributions of the pion exchange current to the pi D to pi D scattering in the region where the Delta ₃₃ resonance is dominant. The results show that the contributions to the differential cross section, although small, are comparable with that of the double scattering.

Pion elastic scattering by ⁶Li in the region of the Delta ₃₃ resonance is investigated on the basis of an alpha -n-p cluster model of ⁶Li. Experimental pion-alpha and pion-nucleon scattering amplitudes are used as input as well as realistic three-body alpha -n-p wavefunctions. Multiple scattering contributions are calculated within the eikonal framework. The results of the calculations agree reasonably well with differential and total cross section measurements in the pion energy range from 100-300 MeV. Vector polarisation iT₁₁ is predicted to have strong oscillations of diffractive origin. Inelastic scattering to the O⁺, T=1,3.56 MeV state in ⁶Li is not so well reproduced by this model.

Assuming constant nuclear density and taking into account the degree of freedom at the neck in the nuclear and Coulomb energy calculations, the author carries out as study of experimental heavy-ion fusion data for asymmetric systems. The calculated barrier heights and positions are in good agreement with experimental data. Using a dynamic model depending on only one parameter (adjusted once and for all) he investigates the problem of the fusion cross-section saturation for light and medium nuclei. The increase of the fusion cross section with the incident energy of the projectile is limited at high energies by a strong dissipation occurring around the contact point. In the high angular-momenta range the top of the l-wave barriers correspond to shapes very similar to two touching spheres and dynamic and proximity effects are particularly important. The dissipation model within the relaxed-density potential allows one to satisfactorily reproduce the slope and curvature of the fusion cross sections in the whole mass range.

beta decay in the presence of an external electromagnetic field is investigated, taking into account the non-zero neutrino rest mass. The spectrum of electrons and polarisation effects of different orientations of nuclear spin are considered. It is shown that the electromagnetic wave substantially modifies the boundaries of the spectrum of beta electrons. The results, which include an analysis of the total decay probability in intense magnetic fields, may have various astrophysical implications.

The deep proton-hole states 1g_9/2 and 1f_5/2 are found to be fragmented through the coupling of these states with the low-lying 2⁺, 3^-, 5^-, 4⁺ and 6⁺ collective states as well as with the high-lying 2⁺' and 1^-' collective states arising from the giant resonances in ²⁰⁸Pb. The excited 1g_9/2 and 1f_5/2 inner-hole states detected through the most recent ²⁰⁸Pb(d,³He) reaction can be quantitatively explained in terms of the core-polarisation effect on these two hole states.

The charge to neutral ratio for hadrons in EAS has been calculated within a scale breaking dynamical model of multiparticle production at high energy. It has been shown that the C/n ratio decreases slowly with increasing hadron energy. It implies that the existence of heavy primaries is not required to explain the characteristics of EAS if the scale-breaking model, with <n> approximately S¹3/(S in GeV²), is applied to the multiparticle production aspects of high-energy EAS.

The full set of data obtained by the Sydney University giant airshower recorder (SUGAR) has been reanalysed to take into account the effects of afterpulsing in the photomultiplier tubes. Event data have been used to produce a spectrum of 'equivalent vertical-muon number' and from this, two model-dependent primary-energy spectra are obtained. All three spectra show good evidence for the 'ankle': a flattening at 10¹⁹ eV. There is no sign of the cut-off which would be expected from the effects of the universal black-body radiation.

The full set of data obtained by the Sydney University giant airshower recorder (SUGAR) has been reanalysed to take into account the effects of afterpulsing in the photomultiplier tubes. The authors examine the distributions of shower-arrival directions for evidence of anisotropy and conclude that the data is consistent with isotropy of arrival directions.