Table of contents

A critical assessment of the dipole pomeron model with linear and curved trajectories is conducted. It is argued that the former version appears to be eliminated by the collider data. The latter version, however, could be regarded as a serious candidate for the description of the data after some modification.

A microscopic calculation of the interaction potential between two ¹²C ions within the framework of the alpha -particle model has been performed under the assumption that the ground state of each ¹²C nucleus is a linear chain of three alpha clusters. The potential obtained has been compared with the phenomenological one of Satpathy and Faessler and the agreement between the two potentials is found to be quite good in the tail region.

Yrast spectra and various moments of inertia are calculated for the nucleus ¹⁶⁸Hf and are compared with experimental data. Several theoretical methods yield a comparable agreement with experimental levels, but show a rather different behaviour of the pairing properties. The authors conclude that the knowledge of experimental level schemes alone does not yield information about an eventual pairing collapse.

Monte-Carlo simulations for pure U(1) gauge theory on a simplicial lattice are reported. The simplicial lattice formalism is reviewed briefly. Results are compared with other U(1) calculations and are found to be similar. The Wilson loops and the related string tensions for squares and triangles are examined. It appears that at beta approximately=0.85 a second-order phase transition occurs which deconfines electric charges in the weak-coupling region.

As a primitive model of spontaneous breakdown of chiral symmetry for strongly interacting quarks, the authors have considered confined fermions between parallel plates. The massless fermion field satisfies the chiral MIT boundary condition. Explicit expressions for the fermion condensate ( psi psi ) and the vacuum expectation value of the energy-momentum tensor are obtained.

The recently proposed effective profile expansion method for treating the Glauber-model S matrix has been applied to the case of inelastic nucleus-nucleus scattering at intermediate energies. Using target input information obtained from other experiments the authors analyse the 2⁺, 0⁺ and 3^- inelastic scattering of 0.698 GeV deuterons and 1.37 GeV alpha particles on ¹²C. It is found that, in general, consideration of the second-order term in the expansion brings theory closer to experiment. In particular, the 2⁺ and 0⁺ d-¹²C inelastic scatterings are reproduced fairly well.

Pion elastic scattering on ⁴He was calculated within the second-order optical model. The roles of pion double isospin and spin flip in intermediate states and of recoil correlation were investigated in some detail. A second-order term, which represents the effects of true pion absorption, is also included in the optical potential. A comparison was made between the results obtained using the Kerman-McManus-Thaler and Watson formulations of multiple scattering theory.

Bounds on the asymptotic D/S-state ratio of the deuteron established in an earlier paper are updated, with account of meson-exchange-current effects and new data. A method has been derived which determines whether or not the long-range part of a two-body potential model is consistent with measured deuteron properties, independent of the short-range behaviour. The outer part of the deuteron wavefunction is determined within narrow limits. Loose bounds on the pion-nucleon coupling constant are established.

The target-size and energy dependences of the effective two-body interaction range are obtained from the existing optical-model potentials for protons.

Cross sections for the excitation of nuclear giant resonances by positron annihilation in the atomic K shell are calculated. The positron and the electron are described by relativistic wavefunctions in the Hartree-Fock-Slater atomic potential. Nuclear transition densities and currents from self-consistent Hartree-Fock and RPA calculations with a Skyrme-type force are used. In the case of ²⁰⁸Pb, cross sections of the order of 10^-2 mb and 10^-4 mb are found for the excitation of E1 and E2 resonances, respectively.

The authors describe a method of extracting DWBA form factors for inelastic proton scattering from experimental cross sections. This method has been applied to ^58,60,62,64Ni(p,p') reactions at E=20.4 MeV, in this case for the O_gs⁺ to 2₁⁺ transitions. The results are compared with form factors obtained from microscopic calculations and (e,e') experiments. Some possible extensions of the method are proposed.

A quantum-mechanical model of coupled harmonic oscillators in collective coordinates of proton and neutron asymmetries is solved analytically, in a non-perturbative formalism, for the charge and neutron distributions in deep-inelastic reactions. The time evolution of the mean values (centroids) and the variances (widths) is studied for the initial distribution taken to be a two-dimensional Gaussian function. Model calculations are presented that show the detailed dependence of the relevant quantities on the variables of our model. Fits to the experimental data are made for the reactions ¹²⁹Xe on ¹¹⁶Sn and ¹²⁴Sn.

The ³⁹K(n, gamma )⁴⁰K reaction has been studied with thermal neutrons using curved-crystal, pair and Ge(Li) spectrometers. In total, 427 gamma rays have been observed and 302 were placed in a level scheme containing 62 levels below 5100 keV with energy errors mostly less than 100 eV. Nine levels were observed for the first time in the (n, gamma ) reaction. New information on spins and parities was deduced from the detailed gamma branchings. The neutron binding energy was determined to be 7799.55+or-0.08 keV. The level scheme is compared with shell and statistical-model predictions.

A new method for the determination of the K-shell fluorescence yield from the analysis of sum peaks observed with a high-resolution intrinsic Ge semiconductor detector in the decay of ⁷⁵Se is described. The value found is omega _K(As)=0.574(18), which is in agreement with the fitted value of Bambynek et al. (1977).

The relative gamma intensities of the 216, 248 and 464 keV transitions in the decay of ^84mRb were determined. The K-conversion coefficients of the 216 and 248 keV transitions were obtained as 0.74(4) and 0.033(3), respectively, using coincidence methods. These values of alpha _K are consistent with assigning the 248 keV transition as pure E2 and the 216 keV transition as M3+E4. From the relative gamma intensities of the 216-248 keV cascade, the total conversion coefficient of the 216 keV transition was evaluated as 0.93(6), assuming that alpha _T for the 248 keV transition was 0.038(3). The average adopted values of the M3 and E4 contributions to the 216 keV transition were obtained a 0.58(9) and 0.42(9), respectively. The transition probability for the 248 keV transition showed an E2 enhancement of 86(17) over the Weisskopf estimate. In addition, the reduced transition probability of this transition was found to be of the same order of magnitude as the 2⁺ to 0⁺ transitions in the neighbouring even-even nuclei, suggesting the possibility of core excitation in ⁸⁴Rb.

In an earlier paper the authors drew attention to accelerator experiments at laboratory energies of about 10¹² eV which indicated that the Feynman scaling model, which appeared to be successful at lower energies ( approximately=10¹⁰ eV), was breaking down to a significant degree. With new data now available from CERN pp experiments, which correspond to laboratory energies of about 2*10¹⁴ eV, it is possible to see whether or not the breakdown continues. They conclude that it does and indeed the discrepancy appears to be increasing. The significance of the results for the interpretation of cosmic-ray data is examined.