Table of contents

Using the pion-cloud model of nucleons, the author finds that the observed ratio mu (p)/ mu (n) can be explained in the presence of core contributions to the nucleon moments.

It is shown that the only Regge eikonal model which succeeds in describing the ISR data over a wide-t range fails at collider energies.

The analysing power A_y0 of elastic proton-proton scattering has been measured at 582 MeV for 14 angles from the 20 to 80 degrees CM.

A new six-parameter representation for the elastic non-unitary 2*2 nucleon-nucleon scattering matrix above the inelastic threshold is presented. This representation has a simpler form than those suggested recently by Klarsfeld (1983) and by Bryan (1981).

The strength distribution of the two-quasiparticle states which could be excited in two-neutron transfer reactions on Sn isotopes are calculated within the quasiparticle-phonon model. It is shown that the substructures observed via the ( alpha ,⁶He) reaction on ¹¹⁶Sn by Gerlic et al. (1982) can be observed in other Sn isotopes.

The approximation to a folding potential by means of a Taylor expansion of the Woods-Saxon (or similar) potential up to an order as high as eight is likely to be far from reasonable unless the range of densities is small not only compared with the distance where the folding is computed but also with the diffuseness of the potential: the latter condition is hardly fulfilled at the relevant distances in an optical potential for heavy ions.

A pair of exact, complex conjugate solutions is obtained for SU(2) Yang-Mills-Higgs theory in the Prasad-Sommerfield limit. The Euclidean actions corresponding to these solutions are found to be finite and complex. These flat-space solutions are transformed to the de Sitter space by a standard procedure.

Recently it was shown that the nuclear stability against pion condensation can be caused by interference between pseudovector and pseudoscalar pi N interactions. The authors determined the value of the mixing parameter x from the transition energies between pi -mesoatomic states in nuclei from ¹²C to ²⁰⁹Bi as x=-0.32+or-0.01. For such values of x the nuclear matter is close to pion condensation at densities 0.25n₀<or=n<or=0.5n₀ where n₀ is the ground-state density.

Estimates of the bombarding energies necessary to reach the quark-gluon phase in heavy-ion collisions are presented within a hydrodynamical framework. At intermediate energies (3-7 GeV/nucleon) the quark-gluon matter formed is predicted to be rather cool (below 100 MeV), i.e. much colder than nuclear matter without phase transitions. Further, the consequences of first-order phase transitions from the neutron matter to pion-condensed matter and quark matter are discussed for neutron stars. Quark matter does not fulfil the conditions for the existence of a third stable branch, e.g. stars with quark cores. Because of observational constraints on neutron-star masses, pion condensation is restricted to a narrow first-order phase transition at best. Due to this restriction the rapid growth of a pion-condensed core in a neutron star cannot appear as a supernova-like event as suggested in earlier work.

The recent work of McTavish (1982) on the momentum and energy dependence of non-local separable potentials is improved to ensure that the equivalent potentials are not singular. The improvement provides a basis for a phase equation. This phase equation is a first-order nonlinear ordinary differential equation similar to that for local potentials. It is a great simplification on the integro-differential equation obtained by Calogero (1967).

The excitation energies, spins, parities, total widths and neutron elastic scattering widths of seven T=¹/₂ levels of ¹³C at excitation energies between 11.5 and 12.5 MeV have been determined via a phase-shift analysis of n+¹²C total cross section, elastic differential cross section and analysing power data in the energy range from 7.03 to 8.56 MeV. The proposed level structure for ¹³C is consistent with the known structure of the mirror nucleus ¹³N. Above 12 MeV excitation energy, the results of the phase-shift analysis disagree significantly with the R-matrix analysis of n-¹²C cross section data recently reported by Knox and Lane (1982).

Using a gamma -ray spectrometer consisting of a liquid deuterium target and a photoneutron time-of-flight detector, the total absorption cross section of ¹⁶O was measured in the energy range from the 3 to 38 MeV. The total photonuclear component of the cross section integrated from 10 to 30 MeV was found to be (182+or-16) MeV mb, or (0.76+or-0.07) TRK sum-rule units. This result is compared with previous measurements, and its significance to the theory of meson-exchange currents is discussed.

A high-resolution study of proton inelastic decay from ⁵/₂⁺ resonances in ⁵¹Mn has been performed in the energy range E_p=3.26-4.28 MeV. Magnitudes and relative signs were determined for three decay channels for 38 ⁵/₂⁺ resonances in ⁵¹Mn. Very large amplitude and width correlations were observed.

Neutron activation cross sections for Ti isotopes at 14.8 MeV were measured using Ge(Li) gamma -ray spectroscopy. The linear least-squares method was used to resolve the interfering reactions of neighbouring isotopes. The results obtained are discussed in detail and are compared with pre-equilibrium, equilibrium and semi-empirical calculations.

The cross sections for the reactions ¹¹³In(n,2n) and (n,n') and ¹¹⁵In(n,n'), (n,p) and (n, alpha ) at 14 MeV, and ¹¹⁵In(n,2n) from 14 to 18 MeV were measured by the activation technique. Special emphasis was placed on the accuracy of the results, and so full experimental details are included. The correlations between the measurements are considered, these being especially important for ^112m,gIn. Isomeric cross section ratios were measured at 14.3 MeV: sigma _m/ sigma _g=(4.32+or-0.20) for ¹¹³In(n,2n)^112m,gIn and sigma _m/ sigma _g=(4.59+or-0.03) for ¹¹⁵In(n,2n)^114m,gIn. The results were compared with other published values, which show a very wide spread so that these cross sections cannot be considered well known at the present time. During the course of this work half-lives were measured for ^112gIn((14.97+or-0.10)min), ^112mIn((20.56+or-0.06)min) and ¹¹⁴In((71.6+or-0.1)s). The decay scheme of ^114mIn was investigated, and gamma -ray intensities and a total internal conversion coefficient of (5.101+or-0.061) for the 190 keV gamma ray were obtained. In the case of ^112mIn arguments are presented to support the theoretical total internal conversion coefficient for the 156 keV gamma ray of 6.80.

The K-electron-capture probabilities to the 437 and 384 keV levels in the decay of ¹³³Ba have been determined from a measurement of gamma-ray intensities in conjunction with an analysis of the K X-ray-gamma-ray sum peaks. The results are independent of fluorescence yield and detector efficiency.

The lateral distribution of densities recorded by thin scintillators in air showers produced by primary cosmic rays with 5*10¹⁸<E<5*10¹⁹ eV has been measured at the Haverah Park air-shower array. For distances 70<r<1200 m and zenith angles <30 degrees the authors find excellent agreement with results from the Yakutsk and Volcano Ranch. The measurements are used to bolster previous claims for the existence of primary cosmic rays with energies >or approximately=4*10¹⁹ eV. Maps of the density patterns recorded in two events are shown.

The absolute intensity of muons moving in the near-vertical direction has been measured under 209, 504, 1025, 1547 and 2066 g cm^-2 thicknesses of absorber. In these measurements a range spectrograph was employed and this consisted of four arrays of crossed neon flash tube detectors triggered by a fourfold or a sixfold Geiger counter coincidence. The use of flash tubes to delineate the trajectory allowed unambiguous identification of single-particle traversals and improved the accuracy of determination of the acceptance solid angle. Since the nature and thickness of each of the absorbers were known, the different thicknesses were converted to muon energies and used to define the shape of the sea-level integral muon momentum spectrum, over the range 0.4 to 3 GeV/c. The diffusion model for particle propagation through the Earth's atmosphere is used to derive the muon spectrum and a comparison with the experimental data gave a value of -2.68 for the exponent of the pion production spectrum. An empirical relationship was derived to express the depth-intensity variation which best represents the present data together with that reported by other workers over a range of depths from the 10 to 10⁴ hg cm^-2 of standard rock measured from the top of the Earth's atmosphere. This relationship, together with the best-fit muon integral spectrum was used to produce a range-energy curve for muons in standard rock.