Table of contents

Using a simple model for the breaking of SU(6) symmetry in the MIT bag model the authors show that the observed x behaviour of deep inelastic structure functions is consistent with the negative sign of the neutron charge radius.

Hartree-Fock calculations carried out with the Skyrme interaction for closed-shell polyneutron systems up to ¹⁸⁴n show that bound states are not possible unless the attractive component of the interaction is substantially enhanced.

The escape width ( Gamma _d spin up), damping width ( Gamma _d spin down) and the average interaction potential (V_d) between a nucleon in a doorway state and a nucleon in more complicated states of the nucleus are discussed as a function of 2 pi ( Gamma _mu )/D. It is found that the probability with which a doorway state is present in a compound state is equal to (n_d/n)² and that (V_d) resembles closely a simple harmonic-oscillator potential. The magnitude of the potential is approximately 8 keV.

From the level structure of ¹³⁹Nd obtained by the ¹²⁸Te(¹⁶O,5n) reaction, one deduces that a shape change from prolate to oblate occurs between the N=77 and N=79 neodymium isotopes.

For elastic scattering of polarised tritons, optical-model parameters with V_so approximately 2 MeV give as good fits to analysing-power data as do potentials with V_so approximately 6 Mev.

In the reaction ¹⁴N(³He,p)¹⁶O at 15 MeV bombarding energy, the observed excitation energies, L values and cross sections for ¹⁶O levels at 14927+or-2 and 15785+or-5 keV establish them as 2p-2h states with T_p=T_h=0, and strongly suggest J^pi =1⁺ and 3⁺ respectively.

The distribution of the single-particle strength in ¹²¹I has been investigated by the reaction ¹²⁰Te(³He,d) using a Q3D magnetic spectrograph and is interpreted within the framework of the three-particle-cluster-vibrational-core coupling model.

The full width at half maximum of atmospheric Cerenkov pulses from extensive air showers has been measured with a wide-band recording system for EAS with sizes of about 5*10⁵ particles in the core distance range 0-250 m. The observed pulse widths are appreciably less than those reported by other groups with showers of greater size, implying that the full width at half maximum is sensitive to shower development.

A class of radiative decays of psi particles is studied in the vector-meson dominance model to determine the behaviour of the off-shell vector-meson-photon coupling constants. It is found that these are suppressed by about a couple of orders of magnitude compared with their on-shell values and the suppression thus obtained may be much larger than is usually believed. Different approaches for the incorporation of the suppression in simple VDM are discussed, and the necessity of considering suppression due to off-shell effects at both the hadronic and photonic vertices is emphasised. While the authors' model is constructed in the constructive interference scheme, the parallel arguments in the cancellation hypothesis are closely examined in an appendix to the paper; it is found that in this hypothesis also off-shell suppression factors are necessary to give currently acceptable numbers, and some of the problems associated with this approach are indicated.

By utilising a dispersion-theoretic calculation of the isospin-zero helicity non-flip amplitude to supplement the experimental data, and by making physically reasonable assumptions about isospin-one dominance of certain helicity flip amplitudes, the authors have been able to obtain a unique, stable set of amplitudes in the region -0.7<or=t<or=-0.1 (GeV/c)² at p_L=6 GeV/c. They demonstrate how the qualitative structure of the amplitudes is determined by the data, and use their amplitudes to predict the values of observables not yet measured.

The parameters D, R, R' and P for pp elastic scattering have been measured in the centre-of-mass angular range 13 degrees to 58 degrees with an accuracy of about +or-0.02 at 209, 324, 379, 425 and 515 MeV. These results are incorporated with earlier data into a phase-shift analysis. Phase-shifts are generally in agreement with the theoretical predictions of the Paris group, although the F-wave spin-orbit combination is rather stronger than predicted. The fitted value for the pi ⁰pp coupling constant in g₀²=14.06+or-0.65.

The absolute normalisation of the polarisation in pp elastic scattering at 24 degrees lab has been determined by means of a double-scattering experiment to an accuracy of +or-1.5% at five energies between 200 and 520 MeV.

A study is made, within the Delta -configuration approach, of several processes which could contribute to the imaginary components of nucleon-nucleon phase-shifts. However, as in earlier estimates with this model, the final results for low partial waves are far from the values suggested by phase-shift analyses. The imaginary components in high partial waves are calculated in the Born approximation and could be utilised in removing some of the ambiguities in phase-shift analyses at energies less than than 1 GeV. In addition, a new transition potential for generating Delta configurations is derived in such a way as to be more consistent with the two-pion exchange contribution of recent semi-theoretical nucleon-nucleon potentials.

A complete classification and a method of construction of the wavefunctions of the octupole oscillator, according to the physical group chain U(7) contains/implies R(7) contains/implies R(3), are given. The method is based on the concepts of elementary factors (elementary permissible diagrams) for the reduction process in the chain U(7) contains/implies R(3) and of traceless operators for the extraction of irreducible representations of R(7) from those of U(7). The seven quantum numbers used for labelling the wavefunctions are the number of phonons, the seniority, the spin and its projection, the numbers of quartets and sextets of phonons coupled to spin zero, and a label for a 'residual coupling'. A connection between the present problem and the theory of covariants of algebraic forms is mentioned. The construction of the oscillator basis is a first step towards a description of the octupole motions, in their full variety, in nuclei.

A detailed investigation of the gamma decay of four analogue resonances in the reaction ⁵¹V(p, gamma )⁵²Cr has been performed in the proton energy range E_p=0.7-2.0 MeV. From (p, gamma ) angular distributions, mixing ratios of primary gamma transitions depopulating the analogue resonances and J^pi values of some states populated in the gamma decay have been obtained. Decay schemes, branching ratios, partial gamma widths and resonance strengths have been determined for these IARs. Upper limits of M1 transition rates from analogue states to low-lying states are found to be of the order of few mWu. The analogue states are seen to decay significantly to a group of states in the region of excitation 3.4 to 6.0 MeV.

Resonances consistent with fragmented g_9/2 analogue resonance have been found in ⁵⁷Co corresponding to the E_x=2.454 MeV level in the ⁵⁷Fe parent nucleus. The resonance was located through the ⁵⁶Fe(p, gamma )⁵⁷Co reaction. Total gamma -ray spectra were measured with a Ge(Li) detector in 2 keV steps in the expected proton energy range. Excitation functions for the different primary gamma transitions were constructed. The g_9/2 IAR were found in two components at E_p=3728 and 3735 keV. The angular distributions of gamma rays were measured at these two bombarding proton energies. The two resonances were suggested to have spin and parity J^pi =⁹/₂⁺ based on the gamma -ray excitation functions and angular distribution measurements. The gamma -branchings and absolute transition probabilities were also determined. The Ml gamma transitions from the g_9/2 IAR components going to the possible anti-analogue level at E_x=4.585 MeV excitation energy have absolute transition strengths of 1.8*10^-2 Wu and 1.2*10^-2 Wu.

The reactions ⁶¹Ni( alpha ,n gamma )⁶⁴Zn and ⁵⁶Fe(¹¹B,2pn gamma )⁶⁴Zn have been used to make spin assignments of J^pi =6⁺,6⁺ and 7^- to the levels in ⁶⁴Zn at 3994, 4237 and 4636 keV respectively. Lifetime measurements of 175+or-50 fs and 190+or-60 fs for the two J^pi =6⁺ levels yield E2 transition strengths of 23+or-5 Wu for the 6₁⁺ to 4₁⁺ transition and 37_-9⁺¹⁷ Wu for the 6₂⁺ to 4₂⁺ transition. These results indicate the presence of two quasi-bands in ⁶⁴Zn.

A measurement of the total neutron cross section of ⁸⁹Y from 0.3 MeV to 9.0 MeV is presented. Values for the nuclear level density and average neutron total width of the levels in ⁹⁰Y are deduced for excitation energies of 7.26, 7.86 and 9.61 MeV. The measurement is compared with the theoretical cross section derived from the generalised optical potential of Wilmore and Hodgson (1964) and also with an R-matrix calculation of Ramavataram et al. (1975). Fluctuations are observed in the cross section below 1.5 MeV. An analysis of the fluctuations indicates they can be explained by fluctuations in the widths and spacings of the levels in ⁹⁰Y.

The nuclei ¹²⁹Xe and ¹³¹Xe have been studied by Coulomb excitation and by ( alpha ,n) reactions on ¹²⁶Te and ¹²⁸Te. The authors report eleven new levels for ¹²⁹Xe and six for ¹³¹Xe and B(E2) spin up values for some of the low-lying states. The present Coulomb excitation experiments together with published beta -decay work enable some spin-parity assignments and restrictions to be made. The data are broadly consistent with the predictions of the particle-vibrator coupling model, although a thorough comparison requires further spectroscopic measurements and more detailed theoretical calculation.

A detailed analysis of all the available experimental data concerning the h_11/2 system of levels in ^189,193,195Au is made with the generalised particle-asymmetric rotor model applied previously to the description of the positive-parity states. The influence of several Nilsson orbitals on such h_11/2 systems is also investigated in detail.

The energy spectrum of unaccompanied hadrons has been measured at a depth of 730 g cm^-2 in the atmosphere. The energy was determined by a deep calorimeter (960 g cm^-2) of area 4 m². For charged hadrons unaccompanied in a 3.3 m² spark chamber placed above the calorimeter, the observed flux was fitted in the energy range 100<E<10000 GeV.

The average lateral density distribution of muons in EAS initiated by cosmic-ray primaries of energy 10¹⁷ eV has been established. EAS whose measured muon content differs from that expected for an average shower are selected, i.e. muon-'poor' and muon-'rich' showers are isolated. An harmonic analysis in right ascension is performed on these different classes of muon-selected EAS. For muon-'rich' showers a certain consistency of phase in the first harmonic shows up at approximately 12 h right ascension. However, none of the derived first-harmonic amplitudes are significant statistically.