Table of contents

A nuclear parity-violating isovector potential ( Delta I=1) is calculated for the Weinberg-Salam model including QCD corrections with flavour symmetry breaking. Two pieces of the isovector potential can interfere in such a way as to explain the small intensity of Delta I=1 nuclear parity-violating potentials in some transitions.

The effects of the spin and flavour of quarks on terms contributing to the bubble sea are considered, and are shown to lead to the difference between the u and d distributions being negative, as required by experiment. The antiquark asymmetries are estimated, and are found to be very different from those arising from the gluon sea. In principle, this gives a way of separating these contributions to the sea.

Elastic pd and p(NN) to Nd scattering at backward angles have been studied within the one-pion-exchange model. The p(NN) to Nd amplitudes depend on the spall-distance behaviour of the (NN) relative wavefunctions only. A(p,Nd)B quasifree scattering is described in terms of the p(NN) to Nd amplitudes.

The Coulomb distortion of nuclear transitions induced by incident pion beams is investigated in the eikonal model. Taking a phenomenological ansatz for the transition amplitude, defined in terms of that for the elastic, the pi ⁺, pi ^- difference is predicted to be much smaller than for elastic scattering. This is in agreement with measurements on the first 2⁺ excitation in ¹²C in the resonance region.

The magnetic susceptibility of neutron matter, interacting through the Reid (1968) soft-core potential, is calculated within the framework of the lowest-order constrained variational technique of Owen, Bishop and Irvine (1977). The magnetic susceptibility predicted by the LOCV calculation is considerably larger than that obtained in Brueckner calculations by Haensel. It is further increased when the N*(1234) degree of freedom is allowed for explicitly. Despite these increases in susceptibility there is no evidence for a ferromagnetic phase transition.

Measurements of the full width at half maximum of atmospheric Cerenkov radiation from extensive air showers have been used to study the dependence of this parameter on sea-level shower parameters. Using two simple models of shower development, relationships between the height of the shower maximum from the observer and the pulse width have been derived and, assuming a particular theoretical relationship between height and pulse width, the dependence of depth of shower maximum on size. It appears that showers with sea-level sizes around 10⁶ develop rather early and it is suggested that the depth of maximum may increase rapidly with shower size in this shower-size range.

For pt.I see Phys. Lett. vol.67B, no.3, p.327 (1977). Unitarity bounds on the shape of the diffraction peak obtained using only the positivity of the absorptive part of the partial waves are extended to include the boundedness restriction and are compared with data. A detailed explanation is given for a curious phenomenon that has recently been observed to arise in variational problems of this kind.

Expressing the non-leptonic decay amplitudes of ¹/₂⁺ and ³/₂⁺ baryons in terms of the eigenamplitudes in different channels and assuming intermediate states to be non-exotic. The authors are led to the hypothesis of octet dominance. Assuming the weak Hamiltonian to be symmetric under the s and u channels, they further obtain Sigma ₊⁺=0 in s wave and the Lee-Sugawara sum rule in p wave in the SU(3) framework. These assumptions also yield a few extra relations which compare favourably with experiment.

Possible effects of resonance production on the meson inclusive distribution in the fragmentation region are investigated in the framework of the parton recombination model. From a detailed study of the data on vector-meson production, a reliable ratio of the vector-to-pseudoscalar rates is determined. The authors examine the influence of the decay of the vector mesons on the pseudoscalar spectrum and find the effect to be no more than 25% for x>0.5. The normalisation of the nonstrange antiquark distributions are still higher than those in a quiescent proton.

By solving the Hilbert-Smidt problem for the Faddeev equation for the N Delta ₃₃ system it is shown that, under the condition where pi , rho and omega mesons exchange between N and Delta ₃₃ in the system N Delta ₃₃, bound and resonance states are absent.

The charge-asymmetric term E_a(N-Z) in the volume part of the nuclear binding energy of heavy nuclei is estimated using Brueckner theory and the variational approach. Calculations are performed using phenomenological charge-symmetry-breaking nuclear interactions, which are consistent with Coulomb displacement energies in mirror nuclei. The results obtained using standard Bruckner theory are very close to those obtained in the variational approach with realistic state-dependent correlation functions. An estimate E_a approximately=-0.6 MeV is obtained, in good agreement with semi-empirical estimates of this quantity.

Relations for energy per particle, effective mass and magnetic susceptibility in neutron matter are derived using a simple three-parameter density-dependent effective interaction constructed in an earlier work (see ibid., vol.5, no.1, p.85 (1979). The effective mass M*/M, which has a value 0.985 at k_n=0.5 fm^-1, decreases steadily with increase in density. The ratio chi _F/ chi of the magnetic susceptibility of a Fermi gas of non-interacting neutrons to that of neutron matter increases with density up to k_n=1.4 fm^-1 and then decreases. The results of Haensel (1975) calculated with the Mongan nonlocal separable potential show a similar trend where chi _F/ chi decreases beyond k_np2.4 fm^-1. As chi _F/ chi is quite sensitive to the odd-state interaction energy, which is usually negligible up to a density corresponding to k_n=2 fm^-1, the results of magnetic susceptibility obtained with the simple effective interaction mentioned above acting in even states only are expected to be reliable only below this region of density.

An extension of the folded Yukawa potential, surface and Coulomb energies formulae for the fusion of heavy ions (or fission fragments) with different charge-to-mass ratio is presented. One also has to add the volume contribution to the deformation energy. For various combinations of nuclei along the Green approximation of the line of beta stability, the general trends in the variation of interaction barriers, fusion Q values and fission barriers are studied, showing that errors of the order of some tens of MeV could appear if the difference between charge densities is ignored. Calculated interaction barriers are in good agreement with available experimental data for some 58 pairs of colliding nuclei. PES for the reactions ¹⁰⁹Ag+⁴⁰Ar, ⁸⁴Kr+⁶⁵Cu, ⁷⁵As+⁷⁴Ge, ¹³⁸Ce+⁵⁷Fe, ¹⁴⁴Nd+⁶¹Ni, ¹¹⁶Cd+⁸⁴Kr and ¹⁴²Nd+⁸⁴Kr are computed using the parametrisation of the asymmetric spheroid with neck. The relative values of the saddle-point energies for a real system and for a charge-equilibrated one show how important this effect could be in the entrance channel of a fusion reaction.

The double differential inelastic scattering cross sections of 14.8 MeV neutrons by deuterons have been measured using the time-of-flight technique and a NE 230 scintillator as a scatterer. The total neutron emission cross section in a forward hemisphere has been determined as 240+or-30 mb. The present measurements have been compared with previous measurements on neutron and proton emission. The differential cross sections for the excitation of the 9.63 MeV state in ¹²C decaying through emission of charged particles have been measured to be 5.3+0.5, 5.6+or-0.6 and 6.2+or-0.6 at 78 degrees , 89 degrees and 99 degrees in the centre-of-mass (CM) system.

The reaction ⁴⁰Ar( alpha ,n gamma )⁴³Ca was used to populate the levels in ⁴³Ca at bombarding energies between 5.5 and 19 MeV, gamma - gamma coincidence measurements at E_alpha =8.5, 15 and 16 MeV being used to establish the decay scheme of 53 levels. Several new levels and new decays of levels with high angular momentum were established. The Doppler-shift attenuation method was used with solid Ar targets to deduce the mean lifetimes for most of these levels. A Ge(Li)-Na(Tl) escape-suppressed spectrometer and a three-Ge(Li) Compton polarimeter were used to measure the angular distribution and linear polarisation of gamma rays at alpha bombarding energies of 7.0, 14.5 and 17 MeV.

The Fermi matrix element M_F for the beta decay of the ground state of ⁶⁶Ga to the ground state of ⁶⁶Zn is calculated using the effective one-body spheroidal Coulomb potential with Nilsson wavefunctions. It is shown that the theoretical estimates of M_F are sensitive to the deformation parameter. By comparing with the experimental value of M_F, it is found that the deformation parameter beta of ⁶⁵Ga is between 0.2 and 0.3.

The positive-parity states of ⁸⁵Kr are calculated by coupling the single-neutron motion to the quadrupole vibrations of the ⁸⁴Kr core. The energy levels and spectroscopic factors are in reasonable agreement with recent (d,p) data.

The directional correlations of gamma transitions in ¹⁰⁵Rh have been measured from the beta ^- decay of 4.4 h ¹⁰⁵Ru utilising a Ge(Li)-Na(Tl) spectrometer. The present results, which include measurements on six gamma cascades not studied previously, when combined with other available data establish spin and parity assignments for the majority of low-lying levels in ¹⁰⁵Rh up to about 1 MeV. The multipole mixing ratios delta (E2/M1) calculated from the measured angular correlations are presented.