Table of contents

The T₂₀ analysing power has been measured at 0 degrees for the ¹H(⁷Li,d)⁶Li reaction leading to the ground and first excited states in ⁶Li. The data have been analysed in terms of a simple cluster model of ⁷Li. The T₂₀ value for the ground-state transition is well described assuming a ⁶Li+n cluster structure for ⁷Li where the ⁶Li core acts as a spectator and no nucleon spin flip takes place.

The production of intermediate-mass Higgs bosons in strong electromagnetic fields prevailing in ultrarelativistic heavy-ion collisions is studied. To exclude the contribution of central collisions to the production cross section the authors develop an impact parameter dependent equivalent photon method starting from the gamma gamma to H vertex for a scalar boson as well as for a pseudoscalar boson. For an assumed scalar Higgs mass of m_H=100 GeV they obtain a reduced cross section sigma _H=57 Pb for a Pb-Pb collision at LHC energies with gamma =3500 and sigma _H=450 Pb at SSC energies with gamma =8000, which are by a factor of 2.1 and 1.5 smaller than the corresponding original Weizsacker (1934)-Williams (1933) cross sections.

The S-wave spectrum of the q-bar²q² system composed of u and d quarks is investigated in the framework of the non-relativistic quark model using Bhaduri et al's potential (1981) supplemented with an effective interaction simulating the annihilation of qq pairs. The calculations are performed in harmonic oscillator bases including all the configurations up to 6h(cross) omega excitation energy. Some calculated 0⁺ and 2⁺ states are found to be compatible with the 0⁺ and 2⁺ rho rho and omega omega resonances observed in pn, gamma gamma and pi ^-p reactions. The q²q² interpretation of the isoscalar pi pi resonance AX(1565) is discussed.

The authors analyse double logarithmic asymptotics of gluon scattering without spin-flip and with parity exchange in the semi-hard Regge limit. The results are discussed with regard to the Regge behaviour of QCD amplitudes with quantum number exchange and to the small-x behaviour of polarized structure functions.

The authors analyse how corrections Delta V in the potential propagate in the two-body T-matrix. They investigate in detail the case in which V is approximated by a separable representation, so that the defect Delta V is defined as the difference between the exact potential and its separable expression. Two forms of the Gell-Mann and Goldberger (two-potential) formula are explored, which propagate the correction Delta V in the T-matrix in two different ways.

The nucleonic promiscuity factor P=N_pN_n/(N_p+N_n), where N_p(N_n) is the number of valence protons (neutrons) or holes, is shown to be a useful and physically meaningful parameter in the description of RMS charge radii. The introduction of P in the radius formula R approximately=R_c+0.07P/R_c (R_c; droplet model 'closed-shell radius') reduces the chi ²/n' value by a factor of three. The empirically found mass number dependence of the P-dependent contribution to radii is in agreement with the qualitative theoretical expectation for the average strength of the isoscalar p-n interaction. A significant correlation between surface diffusity and promiscuity as well as between diffusity and radius is pointed out.

The authors discuss two expressions for the density of kinetic energy, which differ by an integration by parts. the Wigner transform they show that the arithmetic mean of these two terms is closely analogous to the classical value. Harmonic oscillator wavefunctions are used to illustrate the radial dependence of these expressions. They study the differences they induce through effective mass terms when performing self-consistent calculations.

Low-lying bands arising out of the coupling of a g boson (hexadecupole vibration) to the SU(5), SU(3) and O(6) limits of the interacting boson model are classified. Closed analytic expressions for energies and E2 and E4 transition matrix elements are derived for the 1g-boson bands in each of the three limiting cases. These results are used in investigating the hexadecupole vibrational nature of some of the levels/bands in Cd, ¹⁵⁶Gd, ¹⁷⁸Hf and Os isotopes.

A gamma -ray spectroscopic study of the high spin states of the nucleus ¹⁵²Dy has been performed using the reaction ¹⁰⁸Pd(⁴⁸Ca,4n)¹⁵²Dy at a bombarding energy of 205 MeV. Gamma rays were detected using the TESSA3 multi-detector array. A set of discrete-line states forming a rotational band has been observed in the data and has been shown to extend up to a spin of around 60h(cross) and an excitation energy of about 30 MeV. The gamma -ray energy data are consistent with dynamic moment of inertia F⁽²⁾ of (85+or-3)h(cross)² MeV^-1, indicating a large quadrupole deformation. A measurement of the collectivity of the band has been made using the Doppler shift attenuation method, with the data for the lower spin states yielding a quadrupole moment of Q₀=(18+or-3) e b.

Gamma-ray transitions have been identified for the first time in ¹⁶⁴W. The yrast band has been established up to 28⁺(30⁺) and the alignment of the first pair of i_13/2 neutrons is observed at a rotational frequency h(cross) omega =0.29 MeV. Above h(cross) omega approximately 0.30 MeV the first pair of h_11/2 protons are observed to gradually align with a strong interaction strength. The systematics of the neutron alignment in nuclei ranging from Dy to W and with neutron numbers from 88 to 98 are discussed. The variations of alignment frequency with neutron and proton number are explained in terms of changes in quadrupole and hexadecapole deformation and the changing position of the Fermi surface in relation to the aligning neutron orbitals.

A phenomenological analysis of n-²⁰⁸Pb differential cross sections for elastic scattering has been performed over the neutron energy range 7.5-13.5 MeV using an optical model with a spherically symmetric central potential. The limitations of this model are explored by comparing the present results with those of a recent analysis of total cross sections. The authors demonstrate that with constant geometry this model fails to describe n-²⁰⁸Pb data adequately over this energy range and that this failure is associated only with the imaginary part of the central potential. Evidence is presented that this failure is a consequence of strong coupling between the ground state and collective excitations of ²⁰⁸Pb. In agreement with several structure calculations in the ²⁰⁸Pb region, the influence of low-lying collective states appears to be particularly important.

The production cross section of residual nuclei from the interaction of ²³⁸U and ²³²Th with 3.65 AGeV ¹²C ions has been studied by off-line gamma-ray spectroscopy. Mass-yield distributions were deduced from these data. The mass-yield curves show a large fission peak for 80<or approximately=A

Observations of cosmogenic nuclei (¹⁰Be and ¹⁴C) by a number of authors, and summarized by Kocharov et al. (1990), have drawn attention to the possibility of an increase in cosmic ray proton intensity over a period lasting several 10³ y some 30*10³ y ago. The authors examine the possibility that it represents the passage of a supernova remnant shock wave. They have shown previously, from studies in gamma ray astronomy, that SNR acceleration is a likely mechanism for the acceleration of cosmic ray protons in the GeV region. They conclude that the 'pulse' of protons responsible for the cosmogenic nuclei can, indeed, be explained in this way, although it is premature to make a definitive statement.

A search has been performed for large cluster breakup from ⁴⁰Ca following inelastic scattering. No evidence is seen for breakup to the ¹²C+²⁸Si, ¹⁶O+²⁴Mg or ²⁰Ne+²⁰Ne channels.

The authors, see Basu et al., ibid., vol.17, p.401, agree with the findings of Basu et al. that there are physical difficulties with a form factor analysis applied to maximally coupled interactions. However, their conclusions differ. They argue that clouds of virtual photons and other particles give rise to similar momentum dependencies for maximally coupled electron and proton vertices.