Table of contents

The non-Abelian magnetic monopoles associated with symmetry breaking by the compactification of extra dimensions are considered. The author finds the monopole solution of the SU(2) gauge theory on M⁴*S¹. It is shown that the compactified space may blow up inside the monopoles.

A detailed examination of cosmic gamma rays indicates that the cosmic-ray intensity is somewhat lower in the region between Galactic spiral arms and the energy spectrum is steeper than in the surrounding regions. The results give support to the authors recent contention that processes within spiral arms-probably supernova remnants-are responsible for at least some of the acceleration experienced by cosmic rays.

The transverse component of the neutron polarisation, P_x', has been measured in the reaction gamma d to pn at energies E_gamma =0.3, 0.4 and 0.5 GeV and an angle theta _p*=50 degrees , using the analysing power of n-C elastic scattering. The results obtained for the double polarisation observable O_x' are compared with the prediction of partial-wave analysis.

The transverse component of the neutron polarisation in the reaction plane, P_x', has been measured for the reaction gamma p to pi ⁺n in the energy range E_gamma =0.75-1. GeV and for pion CM angles between 50 and 90 degrees . The neutron polarisation has been obtained from the asymmetry analysis of n-C elastic scattering. The results for the double polarisation observable O_x' are compared with phenomenological predictions.

The shapes of even-mass krypton nuclei are studied using a deformed Hartree-Fock calculation with the ⁵⁶Ni core. It is found that nuclei with A=72-80 are oblate in shape and ⁸²Kr is a transitional nucleus with near prolate oblate degeneracy. The low-lying states and the band crossing in ⁸²Kr are studied by angular momentum projection from the deformed configurations. The compression of energy levels near 6h is seen to be due to the rotation alignment of neutrons in g_9/2 orbits of oblate shape.

The transition from the resonance reaction mechanism at low level density to the direct reaction mechanism at high level density is investigated by means of numerical results obtained from microscopic calculations for nucleon induced reactions. The transition takes place rather sharply at Gamma approximately=D. Here, two types of motion of the nucleons exist simultaneously: a motion in long-lived states which are near equilibrium and a motion in short-lived states which are far from equilibrium. A formation of order out of chaos takes place only in the open quantum mechanical nuclear system. It is caused by quantum fluctuations via the continuum.

The interaction boson model in its IBM-4 version with only s bosons has been proposed to study the effects induced by the interplay between is vector and isoscalar components of the residual nuclear forces. The light nuclei are described in terms of R (L=0, S=1, T=0) and P bosons (L=0, S=0, T=1) according to the U(6) group structure. The possible subgroup chains, Casimir operators, bases and eigen energies of two limits have been found.

The positive and negative parity levels of odd-A Eu isotopes have been studied within the proton-neutron interacting boson-fermion approximation (IBFA-2) model. Calculated energy spectra, electromagnetic properties, changes in the mean square charge radii and one-nucleon transfer intensities are compared with experiment. A general good agreement is obtained with a small number of adjustable parameters.

The authors study the influence of the charge asymmetry degree of freedom on fission at small and very high mass symmetries. Using the condition of maximising the barrier penetrabilities, they compute the most probable decay channels for the cold fission of ²³⁴'²³⁶U, and compare the result with the experimental measurements.

Differential cross sections for charge pion production in the pA to pi X reaction have been measured at a proton kinetic energy of 1 GeV with a relative accuracy of 2-5% for the following targets: ¹H, ²D, ¹⁰B, ¹¹B, ¹²C, ¹⁶O, ²⁴Mg, ²⁵Mg, ²⁶Mg, ²⁷Al, ⁶⁴Cu, ¹¹⁶Sn, ¹²⁴Sn, ¹⁸¹Ta, ¹⁸⁴W and ²⁰⁸Pb. The measurements were performed with the help of two independent magnetic spectrometers with an angular acceptance of Delta Omega approximately=0.01 sr. The momentum resolution was equal to Delta P/P=1.4% in the range P=200-950 MeV/c at theta =0 degrees and Delta P/P=3% in the range P=75-600 MeV/sc at theta =57.8 degrees . The absolute normalisation of the cross sections was carried out using recent LNPI data on d sigma /d Omega for the pi ⁺d to pp reaction. The contribution of various mechanisms to the inclusive pion spectra is discussed.

The excitation functions of the ¹⁹⁷Au(( alpha ,n), ( alpha ,2n), ( alpha ,3n), (d,2pn), ( alpha , alpha n) and ( alpha , alpha 3n)) reactions were measured up to 75 MeV. The experimental data were compared with the calculated values obtained by means of a hybrid model (ALICE/85/300) using the initial exciton number n₀=4(4p0h) and the level density parameters a=A/8. A general agreement was found for all except the ( alpha , alpha n) and ( alpha , alpha 3n) reactions, where the disagreement was by about two orders of magnitude.

The coalescence model for complex-particle emission is modified by introducing corrections for the Coulomb barrier and the binding energy of the ejectile. The model is applied to the analysis of deuteron spectra for various projectile-target combinations at incident energies of 15-25 MeV/nucleon. The results, together with those of a previous analysis of alpha -particle spectra for the same colliding systems, show that the extracted coalescence radii decrease regularly with increasing A_p/(A_p+A_T) for both the weakly bound deuterons and the strongly bound alpha particles.

Analysis of emission of projectile and target fragments in ²²Ne+Ag(Br) collisions at 4.1A GeV/c is carried out to study peculiarities of particle 'sideward flow'. The possibility of determining the reaction plane is considered. 'Bounce-off' of ²²Ne projectile fragments is observed by investigating their projections onto the reaction plane. The angular distribution of slow fragments has a maximum which is due to 'side splash'. By studying projections onto the azimuthal plane, data on 'sideward flow' are obtained. An increase of ranges is observed for slow fragments emitted in the direction of the 'side splash'.

A general program is being developed for the systematic and careful evaluation of Green functions in pion-nucleon problems. This paper is the first in a series of projects involving integral method for the calculation of the pion and nucleon propagators. A method is presented for evaluating efficiently and accurately integrals of the form integral r^m chi _l1(k₁r) chi _l2(k₂r). . . chi _ln(k_nr) dr, where m and n are arbitrary integers and chi _l(x) can be either a spherical Bessel function, j_l(x), or a spherical Neumann function, n_l(x). The range of integration depends upon the particular problem encountered. The prototype integral studied is I_ll'L(kk'P) identical to integral ₀^infinity r²j_l(kr) j_l'(k'r)j_L(pr)dr whose integrand for large r has a slowly decreasing oscillatory behaviour. Rapid convergence is ensured by rotating, in the complex plane, the upper part of this integral, giving an integrand which decreases exponentially. A scaling formula is used to evaluate I_ll'L(kk'p) for very small or very large values of the momenta. Also, it is shown that, if l, l' and L satisfy triangular inequalities and if l+l'+L is even, then k, k' and p must also satisfy triangular inequalities, which is the condition required by the vector delta function delta (k+k'-p). Finally the authors present sum rules and integral relations for I_ll'L(kk'p).

For pt.I see ibid., vol.14, p.973(1988). Products of Green functions for pion-nucleon interactions can most naturally be evaluated by transformation to a momentum-space representation. Such transformations often involve an integral whose integrand is highly oscillatory. By deforming the contour of integration in the complex plane, such an integral can be made to converge rapidly. All oscillatory terms are converted into pure damping terms which decrease exponentially. Examples are given for simple integrals, for the integral of three spherical Bessel functions, and for the Fourier and spherical Bessel function transforms of the Woods-Saxon potential (Fermi-Dirac distribution function). They authors also show that oscillatory principal-value integrals can usually be accurately evaluated using this method. Convergence with respect to the number of Gaussian points is studied. It is shown that the method normally converges much better than ordinary integration along the real axis, especially as the frequency of the oscillations increases relative to the damping. A comparison is made with the method of steepest descent.

Low-lying states have been investigated in the neutron-deficient nuclei ^138,140Gd and ¹³⁹Eu. The states were populated using the ⁹²Mo+⁵⁰Cr and ⁹²Mo+⁵⁴Fe reactions. New energy levels are reported in each nucleus and mean lifetimes have been measured in ¹³⁸Gd and ¹³⁹Eu. The deformations deduced from the experiments confirm the predicted trend to higher deformation for the more neutron-deficient nuclei. The N=76 isotope (¹³⁹Eu and ¹⁴⁰Gd) show evidence for band crossing involving h_11/2 neutrons and protons.