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The gamma -decay of excited states in the neutron-deficient nucleus ⁹³Rh has been observed for the first time. The fusion-evaporation reaction ⁵⁸Ni(⁴⁰Ca,3p2n)⁹³Rh at 187 MeV beam energy was used to produce ⁹³Rh. The multidetector array NORDBALL including particle selection was used for identification. From gamma gamma -coincidence data a decay scheme of 23 transitions up to high angular momentum was constructed for ⁹³Rh.

Isodoublet colour-octet scalar bosons appear in a natural extension of the minimal dynamical symmetry breaking model triggered by a tt condensate, which is geared to yield the top mass in the phenomenologically expected region. We study the effect of these bosons on oblique electroweak parameters S and T, and constrain the mass splitting between the neutral and the charged member of the colour octet. It is also shown that S can be substantially negative, depending on the way the masses in the coloured doublet are split.

In two recently proposed supersymmetric extended electroweak gauge models, the reduced Higgs sector at the 100 GeV energy scale consists of only two doublets, but they have quartic scalar couplings different from those of the minimal supersymmetric standard model. In the SU(2)*SU(2)*U(1) model, there is an absolute upper bound of about 145 GeV on the mass of the lightest neutral scalar boson. In the SU(3)*U(1) model, there is only a parameter-dependent upper bound which formally goes to infinity in a particular limit.

In this paper we compare the MSM predictions for Z-boson decay widths and the relevant ratios with new LEP data. We find that, among the parameters studied here, only the measured value of R_b exceeds that predicted in MSM by more than two standard deviations for m_t=174+or-16 GeV.

We present here detailed results on the multifractal structure analysis in one-dimensional ( eta or phi ) and two-dimensional ( eta - phi ) phase spaces for different nuclear targets in proton-emulsion nuclei interactions at 800 GeV. The multiplicity moments have a power-law dependence on the mean multiplicity in varying bin sizes in eta , phi and ( eta - phi ) spaces for different nuclear targets. The values of the generalized dimensions D_q are evaluated from the slopes for different phase spaces and targets. We find that D_q decreases with q for a given phase space and target. For fixed q the value of D_q increases with the target mass. The behaviour of D_q and the related spectrum typifies multifractality, thereby supporting a possible cascade mechanism in multiparticle production. The measure of inhomogeneity in the distribution, 1-D_q, decreases with multiplicity in an inverse ratio.

Exact expressions for the pi pi scattering lengths a₀ and a₂ in the mean-field approximation of the SU(2) Nambu-Jona-Lasinio model are derived. The results are given in closed form for arbitrary values of the pion mass. An expansion in terms of m_pi yields the Weinberg expressions to lowest order, whereas fixing m_pi and f_pi leaves the scattering lengths as functions of the constituent quark mass. Their variation with this quantity is displayed.

The level scheme of ¹⁵⁷Er has been extended from a spin region where the nucleus behaves as a prolate rotor to a region where the spin is produced by the alignment of all or most of the available valence nucleons along the symmetry axis of a weakly deformed oblate shape. The level scheme was established at high spin using up to four-fold gamma -ray coincidences detected in the Eurogam spectrometer following the reaction ¹¹⁴Cd(⁴⁸Ca,5n)¹⁵⁷Er at a bombarding energy of 210 MeV. Particularly favoured states have been established at I^K=69/2+, 81/2+, 71/2+, 77/2-, 87-/2 and 89-/2. Specific single-particle configurations are assigned to these special states by comparison with cranked Nilsson-Strutinsky calculations. These states are related to structures observed in the neighbouring nuclei ¹⁵⁸Er and ¹⁵⁷Ho. These data provide the spectrum of single-particle states for the lowest lying valence orbitals above the ¹⁴⁶Gd closed core.

Isotope shift measurements in 18 optical transitions between 8 samarium isotopes ^ASm have been taken (A=144, 146, 147, 148, 149, 150, 152, 154) using collinear laser ion beam spectroscopy. For the even-A isotopes, a direct-measurement technique was developed. A multidimensional King plot served to evaluate the term-related isotope shifts in the fine-structure multiplet 4f⁶(⁷F)5d⁸H_J. These shifts should show a linear dependence on J(J+1) in accordance with a crossed second-order approximation. A closer correlation is found between the isotope shifts and the fine-structure energies. Field shift and mass shift can be separated in order to calculate changes of mean-square charge radii delta (r²).

The Gamow-Teller matrix elements of 2 nu beta beta transitions to a 2₁⁺ final excited state has been calculated within the QRPA formalism for ⁷⁶Ge and ¹³⁶Xe. The relative stability of the calculation with respect to the particle-particle interaction strength is confirmed; on the other hand, the results are strongly dependent on the choice of the single-particle energy levels. A plausible explanation of such behaviour, originating in the interference of the individual contributions due to the third power of the energy denominator, has been proposed.

The symmetrical and nearly symmetrical break-ups of all naturally occurring nuclides have been classified as to relative probability by the ASAFM and the ranges of the two cold product fragments were calculated. The fragment ranges of 8.7 and 5.5 mu m in mica for respectively the two theoretically most probable disintegrations ¹⁷⁴Hf=⁸⁸Kr+⁸⁶Kr and ¹³⁰Ba=⁶⁶Ni+⁶⁴Ni fit well the 8.6 and 5.2 mu m radii of the two most abundant dwarf halo groups.

We devise two simple examples for the disassembly of hot nuclei: one uses a direct Monte Carlo method based on the atomic mass table and mass (charge) conservation; the other is a complete partition method based upon charge conservation only. Although the former is not physically complete and the latter is nearly a pure algebraic model, they give a qualitative correlation between the conditional moments of fragment charge distribution in the experimental disassembly of Au* and the fragment mass distribution in the percolation model. The results seem to indicate that it might be dangerous to regard the correlations of conditional moments as evidence of existing phase transitions.

The symmetric and asymmetric fission of the ⁵⁶Ni and ⁴⁸Cr rotating nuclei has been studied within the generalized liquid-drop model including the nuclear proximity energy. The selected shape sequence allows the rapid formation of a neck while keeping spherical ends. The potential barrier is a scission barrier standing at large deformations which hinders the fission process even at very high spins. Hyperdeformed minima appear at the foot of the fission barrier for sufficiently high angular momenta. These quasi-molecular configurations might correspond to some experimentally observed resonances at high angular momenta while, for lower spins, the fission barriers are sufficiently high and wide to allow fusion-fission phenomena.