Comparative study of the selectivity displayed by (6Li,d) and (16O, 12C) reactions

Four-particle-transfer processes induced by the (⁶Li, d) and (¹⁶O, ¹²C) reactions to strongly excited 0⁺ states are compared. Although the selectivity displayed by these reactions is similar, the corresponding relative cross sections are rather different. These results emerge naturally from a simple microscopic model.     

Neutral pion production in subthreshold heavy ion collision with16O (38 MeV/u) and20Ne (200 MeV/u) beams

Inclusive production of neutral pions has been studied in¹⁶O +²⁷Al,¹⁹⁷Au reactions at 38 MeV/u and²⁰Ne +²⁷Al reaction at 200 MeV/u. A setup of 10 Pb glass Cherenkov detector telescopes was used to detect the twoγ rays from theπ ⁰ decay.     

Nuclear multifragmentation, percolation, and the fisher droplet model: common features of reducibility and thermal scaling

It is shown that the Fisher droplet model, percolation, and nuclear multifragmentation share the common features of reducibility (stochasticity in multiplicity distributions) and thermal scaling (one-fragment production probabilities are Boltzmann factors). Barriers obtained, for cluster production on percolation lattices, from the Boltzmann factors show a power-law dependence on cluster size with an exponent of 0.42+/-0.02. The EOS Collaboration Au multifragmentation data yield barriers with a power-law exponent of 0.68+/-0.03. Values of the surface energy coefficient of a low density nuclear system are also extracted.     

Lambda spectra in 11.6A GeV/c Au-Au collisions

E896 has measured Lambda production in 11.6A GeV/c Au-Au collisions over virtually the whole rapidity phase space. The midrapidity p(t) distributions have been measured for the first time at this energy and appear to indicate that the Lambda hyperons have different freeze-out conditions than protons. A comparison with the relativistic quantum molecular dynamics model shows that while there is good shape agreement at high rapidity the model predicts significantly different slopes of the m(t) spectra at midrapidity. The data, where overlap occurs, are consistent with previously reported measurements.     

An approach to the nuclear many-body problem including virtual mesons (I). HF approximation in finite nuclei

A method is presented allowing a self-consistent treatment of meson dynamics in finite nuclei. The single-nucleon self-energy is derived in the framework of the HF approximation. The differences with respect to the usual (static) HF approach are the energy dependence of the self-energy and the appearance of a new term, and both are due to the time delay in meson propagation. The first effect introduces a double self-consistency condition on both the single-particle energies and wave functions. The reported results on the ¹²C and ¹⁶O nuclei show the importance of the correct treatment of meson degrees of freedom.     

Microscopic structure of monopole and quadrupole bosons

Within the pairing-plus-quadrupole model the wave function of the intrinsic state will be described as a product of basic fermion pairs, which are a linear combination of correlated monopole and quadrupole pairs only. The microscopic structure of these S- and D-pairs, as well as the mixture coefficient between them, are determined by minimizing the total energy within the field approximation. While the mixture between monopole and quadrupole pairs changes drastically to account for the transition from sphericity to static deformation, their internal structure remains fairly constant when varying the number of particles.     

Inclusive (p, π0) reactions atE lab=200 MeV

Zeitschrift für Physik A Hadrons and nuclei - The inclusive production of neutral pions has been studied with a proton beam atE lab =200 MeV. The twoγ rays from theπ 0 decay were...     

Anisotropic α decay

A microscopic approach to the problem of anisotropic α decay in deformed nuclei is presented. Nuclear wave functions are calculated within the BCS approach, and the WKB semiclassical approximation is used for the penetration through the deformed Coulomb barrier. Results are compared with recent experimental data obtained at CERN by the ISOLDE and NICOLE collaborations. The predictions of the model for well-deformed nuclei are in very good agreement with experimental findings.