A. M. Moro

Elastic scattering and total reaction cross section for the 6He + 27Al system

Abstract The elastic scattering of the radioactive halo nucleus 6 He on 27 Al target was measured at four energies close to the Coulomb barrier using the RIBRAS (Radioactive Ion Beams in Brazil) facility. The Sao Paulo Potential (SPP) was used and its diffuseness and imaginary strength were adjusted to fit the elastic scattering angular distributions. Reaction cross-sections were extracted from the optical model fits. The reduced reaction cross-sections of 6 He on 27 Al are similar to those for stable, weakly bound projectiles as 6,7 Li, 9 Be and larger than stable, tightly bound projectile as 16 O on 27 Al.

Four-body continuum-discretized coupled-channels calculations using a transformed harmonic oscillator basis

The scattering of a weakly bound three-body system by a target is discussed. A transformed harmonic oscillator basis is used to provide an appropriate discrete and finite basis for treating the continuum part of the spectrum of the projectile. The continuum-discretized coupled-channels framework is used for the scattering calculations. The formalism is applied to different reactions, {sup 6}He+{sup 12}C at 229.8 MeV, {sup 6}He+{sup 64}Zn at 10 and 13.6 MeV, and {sup 6}He+{sup 208}Pb at 22 MeV, induced by the Borromean nucleus {sup 6}He. Both the Coulomb and nuclear interactions with a target are taken into account.

Long range absorption in the scattering of 6He on 208Pb and 197Au at 27 MeV

Quasi-elastic scattering of 6He at E_lab=27 MeV from 197Au has been measured in the angular range of 6-72 degrees in the laboratory system employing LEDA and LAMP detection systems. These data, along with previously analysed data of 6He + 208Pb at the same energy, are analyzed using Optical Model calculations. The role of Coulomb dipole polarizability has been investigated. Large imaginary diffuseness parameters are required to fit the data. This result is an evidence for long range absorption mechanisms in 6He induced reactions. Comment: 10 pages, 10 figures, minor corrections. To appear in Nucl. Phys. A

Three-body description of direct nuclear reactions: Comparison with the continuum discretized coupled channels method

The continuum discretized coupled channels (CDCC) method is compared with the exact solution of the three-body Faddeev equations in momentum space. We present results for (i) elastic and breakup observables of d+{sup 12}C at E{sub d}=56 MeV (ii) elastic scattering of d+{sup 58}Ni at E{sub d}=80 MeV, and (iii) elastic, breakup, and transfer observables for {sup 11}Be+p at E{sub {sup 11}Be}/A=38.4 MeV. Our comparative studies show that in the first two cases, the CDCC method is a good approximation of the full three-body Faddeev solution, but for the {sup 11}Be exotic nucleus, depending on the observable or the kinematic regime, it may miss some of the dynamic three-body effects that appear through the explicit coupling to the transfer channel.

Improved di-neutron cluster model for He-6 scattering

The structure of the three-body Borromean nucleus {sup 6}He is approximated by a two-body di-neutron cluster model. The binding energy of the 2n-{alpha} system is determined to obtain a correct description of the 2n-{alpha} coordinate, as given by a realistic three-body model calculation. The model is applied to describe the breakup effects in elastic scattering of {sup 6}He on several targets, for which experimental data exist. We show that an adequate description of the di-neutron-core degree of freedom permits a fairly accurate description of the elastic scattering of {sup 6}He on different targets.

Reexamining closed-form formulae for inclusive breakup: Application to deuteron- andLi6-induced reactions

The problem of the calculation of inclusive breakup cross sections in nuclear reactions is reexamined. For that purpose, the post-form theory proposed by Ichimura, Austern and Vincent [Phys. Rev. C32, 431 (1985) is revisited, and an alternative derivation of the non-elastic breakup part of the inclusive breakup is presented, making use of the coupled-channels optical theorem. Using the DWBA version of this model, several applications to deuteron and

Four-body continuum-discretized coupled-channels calculations

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Transfer to the continuum and breakup reactions

Li reactions are presented and compared with available data. The validity of the zero-range approximation of the DWBA formula is also investigated by comparing zero-range with full finite-range calculations.

Continuum-discretized coupled-channels calculations with core excitation

The development of a continuum-bin scheme of discretization for three-body projectiles is necessary for studies of reactions of Borromean nuclei such as {sup 6}He within the continuum-discretized coupled-channels approach. Such a procedure, for constructing bin states on selected continuum energy intervals, is formulated and applied for the first time to reactions of a three-body projectile. The continuum representation uses the eigenchannel expansion of the three-body S matrix. The method is applied to the challenging case of the {sup 6}He+{sup 208}Pb reaction at 22 MeV, where an accurate treatment of both the Coulomb and the nuclear interactions with the target is necessary.

Interplay between valence and core excitation mechanisms in the breakup of halo nuclei.

Abstract Reaction theory is an essential ingredient when performing studies of nuclei far from stability. One approach for the calculation of breakup reactions of exotic nuclei into two fragments is to consider inelastic excitations into the single particle continuum of the projectile. Alternatively one can also consider the transfer to the continuum of a system composed of the light fragment and the target. In this work we make a comparative study of the two approaches, underline the different inputs, and identify the advantages and disadvantages of each approach. Our test cases consist of the breakup of 11 Be on a proton target at intermediate energies, and the breakup of 8 B on 58 Ni at energies around the Coulomb barrier. We find that, in practice the results obtained in both schemes are in semiquantitative agreement. We suggest a simple condition that can select between the two approaches.