Three-body halos. V. Computations of continuum spectra for Borromean nuclei

We solve the coordinate space Faddeev equations in the continuum. We employ hyperspherical coordinates and provide analytical expressions allowing easy computation of the effective potentials at distances much larger than the ranges of the interactions where only s-waves in the different Jacobi coordinates couple. Realistic computations are carried out for the Borromean halo nuclei 6He (n+n+\alpha) for J\pi = 0+-, 1+-, 2+- and 11Li (n+n+9Li) for (1/2)+-, (3/2)+-, (5/2)+-. Ground state properties, strength functions, Coulomb dissociation cross sections, phase shifts, complex S-matrix poles are computed and compared to available experimental data. We find enhancements of the strength functions at low energies and a number of low-lying S-matrix poles.Comment: 35 pages, 14 figure

Invariant mass spectrum and #alpha# - n correlation function studied in the fragmentation of "6He on a carbon target

Momentum distributions and invariant mass spectra from the breakup of "6He ions with an energy of 250 MeV/u interacting with a carbon target have been studied. The data were used to extract information about the reaction mechanism which is influenced by the structure of "6He. It is found that the dominant reaction mechanism is a two-step process: knock out of one neutron followed by the decay of the "5He resonance. The shape of the (#alpha#+n) two-body invariant mass spectrum is interpreted as mainly reflecting the "5He ground state which is a J "#pi# =3/2"- resonance. However, no evidence for correlations between #alpha# particles and neutrons is observed in the momentum widths of the distributions. It is demonstrated that a combined analysis of the two-body invariant mass spectrum and an appropriate correlation function may be used to determine the properties of the intermediate resonance. (orig.)Available from TIB Hannover: RO 801(97-61) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman