Four-body calculation of 6He breakup with the Coulomb-corrected eikonal method

The elastic breakup of a three-body projectile on a target is studied within the eikonal approximation with full account of final-state interactions. Bound and scattering states are calculated in hyperspherical coordinates on a Lagrange mesh. A correction is introduced to avoid the divergence of breakup cross sections due to the Coulomb interaction. The eikonal approximation allows the direct calculation of various cross sections, and in particular multidifferential cross sections can be obtained. The model is applied to the breakup of He-6 on Pb-208. The He-6 halo nucleus is described within a three-body alpha+n+n model involving effective alpha n and nn interactions. The eikonal phase is obtained from optical potentials between alpha and n, and the target. Around 0.8 MeV, the total breakup cross sections exhibit a narrow 2(+) resonant peak superimposed over a broad bump corresponding to a 1(-) resonance. These results suffer from a disagreement with experimental data at 240 MeV/nucleon, where cross sections are much smaller at low energies. The obtained E1 strength distribution resembles other theoretical results and reopens a long-standing problem about the existence of a 1(-) low-energy resonance in the He-6 continuum.