Three-body breakup of 11Li with the eikonal method

The Li-11 breakup on a Pb-208 target is studied in the Coulomb-corrected eikonal approximation by using a Li-9 + n + n three-body description of the projectile. The Li-11 wave functions are defined in the hyperspherical formalism for bound and scattering states and are obtained from effective Li-9 + n and n + n interactions. We first determine 0(+), 1(-), and 2(+) Li-9 + n + n phase shifts, which suggest the existence of a narrow 1(-) resonance near 0.5 MeV above threshold. The calculated breakup cross sections show a peak at low energies, in agreement with the data. The influence of monopole and quadrupole components is analyzed and shown to be non-negligible. We discuss the derivation of dipole strengths from experimental breakup cross sections and suggest that the simple Coulomb dipole approximation, traditionally used in the literature, should be replaced by more elaborate models. We also show that Li-11 + Pb-208 elastic scattering measurements would provide an indirect test of the model.