Scattering of the Halo Nucleus Be 11 on Au 197 at Energies around the Coulomb Barrier

Angular distributions of the elastic, inelastic, and breakup cross sections of the halo nucleus Be11 on Au197 were measured at energies below (Elab=31.9 MeV) and around (39.6 MeV) the Coulomb barrier. These three channels were unambiguously separated for the first time for reactions of Be11 on a high-Z target at low energies. The experiment was performed at TRIUMF (Vancouver, Canada). The differential cross sections were compared with three different calculations: semiclassical, inert-core continuum-coupled-channels and continuum-coupled-channels ones with including core deformation. These results show conclusively that the elastic and inelastic differential cross sections can only be accounted for if core-excited admixtures are taken into account. The cross sections for these channels strongly depend on the B(E1) distribution in Be11, and the reaction mechanism is sensitive to the entanglement of core and halo degrees of freedom in Be11.