Low-energy 11Li +p and 11Li +d scattering in a multicluster model

The Li-11 +p and Li-11 +d reactions are investigated in the continuum discretized coupled channel (CDCC) method with a three-body description (Li-9 +n+n) of Li-11. I first discuss the properties of Li-11, and focus on E1 transition probabilities to the continuum. The existence of a 1(-) resonance at low excitation energies is confirmed, but the associated E1 transition from the ground state does not have an isoscalar character, as suggested in a recent experiment. In a second step, I study the Li-11 +p elastic cross section at E-lab = 66 MeV in the CDCC framework. I obtain a fair agreement with experiment, and show that breakup effects are maximal at large angles. The breakup cross section is shown to be dominated by the 1(-) dipole state in Li-11, but the role of this resonance is minor in elastic scattering. From CDCC equivalent Li-11 +p and Li-11 +n potentials, I explore the Li-11 +d cross section within a standard three-body Li-11 +(p + n) model. At small angles, the experimental cross section is close to the Rutherford scattering cross section, which is not supported by the CDCC. A five-body (Li-9 +n+n) + (p + n) calculation is then performed. Including breakup states in Li-11 and in the deuteron represents a numerical challenge for theory, owing to the large number of channels. Although a full convergence could not be reached, the CDCC model tends to overestimate the data at small angles. I suggest that measurements of the Li-9 +p elastic scattering would be helpful to determine more accurate optical potentials. The current disagreement between experiment and theory on Li-11 +d scattering also deserves new experiments at other energies.