Breakup reactions of the one-neutron halo nucleus 11 Be on lead and carbon targets at about 70 MeV/nucleon have been investigated at RIKEN by measuring the momentum vectors of the incident 11 Be, outgoing 10 Be, and neutron in coincidence. The relative energy spectra as well as the angular distributions of the 10 Be+n center of mass system (inelastic angular distributions) have been extracted both for Pb and C targets. For the breakup of 11 Be on Pb, the selection of forward scattering angles, corresponding to large impact parameters, is found to be effective to extract almost purely the first-order E1 Coulomb breakup component, and to exclude the nuclear contribution and higher-order Coulomb breakup components. This angle-selected energy spectrum is thus used to deduce the spectroscopic factor for the 10 Be(0 + ) ⊗ ν2s 1/2 configuration in 11 Be which is found to be 0.72 ± 0.04 with a B(E1) strength up to Ex = 4 MeV of 1.05 ± 0.06 e 2 fm 2 . The energy weighted E1 strength up to Ex = 4 MeV explains 70 ± 10 % of the cluster sum rule, consistent with the obtained spectroscopic factor. The non-energy weighted sum rule within the same energy range is used to extract the root mean square distance of the halo neutron to be 5.77( 16) fm, consistent with previously known values. In the breakup with the carbon target, we have observed the excitations to the known unbound states in 11 Be at Ex = 1.78 MeV and Ex = 3.41 MeV. Angular distributions for these states show the diffraction pattern characteristic of L=2 transitions, resulting in J π =(3/2,5/2) + assignment for these states. We finally find that even for the C target the E1 Coulomb direct breakup mechanism becomes dominant at very forward angles.

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The p((11)Li, (9)Li)t reaction has been studied for the first time at an incident energy of 3A MeV at the new ISAC-2 facility at TRIUMF. An active target detector MAYA, built at GANIL, was used for the measurement. The differential cross sections have been determined for transitions to the (9)Li ground and first excited states in a wide range of scattering angles. Multistep transfer calculations using different (11)Li model wave functions show that wave functions with strong correlations between the halo neutrons are the most successful in reproducing the observation.

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