Neutron Momentum Distributions from “Core Break-Up” Reactions of Halo Nuclei

Neutron angular distributions from violent break-up reactions of 11Li and 11Be have been measured at 28 MeV/u and 280 MeV/u and at 41 MeV/u and 460 MeV/u, respectively. The derived neutron momentum distributions show a narrow component in transverse momentum that is within uncertainties independent of beam energy and target charge. This component is suggested to be simply related to the momentum distribution of the loosely bound halo neutron(s) in the projectiles.