Three-Body Breakup Of He-6 And Its Halo Structure

The Borromean halo nucleus He-6 has been studied by a kinematically complete measurement of Coulomb and nuclear breakup into alpha + 2n on Pb and C targets at 70 MeV/nucleon. Fully quantum-mechanical four-body breakup calculations reproduce the energy and angular differential cross sections below E-rel similar to 1 MeV for both targets. The model used here reproduces the He-6 ground-state properties as well as alpha-n and n-n scattering data and predicts an average opening angle of 68 degrees between the two halo neutrons. However, the model underestimates the breakup cross sections for higher E-rel, indicating a possible contribution from the inelastic breakup. Alternatively, we examine the empirically modified calculations that reproduce the energy-differential cross sections for a wide range of scattering angles for both targets. The extracted B(E1) peaks at E-rel similar to 1.4 MeV and amounts to 1.6(2) e(2) fm(2) for E-rel <= 20 MeV, resulting = 56(-10)(+9) degrees. In either interpretation, the current results show evidence of the dineutron spatial correlation in He-6. (C) 2021 The Author(s). Published by Elsevier B.V.