Neutron correlation studies in the Borromean nucleus 6He

The availability of radioactive ion beams has brought in new areas of interesting physics. In this talk we describe an elaborate experiment with the aim of determining the differential cross sections for one- and two-neutron transfer reactions with the Borromean nucleus 6He on 65Cu at Elab=22.6 MeV. Triple coincidences (α, n1, γ) were made using a high efficiency detection setup and beam intensities ∼2x107 ples/s. Since the eventual reaction products after 1n and 2n transfer are identical, a subtractive method was employed to extract the cross sections. The result obtained is that the cross sections for 2n transfer are about an order of magnitude larger than for 1n transfer, implying the predominance of the di-neutron over the cigar configuration of 6He. CRC calculations for elastic scattering, 1n and 2n transfer were made. The elastic scattering and the 1n transfer angular distribution were reproduced to a reasonable degree. For 2n transfer, as the level information for 67Cu is not available, we used instead the levels of 65Cu. The calculations with this assumption reproduced the trend of the data. (author)