Neutron-neutron effective range parameters from the 3H(2H, 3He)2n and 3He(2H, 3H)2p reactions

Abstract

The energy spectra of 3 H and 3 He nuclei from the 3 He( 2 H, 3 H)2p, 3 H( 2 H, 3 He)2n, 3 He( 2 H, 3 He)pn and 3 H( 2 H, 3 H)pn reactions were measured between 6° and 20° at a bombarding energy of 11 MeV. An upper limit of 5 μb sr was determined for the cross section for producing a bound di-neutron at 6° and 7.5°. The 3 H( 2 H, 3 He)2n and 3 He( 2 H, 3 H)2p data together with previous measurements at higher energies have been used to investigate the reliability of information obtained about the two-nucleon system from such three-body final state reactions. As an aid to these investigations, we have made Born approximation calculations employing realistic nucleon-nucleon potentials and an antisymmetrized final state wave function for the five-particle system. These calculations reproduce many of the features observed in the experimental data and indicate that the role of complex exchange processes cannot be ignored. The results show that previous attempts to obtain information on the neutron-neutron effective range parameters from the 3 H( 2 H, 3 He)2n reaction may have seriously overestimated the accuracy that could be obtained.