Searching for the 5H resonance in the t + n + n system

The unbound hydrogen isotopes H-4,H-5 have been studied in the one-proton knockout channel of He-6 (240 MeV/u) impinging on a carbon target. The triton fragments originating from this channel were detected in coincidence with neutrons. Relative energy spectra as well as energy and angular correlations have been studied for the t + n and t + n + n systems. The analysis of the energy and angular correlations by the method of hyperspherical harmonic expansion allows to determine the relative weights of the most relevant partial waves in the three-body t + n + n final state. It is shown that the neutrons to a large extent occupy the p-shell and that the I-pi = 1/2(+) state is strongly populated as expected for the H-5 ground state. No evidence for a narrow resonance in the t + n + n system is obtained, instead a broad structure peaked at 3 MeV above the threshold with about 6 MeV as a full width at half maximum is observed. The two-body t + n system reveals a resonance compatible with earlier results for H-4. (C) 2003 Elsevier Science B.V. All rights reserved.