The three-body breakup reactions induced by 47-MeV protons on a gaseous ${\mathrm{He}}^4$ target have been investigated in a kinematically complete experiment. Protons were observed in coincidence with tritons or ${\mathrm{He}}^{3,}$s at several pairs of coplanar lab angles using two counter telescopes. Data were stored by an on-line computer which serially listed four linear signals from each event on magnetic tape. The proton spectra showed strong enhancements from neutron-proton and proton-proton final-state interactions, in agreement with the predictions of the Watson-Migdal theory. A Chew-Low-type extrapolation procedure was used to extract the $\mathrm{np}$ singlet scattering length, which was in fair agreement with the value from $\mathrm{np}$ free scattering. The triton and ${\mathrm{He}}^3$ spectra showed peaks due to sequential reaction processes via the continuum resonance states in the ${\mathrm{He}}^4$ system. These enhancements could be identified with previously observed ${\mathrm{He}}^4$ levels of known spin and parity assignments.

• Received 17 April 1970

DOI:https://doi.org/10.1103/PhysRevC.2.828