A generalized unitary pole approximation concerning the three-body amplitudes in the kernel of four-body integral equations is introduced. We furthermore study the dependence of the ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ binding energy and of four-body cross sections upon a position-space cut-off parameter in the effective interactions.

• Received 27 July 1977

DOI:https://doi.org/10.1103/PhysRevLett.39.788