Spin-orbit coupling for Λ--4He scattering using a one-boson-exchange model for the ΛN interaction. II

The polarization P_Λ(θ) and differential cross section dσ/dΩ for Λ–⁴He scattering are calculated for Λ incident energies 5–20 MeV, for the Λ–⁴He spin-orbit potentials V_LS derived from several one-boson-exchange models given for the ΛN interaction in the literature. The Λ–⁴He central potential used depends on the intrinsic range b for the ΛN potential; our knowledge of this parameter is reviewed, and the estimate b=2.0±0.3 fm is obtained for a Gaussian shape from a simplified analysis of the low-energy ΛN cross-section data. The effect on V_LS of a cutoff in the ΛN spin-orbit potential for distances r_ΛN ≤ d is discussed and compared with the regularization adopted in the earlier paper. P_Λ(θ) and dσ/dΩ for the modified V_LS with d=0.4 fm are compared with those for the case d=0; the sensitivity of the largest p-wave phase shift and of P_Λ(θ) to the intrinsic range b is also indicated. The relation between these V_LS calculations and the effect of ΛN spin-orbit forces in the shell-model analysis of the Λ separation energies for the p-shell Λ hypernuclei is discussed; since the latter prefers V_LS with sign opposite that calculated here, P_Λ(θ) has been calculated also for the spin-orbit potential (−V_LS) to illustrate that the sign appropriate for the ΛN spin-orbit interaction could be settled by even rough measurements over wide energy and angular intervals in this low-energy region.