Λ spin-orbit splitting in heavy hypernuclei as deduced from DWIA analyses of the 89Y(π+, K+)89ΛY reaction

By taking nuclear core excitations into account, detailed structure calculations of (89)(Lambda)Y have been performed as a function of the A spin-orbit splitting. The obtained wave functions have been used to estimate the (pi(+), K(+)) reaction cross sections within the distorted-wave impulse approximation (DWIA). A theoretical explanation is given quantitatively for the first time of how to understand the doublet substructure of each major peak observed in medium-heavy hypernuclear production. A small Lambda spin-orbit splitting of around delta(0 f(Lambda)) = 0.2 MeV is deduced, a value consistent with the small Lambda N two-body spin-orbit interactions deduced from gamma-ray measurements in three light hypennuclei. (D 2008 Elsevier B.V. All rights reserved.