ORIGINS OF SPIN-ORBIT-SPLITTING IN N-15

The spin-orbit splitting of the p1/2 and p3/2 hole states in N-15 is s tudied with realistic nuclear forces and the variational cluster Monte Carlo method. The results show that the two-nucleon L.S forces give a pproximately half of the observed splitting, while the other half come s from pion exchange interactions between three or more nucleons. The observed splitting is fairly well reproduced by these calculations bas ed on nonrelativistic nuclear many-body theory.