A two-pion exchange three-nucleon force based on a realistic pi N interaction

The contribution of a pi pi-exchange three-body force to the three-nucleon binding energy is calculated in terms of a pi N amplitude. The latter is ba sed on a meson-theoretical model of pi N interaction developed by the Julic h group. Similar to a previous study based on simple phenomenological pi N potentials a very small effect of the resulting three-body force is found. Possible origins of the two-orders-of-magnitude discrepancy between the pre sent result and the values obtained for the Tucson-Melbourne three-body for ce are investigated. Evidence is provided that this discrepancy is most lik ely due to strikingly different off-shell properties of the pi N amplitudes underlying the two approaches.