Quark Contribution to the Nucleon Polarizabilities and Three-Body Forces

Abstract.

 Lower and upper bounds to the electric polarizability and para-magnetic susceptibility are explicitly calculated by means of a sum-rule technique and within a large variety of constituent quark models. The role of three-body forces in the potential model is investigated in detail as well as the effects of SU(6) breaking terms. The quark degrees of freedom give a quite sizeable contribution to the static polarizability and the meson cloud accounts roughly for 30% and 60% of the electric proton and neutron polarizability respectively. The quark contribution to the paramagnetic susceptibility is even higher and the mesonic effects are rather uncertain.