Speaker
Description
We investigate electromagnetic properties of nucleons within the framework of an effective chiral theory derived from the QCD instanton vacuum. It was based on the nonlocal $2N_f$ quark interactions, which can be bosonized to be the nonlocal effective chiral action with the momentum-dependent dynamical quark mass. A great merit of this approach is that it does not have any adjustable free parameter, and provides a natural regulator to tame the divergent quark loops. On the other hand, the momentum-dependent quark mass causes the breaking of the gauge invariance. Having restored it, we obtain a so-called nonlocal contribution to the ordinary electromagnetic current. Using this current, we compute the electromagnetic form factors of the proton and neutron, as well as their charge and magnetization distributions. The results are in good agreement with the experimental data, and reveal unique features of the nonlocal interactions in both the electric and magnetic properties of the nucleon.