Nucleon electric polarizability in a non-relativistic chiral constituent quark model

The non-relativistic chiral constituent quark model is applied to study nucleon electric polarizability and its electric mean square radius. The effect of Goldstone Boson degrees of freedom is discussed explicitly. It is found that chiral fields remarkably contribute not only to the proton and neutron electric mean square radii, but also to their electric polarizabilities. Consequently, the fluctuation of the chiral fields inside the nucleon cannot be simply ignored in the explanation of nucleon intrinsic polarizabilities, as well as in other predictions of the nucleon spin and flavor properties. Moreover, if we keep the harmonic oscillator frequency ω to be around 500 MeV, we find that the simple model with the Goldstone boson degrees of freedom is not sufficient to give a good description both for the electric mean square radii and for the electric polarizabilities of the proton and neutron simultaneously, even if the configuration mixing is included. Our results show that a small value of ω∼300 MeV is favored.