Dipole polarizabilities of light pseudoscalar mesons within the domain model of the QCD vacuum

Abstract

Dipole polarizabilities of light pseudoscalar mesons are calculated in the framework of the mean field approach to QCD vacuum and bosonization based on the statistical ensemble of almost everywhere homogeneous Abelian (anti-)self-dual gluon fields, the domain model of QCD vacuum. In this approach, a nonlocal effective action of meson fields is derived that describes all possible strong, weak, and electromagnetic interactions of meson fields including their excited states. The considered mean field implements confinement and chiral symmetry, which manifests itself both in the properties of quark and gluon fields as well as upon bosonization, in the mass spectrum, decays constants and form factors of nonlocal colorless hadrons, and leads to the qualitatively distinctive features of the effective meson action. Particularly relevant to the subject of the present paper are the nonlocality of meson-quark-antiquark vertices and the absence of poles at real momenta in the propagators of scalar meson fields composed of light quark-antiquark pairs. In view of this, studying the role of manifest nonlocality of mesons and contribution of intermediate scalar meson fields in formation of the polarizabilities is of special interest. It turns out that, for charged pions and kaons, this contribution is substantial but not the largest one. Nonlocal nature of mesons provides an additional contribution so that calculated polarizabilities are in reasonable agreement with COMPASS experimental data and chiral perturbation theory.