Quark-hadron duality sum rules for spin-dependent photon-nucleon and photon-photon resonance cross-section

Abstract

We focus on the special kind sum rules, namely, the relativistic dipole-moment-fluctuation sum rules with only main valence quark configuration of hadrons taken into account and stress the specifics of these sum rules enabling to treat them as the quark-hadron duality sum rules in the processes initiated by real photons. A few relations, including the sum rule for the neutron charge radius, are discussed between different bremsstrahlung-weighted integrals of the nucleon resonance photoexcitation cross sections and correlation functions of the quark electric dipole moment operators in the nucleon ground state. These functions are of interest for checking detailed quark-configuration structure of the nucleon state vector. In the meson sector, we mainly discuss the sum rules for the two-photon decay widths of the pseudoscalar mesons made of heavy charm quarks that are of the present interest. The obtained results are compared with predictions of other approaches.