The Compton scattering on a charged pion and the process γγ → π 0 π 0 are studied using the dispersion relations. Unknown parameters of σ meson and a sum and a difference of the π 0 polarizabilities are found from a fit to the experimental data for γγ → π 0 π 0 process. The found parameters of the σ meson are used for the calculation of the cross section of the elastic γπ ± scattering. The anal...

We revisit sidewise dispersion relations as a method to relate the nu-cleon off-shell form factor to observable quantities, namely the meson-nucleon scattering phase shifts. It is shown how for meson-nucleon scattering a re-definition of the intermediate fields leaves the scattering amplitude invariant, but changes the behavior of the off-shell form factor as expressed through dispersion relati...

We compare results of our studies [1,2] on vector meson production within the QCD factorization at next-to-leading order with HERA data. 1 Introduction The exclusive vector meson V electro-and photo-productions in photon-proton collisions , γ p → V p, are the subject of HERA collider experiments. The primary motivation for the interests in these processes, both for the light ρ−meson electro-pro...

Using ideas underlying the flavour-blind “Nijmegen Unitarised Meson Model” (NUMM) [1, 2, 3] we try to understand on the basis of a system of Schrödinger equations with one mesonmeson and one (spinless) quark-antiquark channel coupled by a simple delta-shell transition potential the formation of (e.g. scalar) meson-meson scattering singularities in the complex momentum and energy plane. Surprisi...