Mitsuru Sakuraoka

Unified treatment of photon and massive vector-meson scattering process by helicity amplitudes

Abstract A formalism to treat virtual photons and massive vector mesons on the essentially same footing is developed to include the scattering of a massless and massive spin-1 particle by a spin - 1 2 particle . It is explicitly shown that a smooth limit of the massive case amplitudes to the Compton amplitudes can be realized within the framework of helicity amplitudes and that the zero-mass limit satisfies all the requirements of gauge invariance. Such a formalism is advantageous to incorporate the vector-dominance hypothesis and yields a convenient parametrization of helicity amplitudes for the Regge-pole analysis of real and virtual photon processes.