Polarization effects in the reaction $e^++e^-\to ρ^+ +ρ^- $ and determination of the $ρ-$ meson form factors in the time--like region

Abstract

The electron positron annihilation reaction into four pion production has been studied, through the channel $e^++e^-\to \bar ρ+ρ$. The differential (and total) cross sections and various polarization observables for this reaction have been calculated in terms of the electromagnetic form factors of the corresponding $γ^*ρρ$ current. The elements of the spin--density matrix of the $ρ-$meson were also calculated. Numerical estimations have been done, with the help of phenomenological form factors obtained in the space--like region of the momentum transfer squared and analytically extended to the time-like region.