Unitarity constraints on meson electroproduction at backward angles

Abstract

At large virtuality $Q^2$, the coupling to the $\rho$ meson production channels provides us with a natural explanation of the surprisingly large cross section of the $\omega$, as well as the ${\pi }^{+}$, meson electroproduction recently measured at backward angles, without destroying the good agreement between the Regge pole model and the data at the real photon point. Together with elastic re-scattering of the outgoing meson it also provides us with a way to explain why the node, that appears at $u\sim -0.15$ GeV${}^2$ at the real photon point, disappears at moderate virtuality $Q^2$. Predictions are given for the electroproduction of the ${\pi }^0$ meson.

Comments: 14 pages, 19 figures. Version in press in Phys. Rev. C. A few slips corrected. Figure 11 frame customized References 10 and 14 corrected