Unitarity constraints on meson electroproduction at backward angles

TL;DR

This paper explains large meson electroproduction cross sections at backward angles using unitarity constraints and meson coupling channels, aligning with Regge models and predicting outcomes for neutral pion production.

Contribution

It introduces a unitarity-based approach to meson electroproduction at backward angles, incorporating meson coupling channels and elastic re-scattering effects.

Findings

Explains large cross sections without disrupting Regge model agreement.

Accounts for disappearance of the node at moderate Q^2.

Provides predictions for neutral pion electroproduction.

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.