Unitarity constraints on neutral pion electroproduction

TL;DR

This paper explains the large neutral pion electroproduction cross section at high virtuality using unitarity constraints and vector meson channels, reconciling experimental data with theoretical models.

Contribution

It introduces a unitarity-based approach to account for high-$Q^2$ electroproduction data, connecting vector meson channels and rescattering effects.

Findings

Vector meson production channels explain large cross sections.

Elastic rescattering accounts for the disappearance of the diffraction node.

Model maintains agreement with data at real photon point.

Abstract

At large virtuality $Q^2$, the coupling to the vector meson production channels provides us with a natural explanation of the surprisingly large cross section of the neutral pion electroproduction recently measured at Jefferson Laboratory, without destroying the good agreement between the Regge pole model and the data at the real photon point. Elastic rescattering of the $\pi^0$ provides us with a way to explain why the node, that appears at $t\sim -0.5$ GeV$^2$ at the real photon point, disappears as soon as $Q^2$ differs from zero.