Exclusive ${\pi}^0$ electroproduction at $W>2$ GeV with CLAS

TL;DR

This paper reports measurements of exclusive neutral-pion electroproduction at Jefferson Lab, providing detailed cross sections and structure functions over a wide kinematic range, and compares results with Regge and handbag theoretical models.

Contribution

It presents new experimental data on neutral-pion electroproduction at high energies and compares these results with advanced theoretical frameworks, highlighting the importance of transverse processes.

Findings

Transverse processes dominate the electroproduction mechanism.

Vector meson rescattering is essential in Regge model calculations.

Handbag models with transversity GPDs roughly match the data.

Abstract

Exclusive neutral-pion electroproduction ($ep\to e^\prime p^\prime \pi^0$) was measured at Jefferson Lab with a 5.75-GeV electron beam and the CLAS detector. Differential cross sections $d^4\sigma/dtdQ^2dx_Bd\phi_\pi$ and structure functions $\sigma_T+\epsilon\sigma_L, \sigma_{TT}$ and $\sigma_{LT}$ as functions of $t$ were obtained over a wide range of $Q^2$ and $x_B$. The data are compared with Regge and handbag theoretical calculations. Analyses in both frameworks find that a large dominance of transverse processes is necessary to explain the experimental results. For the Regge analysis it is found that the inclusion of vector meson rescattering processes is necessary to bring the magnitude of the calculated and measured structure functions into rough agreement. In the handbag framework, there are two independent calculations, both of which appear to roughly explain the magnitude of the structure functions in terms of transversity generalized parton distributions.