Neutral pion electroproduction in $p(e,e'\pi^0)p$ above $\sqrt{s}>2$ GeV

TL;DR

This paper models neutral pion electroproduction above 2 GeV using Regge trajectory exchanges and dual resonance contributions, explaining experimental data from JLAB and HERMES across different kinematic regions.

Contribution

It introduces a comprehensive model combining Regge exchanges and dual resonance effects to describe neutral pion electroproduction above the resonance region.

Findings

Regge trajectory exchanges dominate at forward angles in photoproduction.

Resonance excitations explain high Q^2 electroproduction data.

Model successfully describes beam spin asymmetries at JLAB.

Abstract

Electroproduction of neutral pions in exclusive reaction $p(e,e'\pi^0)p$ is studied above the resonance region, $\sqrt{s}>2$ GeV. The reaction amplitude is described by exchanges of vector $\omega(782)$, $\rho(770)$ and axial-vector $h_1(1170)$ and $b_1(1235)$ Regge trajectories. The residual effect of $s$- and $u$-channel nucleon resonances is taken into account using a dual connection between the exclusive form factors and inclusive deep inelastic structure functions. In photoproduction at forward angles the exchange of Regge trajectories dominates and the dip region is filled by the resonances. In electroproduction the excitation of nucleon resonances explains the high $Q^2$ data from JLAB. The results for the beam spin azimuthal asymmetry measured at CLAS/JLAB are presented. Model calculations in the deep inelastic region at HERMES/DESY are given.