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

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.