Deep exclusive electroproduction of $\pi^0$ at high $Q^2$ in the quark valence regime

TL;DR

This paper presents measurements of exclusive neutral pion electroproduction at high momentum transfer, revealing the dominance of transversely polarized virtual photon amplitudes and supporting models involving transversity GPDs and pion distribution amplitudes.

Contribution

It provides new experimental data on neutral pion electroproduction at high $Q^2$, supporting the role of transversity GPDs in nucleon structure analysis.

Findings

Transverse virtual photon amplitudes dominate cross sections.

Data agree with transversity GPD-based theoretical calculations.

Results offer insights into nucleon structure via pion production.

Abstract

We report measurements of the exclusive neutral pion electroproduction cross section off protons at large values of $x_B$ (0.36, 0.48 and 0.60) and $Q^2$ (3.1 to 8.4 GeV$^2$) obtained from Jefferson Lab Hall A experiment E12-06-014. The corresponding structure functions $d\sigma_L/dt+\epsilon d\sigma_T/dt$, $d\sigma_{TT}/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{LT'}/dt$ are extracted as a function of the proton momentum transfer $t-t_{min}$. The results suggest the amplitude for transversely polarized virtual photons continues to dominate the cross-section throughout this kinematic range. The data are well described by calculations based on transversity Generalized Parton Distributions coupled to a helicity flip Distribution Amplitude of the pion, thus providing a unique way to probe the structure of the nucleon.