Nucleon Tensor Charge from Exclusive $\pi^o$ Electroproduction

TL;DR

This paper proposes using exclusive π⁰ electroproduction to extract the nucleon tensor charge and transversity-related quantities, connecting experimental observables to underlying quark helicity flip distributions through hadronic and partonic models.

Contribution

It introduces a novel method to access the nucleon tensor charge via π⁰ electroproduction, linking experimental data to chiral odd generalized parton distributions and Regge exchange models.

Findings

Tensor charge can be extracted from π⁰ electroproduction data.

The process isolates C-parity odd and chiral odd quantum number combinations.

Model calculations suggest measurable cross sections and asymmetries related to transversity.

Abstract

Exclusive $\pi^o$ electroproduction from nucleons is suggested for extracting the tensor charge and other quantities related to transversity from experimental data. This process isolates C-parity odd and chiral odd combinations of t-channel exchange quantum numbers. In a hadronic picture it connects the meson production amplitudes to C-odd Regge exchanges with final state interactions. In a description based on partonic degrees of freedom, the helicity structure for this C-odd process relates to the quark helicity flip, or chiral odd generalized parton distributions. This differs markedly from deeply virtual Compton scattering, and both vector meson and charged $\pi$ electroproduction, where the axial charge can enter the amplitudes. Contrarily the tensor charge enters the $\pi^o$ process. The connection through the helicity description of the process to both the partonic and hadronic perspectives is studied and exploited in model calculations to indicate how the tensor charge and other transversity parameters can be related to cross section and spin asymmetry measurements over a broad range of kinematics.