Beam Spin Asymmetry in Electroproduction of Pseudoscalar or Scalar Meson Production off the Scalar Target

TL;DR

This paper presents a theoretical analysis of beam spin asymmetry in electroproduction of scalar and pseudoscalar mesons off scalar targets, highlighting the model-independent relations and potential for probing hadronic structure.

Contribution

It provides a general formulation of the differential cross section involving hadronic form factors and discusses how beam spin asymmetry measurements can reveal hadronic and GPD contributions.

Findings

No beam spin asymmetry for pseudoscalar mesons.

Potential to explore imaginary parts of hadronic amplitudes.

Opportunity to examine chiral-odd GPD contributions.

Abstract

We discuss the electroproduction of pseudoscalar ($0^{-+}$) or scalar ($0^{++}$) meson production off the scalar target. The most general formulation of the differential cross section for the $0^{-+}$ or $0^{++}$ meson production process involves only one or two hadronic form factors, respectively, on a scalar target. The Rosenbluth-type separation of the differential cross section provides the explicit relation between the hadronic form factors and the different parts of the differential cross section in a completely model-independent manner. The absence of the beam spin asymmetry for the pseudoscalar meson production provides a benchmark for the experimental data analysis. The measurement of the beam spin asymmetry for the scalar meson production may also provide a unique opportunity not only to explore the imaginary part of the hadronic amplitude in the general formulation but also to examine the significance of the chiral-odd generalized parton distribution (GPD) contribution in the leading-twist GPD formulation.