Determination of the Beam-Spin Asymmetry of Deuteron Photodisintegration in the Energy Region $E_\gamma=1.1-2.3$ GeV

TL;DR

This study measures the beam-spin asymmetry in deuteron photodisintegration across a broad energy range, providing new data at various angles to improve understanding of the underlying QCD mechanisms.

Contribution

First measurements of beam-spin asymmetries at energies above 1.6 GeV and at angles other than 90°, aiding the development of QCD-based models.

Findings

First data at $ heta_{c.m.}=90^\u00b0$ for energies >1.6 GeV

Angular and energy dependence of $mbda$ characterized

Data will inform models bridging hadronic and partonic physics

Abstract

The beam-spin asymmetry, $\Sigma$, for the reaction $\gamma d\rightarrow pn$ has been measured using the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility (JLab) for six photon-energy bins between 1.1 and 2.3 GeV, and proton angles in the center-of-mass frame, $\theta_{c.m.}$, between $25^\circ$ and $160^\circ$. These are the first measurements of beam-spin asymmetries at $\theta_{c.m.}=90^\circ$ for photon-beam energies above 1.6 GeV, and the first measurements for angles other than $\theta_{c.m.}=90^\circ$. The angular and energy dependence of $\Sigma$ is expected to aid in the development of QCD-based models to understand the mechanisms of deuteron photodisintegration in the transition region between hadronic and partonic degrees of freedom, where both effective field theories and perturbative QCD cannot make reliable predictions.