Determination of the beam-spin asymmetry of deuteron photodisintegration in the energy region Eγ=1.1 -2.3 GeV

Abstract

© 2015 American Physical Society. The beam-spin asymmetry, Σ, for the reaction γd→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, θc.m., between 25 and 160. These are the first measurements of beam-spin asymmetries at θc.m.=90 for photon-beam energies above 1.6 GeV, and the first measurements for angles other than θc.m.=90. The angular and energy dependence of Σ 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.