Deuteron photodisintegration by polarized photons in the region of the $d^{\ast }(2380)$

Abstract

We report the first large-acceptance measurement of the beam-spin asymmetry for deuteron photodisintegration (${\vec{\hat{I}}}^{3}d\to pn$) in the photon energy range $400<E_{\hat{I}}^3<630$~MeV. The measurement provides important new constraints on the mechanisms of photodisintegration above the delta resonance and on the photocoupling of the recently discovered $d^{\ast }(2380)$ hexaquark.