We report the first large-acceptance measurement of the beam–spin asymmetry for deuteron photodisintegration (ȳd → pn) in the photon energy range 420 < E<sub>γ</sub> < 620 MeV. The measurement provides important new constraints on the mechanisms of photodisintegration above the Δ resonance and on the photocoupling of the recently discovered d<sup>∗</sup>(2380) hexaquark....