Measurement of the photon beam asymmetry in γ⃗p→K+Σ0 at Eγ = 8.5 GeV

We report measurements of the photon beam asymmetry \ud Σ\ud for the reaction \ud γ⃗p→K+Σ0\ud (1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected by using a linearly polarized photon beam in the energy range of 8.2–8.8 GeV incident on a liquid hydrogen target. The beam asymmetry \ud Σ\ud was measured as a function of the Mandelstam variable \ud t\ud , and a single value of \ud Σ\ud was extracted for events produced in the \ud u\ud channel. These are the first exclusive measurements of the photon beam asymmetry \ud Σ\ud for the reaction in this energy range. For the \ud t\ud channel, the measured beam asymmetry is close to unity over the \ud t\ud range studied, \ud −\ud t\ud =\ud (\ud 0.1\ud –\ud 1.4\ud )\ud (\ud GeV\ud /\ud c\ud )\ud 2\ud , with an average value of \ud Σ\ud =\ud 1.00\ud ±\ud 0.05\ud . This agrees with theoretical models that describe the reaction via the natural-parity exchange of the \ud K\ud ∗\ud (892) Regge trajectory. A value of \ud Σ\ud =\ud 0.41\ud ±\ud 0.09\ud is obtained for the \ud u\ud channel integrated up to \ud −\ud u\ud =\ud 2.0\ud (\ud GeV\ud /\ud c\ud )\ud 2\ud .