Photoproduction of Baryon-Antibaryon Pairs at GlueX

The mechanism of baryon-antibaryon photoproduction has not been extensively studied. Little is known about the dominant exchanges in the $t$-channel or the nature of baryon-like exchanges in the $u$- channel. At GlueX, we are studying the reactions $\gamma p \to \mathcal{\overline{B}B}$$p$, where $\mathcal{\overline{B}B}$ includes $\overline{p}p$ and $\overline{\Lambda}\Lambda$ (with $\Lambda \to \pi^- p, \overline{\Lambda} \to \pi^+ \overline{p}$). Data have been obtained from the respective reaction thresholds up to a beam energy of about 11 GeV. The reactions are also being studied with linearly polarized photons in the energy range between 8.4 and 9 GeV. Kinematic fitting is used for clean extraction of 3 and 5 body final states, respectively. Preliminary spectra from Spring 2016 data will be presented for the angular correlations among the produced particles and for some spin observables including the beam asymmetry $\Sigma$. We expect these measurements to allow identification of the dominant reaction mechanisms at GlueX energies.