Measurement of the Photon Beam Asymmetry in ${\vec{\hat{I}}}^{3}p\to K^{+}\hat{I}{\pounds }^0$ at $E_{\hat{I}}^3=8.5$ GeV

Abstract

We report measurements of the photon beam asymmetry $\hat{I}\pounds$ for the reaction ${\vec{\hat{I}}}^{3}p\to K^{+}\hat{I}{\pounds }^0$(1193) using the GlueX spectrometer in Hall D at Jefferson Lab. Data were collected 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 $\hat{I}\pounds$ was measured as a function of the Mandelstam variable $t$, and a single value of $\hat{I}\pounds$ was extracted for events produced in the $u$-channel. These are the first exclusive measurements of the photon beam asymmetry $\hat{I}\pounds$ for the reaction in this energy range. For the $t$-channel, the measured beam asymmetry is close to unity over the $t$-range studied, $-t=(0.1-1.4)$(GeV/$c$)${}^2$, with an average value of $\hat{I}\pounds =1.00\pm 0.05$. This agrees with theoretical models that describe the reaction via the natural-parity exchange of the $K^{\ast }$(892) Regge trajectory. A value of $\hat{I}\pounds =0.41\pm 0.09$ is obtained for the $u$-channel integrated up to $-u=2.0$~(GeV/$c$)${}^2$.