Production of Single Negative Pions from Deuterium with Polarized Photons

Abstract

The asymmetry $A=\frac{(d{\ensuremath{\sigma}}_{\ensuremath{\perp}}\ensuremath{-}d{\ensuremath{\sigma}}_{\ensuremath{\parallel}})}{(d{\ensuremath{\sigma}}_{\ensuremath{\perp}}+d{\ensuremath{\sigma}}_{\ensuremath{\parallel}})}$ of the differential cross section for the reaction $\ensuremath{\gamma}d\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}\mathrm{pp}$ has been studied with linearly polarized photons of 3.0 GeV at squared four-momentum-transfers between 0.15 and 2.0 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$. The asymmetry was found to be positive at $\ensuremath{-}t$ values below 0.3 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, dipping to negative values between 0.4 and 0.6 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$, and then rising again to positive values above 0.7 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^{2}$.