Production of Single Negative Pions from Deuterium with Polarized Photons

Abstract

The asymmetry $A=\frac{(d{\sigma }_{\perp }-d{\sigma }_{\parallel })}{(d{\sigma }_{\perp }+d{\sigma }_{\parallel })}$ of the differential cross section for the reaction $\gamma d\to {\pi }^{-}\mathrm{pp}$ 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 $-t$ 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 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$.