Ratio ofπ−toπ+Photoproduction from Deuterium at 8 and 16 GeV

We have studied the ratio $R=\left[\frac{d\sigma (\gamma d\to {\pi }^{-}pp)}{\mathrm{dt}}\right]{\left[\frac{d\sigma (\gamma d\to {\pi }^{+}nn)}{\mathrm{dt}}\right]}^{-1\mathrm{}}$ at 8 and 16 GeV for momentum transfers $\mathrm{}\left|t\right|\mathrm{}$ from about 0.001 to 1.3 Ge${\mathrm{V}}^2$. $R$ is close to unity for $\mathrm{}\left|t\right|<{m_{\pi }}^2$, but falls very rapidly with increasing $\mathrm{}\left|t\right|\mathrm{}$, passing through ½ near $\mathrm{}\left|t\right|=0.1\mathrm{}$ Ge${\mathrm{V}}^2$ and having a minium value of about $\frac{1}{3}$ near $\mathrm{}\left|t\right|=0.4\mathrm{}$ Ge${\mathrm{V}}^2$; it slowly increases at larger momentum transfers. These results are similar to those obtained in other laboratories at 3.4 and 5 GeV. This implies considerable interference between the isoscalar and isovector photon amplitudes.