High-Energy Photomeson Production from Hydrogen Via the "uChannel"

We have investigated the photoproduction process $\gamma +p\to {\pi }^{+}+n$ over a wide range of energies and $u$ values at the Stanford Linear Accelerator Center (SLAC) accelerator. We also have investigated $\gamma +p\to {\pi }^{-}+N^{*++}$ at one value of $u$ and $\gamma +p\to K^{+}+{\Lambda }^0$, ${\Sigma }^0$ at one $u$ value and three energies. Our results for $\frac{d\sigma }{\mathrm{du}}$ for the photoproduction of ${\pi }^{+}$ mesons from hydrogen are roughly $\frac{\alpha }{2\pi }$ of the corresponding cross sections for the elastic scattering of ${\pi }^{-}$ mesons from hydrogen. The $u$ dependence of our cross sections is not dominated by nucleon exchange as it is in the case of ${\pi }^{+}p$ elastic scattering.