Measurements of the Reactionγp→ϕpwith Unpolarized Bremsstrahlung

We have measured the differential photoproduction cross section $\frac{d\sigma }{\mathrm{dt}}$ for the production of $\varphi$ mesons as a function of $t$ at a photon energy of 12 GeV from $\mathrm{}\left|t\right|=0.2\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$ to $\mathrm{}\left|t\right|=1.0\mathrm{}$ ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, and as a function of photon energy from 6 to 19 GeV at a $\mathrm{}\left|t\right|\mathrm{}$ of 0.6 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$. Our results, and all other world data, fall on a universal curve. The slope of the Pomeranchukon trajectory deduced from this experiment is ${\alpha }^{\prime }=-0.03\mathrm{}\pm 0.13$.