Diffractive Vector Meson Photoproduction from Dual String Theory

Abstract

We study diffractive vector meson photoproduction using string theory via AdS/CFT. The large $s$ behavior of the cross sections for the scattering of the vector meson $V$ on a proton is dominated by the soft Pomeron, ${\sigma }_V\sim s^{2\epsilon -2{\alpha }_P^{\prime }/B}$, where from the string theory model of \cite{nastase2}, $\epsilon$ is approximately 1/7 below 10 GeV, and 1/11 for higher, but still sub-Froissart, energies. This is due to the production of black holes in the dual gravity. In $\varphi$-photoproduction the mesonic Regge poles do not contribute, so that we deal with a pure Pomeron contribution. This allows for an experimental test. At the gauge theory "Planck scale" of about 1-2 GeV, the ratios of the soft Pomeron contributions to the photoproduction cross-sections of different vector mesons involve not only the obvious quark model factors, but also the Boltzmann factors $e^{-4M_V/T_0}$, with $T_0$ the temperature of the dual black hole. The presence of these factors is confirmed in the experimental data for $\rho ,\omega ,\varphi ,J/\psi ,$ and $\psi (2S)$ photoproduction and is compatible with the meager ${\rm Y}$ photoproduction data. Throughout, we use vector meson dominance, and from the data we obtain $T_0$ of about $1.3GeV$, i.e. the gauge theory "Planck scale," as expected. The ratio of the experimental soft Pomeron onset scale ${\hat{E}}_R\sim 9$ GeV and of the gauge theory Planck scale, $T_0\sim 1.3$ GeV conforms to the theoretical prediction of $N_c^2/N_c^{1/4}$.

17 pages, 1 figure, latex

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