ExclusiveρProduction by Virtual Photons

The cross section for production of ${\rho }^0$ mesons has been measured in the reaction $e+p\to e+p+{\pi }^{+}+{\pi }^{-}$. The cross section is presented as a function of $W$, the c.m. energy of the virtual-photon-proton system, and -$Q^2$, the square of the virtual-photon mass. The vector-dominance model is not able to describe the dependence of the cross section on the parameters $Q^2$ and $W$. The slope parameter $B$ describing the scattering of the proton exhibits a significant variation with $Q^2$.