High Energy Exclusive Leptoproduction of the $\rho$-meson: Theory and Phenomenology.

I. V. Anikin, Adrien Besse, D. Yu. Ivanov, B. Pire, L. Szymanowski & S. Wallon
AWe describe the hard leptoproduction of transversally polarized rho-meson, up to twist~3 accuracy, including 2- and 3- particles Fock-states, in the HERA kinematics of high center-of-mass energy. We first build a model based on a simple approach to the unintegrated gluon density (the parton impact factor) that we compare with H1 and ZEUS data for the ratios of helicity amplitudes $T(\gamma^{*}_T \to \rho_T)/T(\gamma^{*}_L \to \rho_L)$ and $T(\gamma^{*}_T \to \rho_L)/T(\gamma^{*}_L \to \rho_L)$ and get a good...