$\gamma \to \rho^0$ impact factor in QCD: light-cone sum rule calculation

We discuss the $\gamma \to \rho^0$ impact factor, i.e., the transition amplitude of a photon to a neutral vector meson$\rho^0$, where the transition is mediated by the two $t$-channel gluons. The impact factoris a building block in the QCD descriptions of high-energy exclusive processes like $\gamma p \to \rho^0 p$, and $\gamma\gamma \to \rho^0 \rho^0$, in particular, for the forward production of $ \rho^0$. The impact factorfor the longitudinal polarization of the vector mesonobeys the QCD factorization, while the factorization is known to break down for the transverse polarization, indicating that the impact factorfor the transversely polarized vector mesonis dominated by the ``non-factorizable'' soft contributions. We study the $\gamma \to \rho^0$ impact factorconstructing the light-cone QCD sum rulesfor the corresponding amplitudes, which allow us to estimate the relevant soft contributions in a largely model-independent way, with the use of dispersion relations and quark-hadron duality.