Role of pion pole in hard exlusive meson leptoproduction

We consider the pion pole contribution and transversity effects determined by the $H_T$ and ${\bar{E}}_T$ Generalized Parton Distributions (GPDs) which are essential in hard pseudoscalar and vector meson leptoproduction. We investigate spin effects in the $\omega$ and ${\rho }^0$ reactions. It is shown that the pion pole contribution is very important in the $\omega$ production. Such effects in the ${\rho }^0$ channel are much smaller. Our results on spin asymmetries and spin density matrix elements in these reactions were found to be in good agreement with HERMES data.