Target mass and finite momentum transfer corrections to unpolarized and polarized diffractive scatterin

A quantum field theoretic treatment of inclusive deep--inelastic diffractive scattering is given. The process can be described in the general framework of non--forward scattering processes using the light--cone expansion in the generalized Bjorken region. Target mass and finite $t$ corrections of the diffractive hadronic tensor are derived at the level of the twist--2 contributions both for the unpolarized and the polarized case. They modify the expressions contributing in the limit $t, M^2 \to 0$ for larger values of $\beta$ or/and $t$ in the region of low $Q^2$. The different diffractive structure functions are expressed through integrals over the relative momentum of non--perturbative $t$--dependent 2--particle distribution functions. In the limit $t, M^2 \to 0$ these distribution functions are the diffractive parton distribution. Relations between the different diffractive structure functions are derived.