Timelike Compton scattering off the proton and generalized parton distributions

We study the exclusive photoproduction of a lepton pair off the proton with the aim of studying the proton quark structure via the Generalized Parton Distributions (GPD) formalism. After deriving the amplitudes of the processes contributing to the gamma P --> P'e(+)e(-), the timelike Compton scattering and the Bethe-Heitler process, we calculate all unpolarized, single- and double- spin beam-target observables in the valence region in terms of GPDs.