The structure of the nucleons and of the nuclei was actively studied during the twentiethcentury through electron elastic scattering (measuring the electromagnetic formfactors) and deep inelastic electron scattering (measuring the parton distributions). Theformalism of generalized parton distributions (GPD) achieved the unification of the formfactors and the parton distributions. This link gives a source of information about partondynamics, such as the distribution of nuclear forces and orbital momentum insidehadrons. The easiest experimental access to the GPD is the deeply virtual Comptonscattering (DVCS), which corresponds to the hard electroproduction of a real photon.While several experiments focussed on DVCS off the nucleon, only a few experimentsstudied DVCS off a nuclear target. This thesis is dealing with the study of the coherentchannel of DVCS off helium 4, with the aim to extract the real and imaginary parts ofthe Compton form factor thanks to the beam spin asymetry.
