Nuclear effects and their interplay in nuclear deeply virtual Compton scattering amplitudes

In this paper we analyze nuclear medium effects on deeply virtual Compton scattering (DVCS) amplitudes in the x_bj range of 10^-1 - 10^-4 for a large range of Q² and four different nuclei. We use our nucleon generalized parton distribution model capable of describing all currently available DVCS data on the proton and extend it to the nuclear case using two competing parametrizations of nuclear effects. The two parametrizations, though giving different absolute numbers, yield the same type and magnitude of effects for the imaginary and real parts of the nuclear DVCS amplitude. The imaginary part shows stronger nuclear shadowing effects compared to the inclusive case, i.e., F₂^N, whereas in the real part nuclear shadowing at small x_bj and antishadowing at large x _bj combine through evolution to yield an even greater suppression than in the imaginary part up to large values of x_bj. This is the first time that such a combination of nuclear effects has been observed in a hadronic amplitude. The experimental implications will be discussed in a subsequent publication.