Espalhamento compton profundamente virtual em colisões elétron-próton e elétron-núcleo

Abstract

The regime of high energies (small x) of the quantum chromodynamics (QCD) has been intensively investigated in experiments at high collision energies. In this regime it is expected that nonlinear effects determine the dynamic behavior of quarks and gluons inside the hadrons. As a consequence of the nonlinear dynamics, it is expected that the growth of the distribution of partons saturate. The description of the saturation regime is given by the Color Glass Condensate (CGC), which is an effective theory which describes the QCD at high energies. In particular, it is conjectured that the nuclear medium amplify the effects of saturation, rendering the distinction between the linear and nonlinear regimes clearer. The saturation plays a key role in diffractive deep inelastic scattering, given the strong dependence of this process in the gluon distribution. As an example of an exclusive diffractive process, we have the deeply virtual Compton scattering (DVCS). This process was studied in the electron-proton scattering at the HERA collider, and because of the clear experimental signature of exclusive processes, it should also be an important observable to prove the saturation in future electron-ion colliders. In order to prove the importance of the saturation effects in the high energy physics, in this work we calculate the DVCS cross section in ep and eA processes using different models based on the CGC. In the electron-proton case, our results describe the current HERA data to the cross section. In the nuclear case, we present predictions for the total cross sections and differential momentum transferred distributions for coherent and incoherent interactions in the kinematical range which will be probed by the future eRHIC and e LHeC colliders. Our results indicate that the predictions for DVCS are strongly dependent on the model used to describe the dipole-hadron interaction, mainly in the region of transition between the linear and nonlinear regimes. Our results also indicate that the analysis of the transferred momentum distribution will allow to separate the coherent and incoherent processes, being the ratio between these processes strongly dependent on the photon virtuality and the atomic number.