Theory of deeply virtual Compton scattering off the unpolarized proton

Using the helicity amplitudes formalism, we study deeply virtual exclusive electron photoproduction off an unpolarized nucleon target, $ep\ensuremath{\rightarrow}{e}^{\ensuremath{'}}{p}^{\ensuremath{'}}\ensuremath{\gamma}$, through a range of kinematics both in fixed target setting with initial energies 6, 11, and 24 GeV for ion collider. We reformulate cross section bringing to forefront defining features $ep\ensuremath{\rightarrow}{e}^{\ensuremath{'}}{p}^{\ensuremath{'}}\ensuremath{\gamma}$ process, where observables are expressed as bilinear products independent which completely describe it terms electric, magnetic, axial currents nucleon. These contributions checked against Fourier harmonics-based formalism has provided so far underlying mathematical framework Compton scattering (DVCS) related experiments. theoretical model calculations twist-two generalized parton distributions, $H$, $E$, $\stackrel{\texttildelow{}}{H}$, $\stackrel{\texttildelow{}}{E}$, uncover large discrepancies between harmonic series our proposed framework. Most importantly, these numerical differences appear intermediate ${Q}^{2}$ represents sweet spot extracting distributions from data. provide that is ideal, on one side, compare different conventions can be used leading order contribution DVCS QCD, while other facilitates quantitative extraction physically meaningful information experiment traceable controllable approximations region.