Deeply virtual Compton scattering on longitudinally polarized protons at CLAS

The Generalized Parton Distributions (GPDs) have emerged as a universal tool to describe hadrons in terms of their elementary constituents, the quarks and the gluons. Deeply Virtual Compton Scattering (DVCS) ($e p \rightarrow e' p' \gamma$) is one of the simplest processes that can be described in terms of GPDs. The DVCS-Bethe-Heitler (BH) interference gives rise to spin asymmetries, which can be connected to combinations of Compton Form Factors (CFFs), which are integrals of GPDs. The longitudinal target single-spin asymmetry (SSA) is directly proportional to the imaginary part of the DVCS amplitude, and gives access to a combination of the CFFs $Im(\tilde {\mathcal{H}})$ and $Im(\mathcal{H})$, whereas the double-spin asymmetry (DSA) is proportional to a combination of the CFFs of $Re(\tilde{\mathcal{H}})$ and $Re(\mathcal{H})$. These asymmetries were measured in a dedicated experiment at Jefferson Lab using the CEBAF 6-GeV polarized-electron beam, a longitudinally polarized solid-state ${}^{14}{\rm NH}_3$ target, and the CEBAF Large Acceptance Spectrometer, together with the Inner Calorimeter. DVCS/BH events were selected over the following kinematic ranges: 1 $< Q^{2} <$ 4.5 GeV${}^{2}$, 0.1 $< x_{B} <$ 0.58, 0.08 $< -t <$ 1.8 GeV${}^{2}$ and, the target-SSA and DSA were