Speaker
Description
Generalized parton distributions (GPDs) are off-forward matrix elements of quark and gluon operators that enclose information on the total angular momentum of partons, and so on the spin of hadrons (cf. EMC measurements and spin puzzle). In addition, GPDs enable tomography of the nucleon allowing to study spatial distribution of partons as a function of their momentum. To access GPDs one needs to consider exclusive processes, such as deeply virtual and timelike Compton scattering (DVCS and TCS). At LO these processes are mainly sensitive to GPDs in a restricted kinematic domain, this is $x = \xi$, where $x$ represents the average fraction of longitudinal momentum carried by an active parton, while $\xi$ is the so-called skewness variable. The process that avoids this constraint is double deeply virtual Compton scattering (DDVCS) for which an electron scatters off a nucleon and produces a lepton pair. The extra virtuality with respect to DVCS and TCS allows for LO access to GPDs at $x\neq\xi$.
In this talk, the importance of DDVCS for GPD physics, key objects for the understanding of the hadron's spin, will be highlighted. Elements of impact studies for current and future experiments at facilities such that the Electron-Ion Collider (EIC) and JLab have been worked out by means of the PARTONS software and the EpIC Monte Carlo event generator. For this purpose, a new formulation of DDVCS based on the spinor techniques by R. Kleiss and W. J. Stirling (1980s) was developed and will be shown as well.
