A new class of exclusive processes to better measure the x-dependence of DAs and GPDs

We propose a new class of exclusive processes for extracting generalized parton distribution functions (GPDs), which provide a powerful theoretical tool to quantify the spatial distribution of quarks and gluons inside a bound hadron. We argue that these processes can be systematically studied in terms of QCD factorization approach, and demonstrate that these processes offer an enhanced sensitivity to the momentum fraction $x$ of GPDs, for which existinig process, such as DVCS, provides almost no sensitivity. Using the exclusive massive-photon-pair production in meson-baryon collisions, and exclusive massive photon-pion production in photon-baryon collisions, as examples, we show that the leading non-perturbative contribution to these processes can be systematically factorized into pion distribution amplitude (DA) and baryon's GPDs. We demonstrate quantitatively the capability of this new class of exclusive processes to provide an enhanced sensitivity to the momentum fraction $x$-dependence of both DAs and GPDs.