Speaker
Description
Generalized parton distributions describe the non-forward matrix elements of QCD light-ray operators between hadronic states and unify the concepts of parton densities and hadron form factors. The concept can be extended to transitions between states with different hadronic composition, including multi-hadron states and resonances. These "transition GPDs" offer new opportunities for exploring the QCD structure of hadron resonances and have emerged as a field of study in its own right, with many recent results. This overview covers the concepts, methods, applications, and possible measurements. This includes: (a) Baryon transition GPDs $N \rightarrow \Delta$ and $N \rightarrow N^*$ from theoretical analysis ($1/N_c$ expansion of QCD) and DVCS experiments; (b) Transition matrix elements of QCD energy-momentum tensor and mechanical properties of baryon resonances; (c) Chiral-odd transition GPDs and exclusive pion/kaon electroproduction processes; (d) Near-threshold $N \rightarrow \pi N$ transition GPDs and chiral dynamics; (e) Hard exclusive processes and partonic operators as a new tool for hadron spectroscopy; (f) Prospects for experiments at JLab 12 GeV and EIC (far-forward detectors).
