Forschungsgruppe FOR 2926/2
Next Generation Perturbative QCD for Hadron Structure:
Preparing for the Electron-Ion Collider
This project is devoted to the study of contributions to scattering processes that are formally of subleading
power in the hard scale. The importance of going beyond the leading power accuracy is widely recognized. One
reason is that such contributions constrain the ultimate accuracy of QCD description based on leading-power
(leading-twist) factorization theorems. They need to be understood for the theory to match the very high data
accuracy expected at the experimental facilities of the next generation. This concerns especially exclusive and
semi-inclusive reactions at the heart of the physics programs of the EIC and JLAB12, where the bulk of data is
and will be concentrated at moderate momentum transfers. Another reason is that higher-twist contributions
actually become unsuppressed in certain regions of phase space. A prime example is provided by multiparton
scattering processes in hadron-hadron collisions. As their importance grows with the collision energy, they are
of considerable interest at the LHC (and even more so at possible future hadron colliders).
We continue the study of power suppressed contributions to hard reactions along the lines outlined in the original proposal. The main difference is that the subproject P3b is not renewed: the research on power corrections in the TMD factorization framework will be continued with minimal DFG support (Mercator Fellowship for Dr. Vladimirov, who is moving from Regensburg to Madrid). The subproject P3c is, on the contrary, considerably extended by adding a broad study program of twist-three GPDs. The general direction will be a transition from formal developments to applications and impact studies.