Forschungsgruppe FOR 2926/2
Next Generation Perturbative QCD for Hadron Structure:
Preparing for the Electron-Ion Collider
The parton content of nucleons and knowledge on fragmentation of final state partons are key ingredients in precision predictions at today´s particle colliders. In the standard factorization approach to QCD, they provide the essential information on the long-distance parton dynamics, which is inaccessible to perturbative computations.
A central task for modern QCD theory consists of providing precision extractions of these long-
distance parts (typically, parton distributions and fragmentation functions) from comparisons of experimental
data with the corresponding theoretical calculations of the short-distance factors (typically, partonic cross
sections) at high orders of perturbation theory. The typical accuracy of those theoretical predictions is currently
at next-to-next-to-leading order (N2LO) in QCD for most cross sections of interest and even higher for fully
inclusive observables. Motivated by the theoretical progress and the available data from deep-inelastic scattering
and the LHC and the prospects of the future EIC, project P2 presents a unified approach to deliver information
on the non-perturbative parton dynamics at a new level of precision. To that end, it combines all efforts
concerning momentum distributions of partons in the proton as well as lighter and heavier nuclei, addresses
scattering processes with and without polarization, targets fragmentation functions and aims at pushing the
accuracy beyond N2LO in QCD. As such, the project has numerous interrelations to all other projects, either
by exploiting new results to be derived or by sharing ingredients.
The project aims at precise determinations of PDFs in the proton and in nucleons and FFs for identified hadrons in final states with an eye towards the future EIC. For the second funding period, it will be organized in three parts that address PDF and FF fits at N3LO accuracy (project P2a), the analysis of polarized PDFs (project P2b) and the extraction of nuclear PDFs (project P2c). The outcomes of this project will be relevant especially for projects P4 and P5 of the research unit.