Project description

This project aims at elevating the precision of the perturbative input in the QCD calculations of benchmark "hard" processes by one quantum loop to ensure that the theoretical predictions match the accuracy expected from the experimental facilities of the next generation. This includes the computation of the two-loop coefficient functions for generic two-photon processes, QCD splitting functions and evolution kernels up to four loops and three loops for the forward and non-forward (generalized) parton distributions, respectively, and four-loop fragmentation functions. In addition, the matching relations to lattice renormalization schemes will be provided with similar precision.

We plan to continue the computations of anomalous dimensions and coefficient functions in collinear forward and off-forward kinematics at the three- and four-loop level, respectively, with the general aim to control QCD parton evolution at the one percent level. The work program detailed below presents a direct continuation of the studies in the first funding period and remains organized in the three parts that address the collinear evolution with splitting functions and related hard scattering CFs to N 3 LO (project P1a), the evolution equations for GPDs and CFs for DVCS to NNLO (project P1b), and the computation of the necessary conversion factors for lattice renormalization schemes (project P1c). The results will be applied in projects P2 and P3 as the basis for a new generation of high-precision data analyses as well as for studies of power corrections and higher-twist effects.