Project description

Heavy quarkonia offer a unique environment to study the interplay of perturbative and nonperturbative QCD phenomena. This developing active field sees rapid progress on both theoretical and experimental sides. The most elaborate theory framework for inclusive quarkonium production is currently given by nonrelativistic QCD (NRQCD). While quarkonium hadroproduction data have become very precise and diverse in the LHC era, the electron-proton collision data from HERA still suffered from restricted statistics and kinematic ranges. This is why the highly anticipated EIC results are going to deliver for electron-proton collisions a revolutionary effect, similar to the one LHC had for hadroproduction observables. But to resolve present data-theory tensions and to keep up with the advance in experimental precision, we also need to extend our theoretical analyses to the next-to-next-to-leading order (NNLO). These NNLO calculations are the content of this project, with the concrete aim of having full NNLO NRQCD predictions for EIC photoproduction by the end of the project, possibly even for DIS. These NNLO calculations are extremely challenging. By implementing the reverse unitarity method, we are also introducing completely new technology in the field of NRQCD calculations.

When this project begins, we will have completed the comparison with our previous NLO calculations. But then the hardest part only starts. We need to implement IBP reduction one perturbative order higher than before and identify and solve all NNLO master integrals. Hereby in particular the double-real master integrals are of a completely new type not found in the literature. Having performed all analytical calculations and having produced running NNLO codes, we can start with our numerical evaluations with the aim of complete NNLO calculations for EIC photoproduction, if time permits even DIS. We go into more details about IBP reduction, the master integral evaluation methods and the numerical evaluation program in the following.