Project: TMDs -- Scale dependence of TMDs

Prace Call: 17th
ID: 2018184451, Leader: Andreas Schaefer
Affiliation: Regensburg University, DE
Research Field: Fundamental Constituents of Matter
Collaborators: Michael Engelhardt New Mexico State University USA , Jeremy Green Deutsches Elektronen-Synchrotron DE , Rajan Gupta Los Alamos National Laboratory USA , Piotr Korcyl Jagiellonian university PL , Andreas Rabenstein Regensburg University DE , Maximillian Schlemmer Regensburg University DE , Christian Zimmermann Regensburg University DE , Alexey Vladimirov Regensburg University DE
Resource Awarded: 44 Mil. core hours on SuperMUC


This project is part of a major German-US lattice effort to investigate the properties of Transverse Momentum Dependent parton distribution functions (TMDs). The experimental investigation of TMDs is one of the main physics goals of the projected new US accelerator EIC (Electron Ion Collider) the construction of which is pursued jointly by the Brookhaven National Laboratory (BNL) and the Thomas Jefferson National Accelerator Facility. The emphasis on TMDs is motivated by the fact that they link experimental observables to the detailed properties of QCD gauge links and thus to the most characteristic features of QCD. The physics of TMDs is still only partly understood. The open problem which is phenomenologically most relevant is the scale dependence which, in contrast to the case of normal parton distribution functions, has unsuppressed non-perturbative contributions. The aim of the present project is, therefore, to study the scaling of TMDs on the lattice. To do so we want to use the large number of ensembles which were generated by the CLS collaboration, precisely with the aim to study the dependence on the lattice constant a. For these ensembles, open boundary conditions were used, which avoid the problem of diverging topological autocorrelation times for small a. Settling the non-perturbative scaling properties of TMDs would mark a major advance in our understanding of hadron structure.