Speaker
Hervé MOUTARDE
Description
In order to learn effectively from measurements of Generalised Parton Distributions (GPDs), it is desirable to compute them using a framework that can potentially connect empirical information with basic features of the Standard Model. We sketch an approach to such computations, based upon a rainbow-ladder (RL) truncation of QCD's Dyson-Schwinger equations and exemplified via the pion's valence dressed-quark GPD. Our analysis focuses primarily on vanishing skewness, although we also capitalise on the symmetry-preserving nature of the RL truncation by connecting the considered pion GPD with the pion's valence-quark parton Distribution Amplitude. We explain that the impulse-approximation used hitherto to define the pion's valence dressed-quark GPD is generally invalid owing to omission of contributions from the gluons which bind dressed-quarks into the pion. A simple correction enables us to identify a practicable improvement to the approximation for the pion GPD at vanishing skewness, expressed as the Radon transform of a single amplitude. Therewith we obtain results for the associated impact-parameter dependent distribution, which provides a qualitatively sound picture of the pion's dressed-quark structure at an hadronic scale. We evolve the distributions to the scale 2\,GeV, so as to facilitate comparisons in future with results from experiment or other nonperturbative methods.
Author
Hervé MOUTARDE
