Anomalous dimensions of transverse-momentum dependent parton distribution functionsAnomalous dimensions of transverse-momentum dependent parton distribution functions
Faculty of Sciences. Physics
(2008), p. 1-7
We discuss recent developments in the understanding of gauge-invariant transverse-momentum dependent (TMD) parton-distribution functions (PDF). We compute the leading-order MS¯¯¯¯¯-scheme anomalous dimension of such a quantity in the light-cone gauge and show that it receives a contribution that can be associated with a cusp obstruction at transverse light-cone infinity. This anomalous dimension is intimately related to expectation values composed of fields and eikonal factors along a cusped contour and is absent in covariant gauges. The implications of these findings are addressed and a modified definition of TMD PDFs is proposed.