Partonic angular momentum and the Sivers asymmetry

We assume a connection between the forward limit of the GPD E and the first moment of the Sivers transverse-momentum distribution, inspired by Burkardt's idea of chromodynamic lensing. Then, we show that it is possible to fit at the same time the values of the nucleon anomalous magnetic moments and the data for semi-inclusive single-spin asymmetries originating from the Sivers effect. This opens a plausible way to quantifying the contribution of the partonic angular momentum to the spin of the nucleon, according to Ji's definition.