Connection between the Sivers function and the anomalous magnetic moment

The same light-front wave functions of the proton are involved in both the anomalous magnetic moment of the nucleon and the Sivers function. Using the diquark model, we derive a simple relation between the anomalous magnetic moment and the Sivers function, which should hold in general with good approximation. This relation can be used to provide constraints on the Sivers single spin asymmetries from the data on anomalous magnetic moments. Moreover, the relation can be viewed as a direct connection between the quark orbital angular momentum and the Sivers function.

Figure 1

Diagram to calculate the Sivers function. The arrows $\uparrow /\downarrow$ show the polarizations of the nucleon.

Figure 2

Diagram to calculate the Pauli form factor (or anomalous magnetic moment). The arrows $\uparrow /\downarrow$ show the polarizations of the nucleon.