  We make use of a simple scalar diquark model to study the potential
transverse momentum and potential angular momentum, defined as the difference
between the Jaffe-Manohar and Ji notions of transverse momentum and orbital
angular momentum, respectively. A non-vanishing potential angular momentum has
been previously found in lattice calculations and is believed to appear due to
the effects of initial/final state interactions between the spectator system
and the struck quark in high energy scattering processes. Such re-scattering
phenomena are similar in nature to those who are responsible for generating the
Sivers shift. This motivates us to search for an estimate of the potential
angular momentum in terms of the expectation value of the transverse momentum
of the struck quark.
