Final state interactions and gauge invariant parton distributions

Parton distributions contain factorizable final state interaction effects originating from the fast-moving jet, produced by the highly virtual probe which strikes the active parton in the hadron, interacting with the target spectators. We show that these interactions lead to gauge-invariant transverse momentum-dependent parton distributions in deeply inelastic scattering. As compared to previous analyses, our study demonstrates the existence of extra scaling contributions from transverse components of the gauge potential at the light-cone infinity. They form a transverse gauge link which is indispensable for restoration of the gauge invariance of parton distributions in the light-cone gauge where the potential is nonlocal. Our finding helps to explain a number of features observed in a model calculation of structure functions in the light-cone gauge.