  The observed results for the azimuthal single spin asymmetries (SSAs) of the
proton, measured in the semi-inclusive deep inelastic scattering (SIDIS), can
be explained by the final-state interaction (FSI) from the gluon exchange
between the outgoing quark and the target spectator system. SSAs require a
phase difference between two amplitudes coupling the target with opposite spins
to the same final state. We have used the model of light front wave functions
(LFWFs) consisting of a spin-$\frac{1}{2}$ system as a composite of a
spin-$\frac{1}{2}$ fermion and a spin-1 vector boson to estimate the SSAs. The
implications of such a model have been investigated in detail by considering
different coupling constants. The FSIs also produce a complex phase which can
be included in the LFWFs to calculate the Sivers and Boer-Mulders distribution
functions of the nucleon.
