Contribution of the twist-3 fragmentation function to single transverse-spin asymmetry in SIDIS

We study the contribution of the twist-3 fragmentation function to the single transverse-spin asymmetry in SIDIS within the framework of the collinear factorization. Using the Ward-Takahashi identity in QCD, we establish the collinear twist-3 formalism in the Feynman gauge to calculate its non-pole contribution to the asymmetry.