A new twist-3 analysis of the single transverse-spin asymmetry for pion and kaon production at RHIC

We present a new analysis for the single-transverse spin asymmetry (SSA) for the inclusive pion and kaon productions in the proton-proton collisions measured at RHIC. The framework we use is the collinear factorization in which SSA appears as a twist-3 observable resulting from the multiparton correlations in the hadrons. As a relevant multiparton correlation, we include all the contributions associated with the quark-gluon correlation functions in the transversely polarized proton, i.e., those from the soft-gluon-pole (SGP) and the soft-fermion-pole (SFP). We have found that the SGP contribution alone is insufficient to describe the observed RHIC AN data and the inclusion of the SFP contribution plays an important role for the improved description of the data. In particular, PT-dependence of AN and AN for K- have been well described in our new analysis.