Single transverse spin asymmetry for large-image pion production in semi-inclusive deep inelastic scattering Original Research Article

We study the single spin asymmetry (SSA) for the pion production with large transverse momentum image in semi-inclusive deep inelastic scattering image. We derive the twist-3 cross section formula for SSA, focussing on the soft-gluon-pole contributions associated with the twist-3 distribution for the nucleon and with the twist-3 fragmentation function for the pion. We present a simple estimate of the asymmetries due to each twist-3 effect from nucleon and pion, respectively, by fixing the overall strength of the relevant nonperturbative quantities by the data on the SSA image in image collision.