2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/182773We study the single spin asymmetry (SSA) for the pion production with large transverse momentum p_T in semi-inclusive deep inelastic scattering $ep^\uparrow\to eπX$. 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 A_N in $p^\uparrow p\toπX$ collision.19 pages in LaTex. Some discussions added. To appear in Nucl. Phys. BHigh Energy Physics - Phenomenologytext