Recent progress in the nucleon spin structure functions(Recent Developments in QCD and Hadron Physics)

Abstract

We review the spin-dependent structure functions of the nucleon. From a view point of factorization theorem in QCD, we present systematic treatment of the various parton distribution functions, and discuss their physical relevance. Explicit definitions of relevant twist-2 and twist-3 parton distribiitions are given as nucleon matrix elements of nonlocal light-cone operators, and their renormalization and the Q^2-evolution are briefly mentioned. Unique features of the transversity distribution h_1 and of the "measurable" higher-twist distributions h_L and g_T are emphasized. Based on these developments, we discuss prospects of future experiments which will give us opportunities to obtain new information of quark-gluon structure of the nucleon.