Twist-3 effects in polarized Drell-Yan and semi-inclusive DIS

Spin dependent processes in high energy scatterings provide us with a possibility to extract twist-3 distribution and fragmentation functions which represent quark-gluon correlations inside the hadrons. A well known example is the nucleon’s transverse spin-structure function g2(x,Q ). In this report, we discuss two other processes in which twist-3 distribution functions reveal themselves as a leading contribution with respect to the inverse power of the hard momentum Q. The first one is the longitudinal (L) and the transverse (T ) spin asymmetry ALT in the nucleon-nucleon polarized Drell-Yan process. We present a simple estimate for ALT in comparison with ALL and ATT .[ 1] The second one is the semi-inclusive production of a polarized spin-1/2 baryon in the deep inelastic scattering from a polarized nucleon. A formula for the cross section is presented. In LO QCD, the double spin asymmetries in the nucleon-nucleon polarized Drell-Yan process are given by [ 2]