Transverse spin effects and higher twist in the singlet channel

Abstract

The effects, originating from the longitudinal gluon polarization, are considered. We derive the analogue of the Wandzura-Wilczek relation for the light-cone distributions of polarized gluons in a transversely polarized nucleon. The short distance cross-section is entirely due to the intrinsic transverse momenta of gluon in the nucleon, in complete analogy to the quark case. Numerical estimate for the double spin transverse asymmetries are presented. The distribution of longitudinal gluons in a nucleon, introduced earlier by Gorsky and Ioffe, is estimated from below by making use of the positivity of density matrix. The similar upper bound for the nonperturbative polarized charm is discussed.