Hard Processes with Spin-Dependent Parton Distributions

Abstract

To test a possible color-octet contribution of heavy quarkonium productions, we propose $ψ$'-productions for small-$p_T$ regions, where the color-singlet $ψ$' state cannot be produced by the gluon-gluon fusion owing to charge conjugation. We also point out that these processes are very useful to deduce informations of spin-dependent gluon distributions $Δg$.