  Forward Drell-Yan process at the LHC is a sensitive tool for investigating
higher twist effects in QCD. The expansion of all Drell-Yan structure functions
is performed assuming GBW saturation model and the saturation scale plays the
role of the hadronic scale of OPE. We show that the Lam-Tung relation is broken
at twist 4. The results open the way for a forthcoming analysis of multiple
scattering and higher twist effects.
