Leptonic Signals from off-shell Z Boson Pairs at Hadron Colliders
  We study the gluon fusion into pairs of off-shell Z bosons and their subsequent decay into charged lepton pairs at hadron colliders. We do not restrict the intermediate state Z bosons to the narrow width approximation but allow for arbitrary invariant masses. We compare the strength of this process with the known leading order results for q q_bar -> Z Z -> 4 l and for g g -> H -> Z Z -> 4 l . 
C.Zecher, T.Matsuura, J.J.van der Bij