Nonperturbative QCD contribution to gluon-gluon-eta' vertex
  We investigate the momentum dependence of the g*-g-eta' vertex form factor in the presence of the nonperturbative QCD vacuum condensate. The behaviour of this form factor is crucial for, among other things, some proposed mechanisms devised to explain the large branching ratio for fast eta' production in charmless B decays observed by CLEO. We show that the leading momentum dependence of this vertex form factor is not altered when the contribution of nonperturbative quark condensate is considered. 
Mohammad R. Ahmady (RIKEN), Victor Elias (Western Ontario) and Emi Kou   (Ochanomizu)