A lattice study of the masses of singlet 0++ mesons
  We compute the masses of the flavour singlet 0++ mesons using (n_f=2) unquenched lattice QCD with the Iwasaki and Wilson gauge actions. Both fermionic and glueball interpolating operators are used to create the states. The mass of the lightest 0++ meson is suppressed relative to the mass of the 0++ glueball in quenched QCD at an equivalent lattice spacing. We discuss two possible physical reasons for this. 
UKQCD Collaboration: A. Hart, C. McNeile, C. Michael, and J.   Pickavance