We perform a lattice mass analysis in the flavour singlet pseudoscalar channel on the SESAM and TXL full QCD vacuum configurations, with 2 active flavours of dynamical Wilson fermions at beta = 5.6. At our inverse lattice spacing, a^-1 = 2.3 GeV, we retrieve by a chiral extrapolation to the physical light quark masses the value m_eta' = 3.7(+8)(-4) m_pi. A crude extrapolation from (N_f = 3) phenomenology would suggest m_eta' \approx 5.1 m_pi for N_f = 2 QCD. we verify that the mass gap between the singlet state eta' and the pi flavour triplt state is due to gauge configurations with non-trivial topology.
Cite
@article{arxiv.hep-lat/0010005,
title = {Flavour singlet pseudoscalar masses in N_f = 2 QCD},
author = {T. Struckmann and K. Schilling and G. Bali and N. Eicker and S. Guesken and Th. Lippert and H. Neff and B. Orth and W. Schroers and J. Viehoff and P. Ueberholz},
journal= {arXiv preprint arXiv:hep-lat/0010005},
year = {2009}
}