Search

For lattice QCD with two sea quark flavors we study the static quark-antiquark potential $V(R)$ in the regime where string breaking is expected. In order to increase the statistics, we make full use of the lattice information by including all lattice vectors $\mathbf{R}$ to any given separation $R=|\mathbf{R}|$ in the infrared regime. The corresponding paths between the lattice points are constructed by means of a generalized Bresenham algorithm as known from computer graphics. As a result, we achieve a determination of the Wilson loops in the range $0.8\char21{}1.5 \mathrm{fm}$ with hitherto unknown precision. Finally, we discuss the impact of this approach on the signal of the transition matrix element between two- and four-quark states.

We perform a lattice mass analysis in the flavor singlet pseudoscalar channel on the SESAM and TχL full QCD vacuum configurations, with 2 active flavors of dynamical Wilson fermions at β=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 η ′=3.7 -4 +8 m π . A crude extrapolation from (Nf=3) phenomenology would suggest m η ′≈5.1m π for Nf=2 QCD. We verify that the mass gap between the singlet state η′ and the π flavor triplet state is due to gauge configurations with nontrivial topology.