K.H. Mütter

Non-singlet axial vector couplings of the baryon octet in lattice QCD*

We calculate in the quenched approximation the F and D parameters characterising the axial vector matrix elements of the baryon octet. The use of an improved fermion action and smeared interpolating fields enables us to go down in quark mass to the SU ( 3 ) symmetric point. Both the F/D ratio and g A are in good agreement with the experimental values within a statistical error of a≈10%.

Determination of the correlation length by varying the boundary conditions in lattice gauge theories

Abstract By Monte Carlo techniques we study the response of the expectation values of Wilson loops (sampled from the interior of a lattice) to the change of boundary conditions. In the case of the pure SU(2) gauge theory, we find, within reasonable computer time, a clear numerical signal for the correlation between the boundary and the interior plaquettes over a distance of up to four lattice spacings. As a result of our computations on 8 4 and 10 4 lattices, we verify the asymptotic freedom behaviour of the correlation length for β values up to 2.3–2.4 and estimate the glueball mass to be m g =(2.35±0.30)√ σ .

Large distance propagators for hadrons on a 56 × 163 lattice

Abstract We have computed hadron propagators in the quenched approximation to Wilson fermions at β = 6 on 24 SU(3) background fields of size 56 × 16 3 . The inversion of the fermion matrix was achieved by the approximate block diagonalization method. We find a clean exponential decay of the ϱ, N and Δ propagators for time separations 8 ≲ t ⩽ 54 at quark masses am q = 0.04 and beyond.

Block diagonalization — An efficient method to compute hadrons on large lattices☆

Abstract We compute hadron masses from Wilson fermions in the quenched approximation. By use of our recently proposed block diagonalization method we are able to extend lattice sizes from (previously) 103 × 20 to 163 × 28, using a CYBER 205 with small memory. First results, based on 360 quark propagators, look very encouraging for our method: very close to κcritical, we achieve good stability of the conjugate gradient algorithm, so that errors can be kept small. We thus can compute quark propagators down to a pion mass of amπ = 0.2. The resulting hadron masses at β = 6 match with the values obtained previously by Lipps et al. on a 103 × 20 lattice. We find a(β = 6) = 0.093 fm and mproton/mp = 1.853(88).

Glueball mass from variant actions in lattice Monte Carlo simulations

Abstract We have measured the mass gap in pure SU(2) gauge theory with Mantons action by means of our previously proposed long distance correlation method. Asymptotic freedom is verified over the β-range 1.3 ⩽ β ⩽ 1.8. The ratio between the lowest glueball mass and the square root of the string tension extracted from lattice calculations is shown to be universal, i.e. it is the same for Mantons and Wilsons action.

Exploring hadron masses in lattice QCD with light quarks and an improved fermion action

Hadron masses are computed using quenched Wilson fermions on gauge configurations obtained after blocking 243×48 lattices twice with the √3 block transformation. An improved Wilson fermion action, motivated by a truncated renormalisation group analysis within the block-diagonalisation scheme, is used. We present results obtained close to the chiral limit, i.e. in the range 0.4 <mτ/mρ<0.85. Moreover, we study finite size effects by combining results obtained with periodic and antiperiodic boundary conditions.

Correlation length for SU(3) guage theory on an 84 lattice

Abstract We compute the correlation length for the pure SU(3) lattice gauge theory by the long distance correlation method. We observe a scaling window, 4.7 ≲ β ≲ 5.6, and deduce a mass gap m g = 320 Λ ± 15%.

Hadron mass computations on a 163 · 28 lattice -a comparison between blocked and unblocked computations

Abstract The hadron spectrum is computed with Wilson fermions on a 16 3 ·28 lattice at β =6.0. A comparison is made with an earlier calculation that uses the block-diagonalisation approximation. The resulting mass ratios from the two calculations are in agreement with each other. The ratio r = a b / a of the lattice spacings of the twice-blocked and unblocked lattices turns out to be 25% below the naive expectation, r =4.

SU(2) mass gap calculation on a 164 lattive

Abstract We compute the mass gap mg with our long-distance correlation method for the SU(2) gauge theory on a 164 lattice by Monte-Carlo methods. The new data are in agreement with asymptotic scaling within 10%.

Testing lattice universality: A comment on the large N approximation of the asymptotic freedom scale parameter Λ

Abstract We check the hypothesis of lattice universality recently put forward by Makeenko, Polikarpov and Zhelokin using our Monte Carlo data for the mean plaquette, the mean plaquette squared and the mass gap in a lattice gauge theory with mixed fundamental adjoint action.