Searcharxiv⌕ Search

arXiv subjects

J. Fingberg

Publications and source records attributed to J. Fingberg.

8 recordsLinked to original sources
arXiv1997

Bottomonium from NRQCD with Dynamical Wilson Fermions

We present results for the b \bar b spectrum obtained using an O(M_bv^6)-correct non-relativistic lattice QCD action. Propagators are evaluated on SESAM's three sets of dynamical gauge configurations generated with two flavours of Wilson fermions at beta = 5.6. Compared to a quenched simulation at equivalent lattice spacing we find better agreement of our dynamical data with experimental results in the spin-independent sector but observe no unquenching effects in hyperfine-splittings. To pin down the systematic errors we have also compared quenched results in different ``tadpole'' schemes and used a lower order action.

hep-lat↗
arXiv1997

Improved Upsilon Spectrum with Dynamical Wilson Fermions

We present results for the b \bar b spectrum obtained using an O(M_bv^6)-correct non-relativistic lattice QCD action, where M_b denotes the bare b-quark mass and v^2 is the mean squared quark velocity. Propagators are evaluated on SESAM's three sets of dynamical gauge configurations generated with two flavours of Wilson fermions at beta = 5.6. These results, the first of their kind obtained with dynamical Wilson fermions, are compared to a quenched analysis at equivalent lattice spacing, beta = 6.0. Using our three sea-quark values we perform the ``chiral'' extrapolation to m_eff = m_s/3, where m_s denotes the strange quark mass. The light quark mass dependence is found to be small in relation to the statistical errors. Comparing the full QCD result to our quenched simulation we find better agreement of our dynamical data with experimental results in the spin-independent sector but observe no unquenching effects in hyperfine-splittings. To pin down the systematic errors we have also compared quenched results in different ``tadpole'' schemes as well as using a lower order action. We find that spin-splittings with an O(M_bv^4) action are O(10%) higher compared to O(M_bv^6) results. Relative to the results obtained with the plaquette method the Landau gauge mean link tadpole scheme raises the spin splittings by about the same margin so that our two improvements are opposite in effect.

hep-lat↗
arXiv1996

Super-heavy Quarkonia as a probe of the QCD Vacuum

We investigate the effect of a non-perturbative gluon condensate on the spectrum of bound states of extremely heavy quarks using Non-Relativistic-QCD (NRQCD). Simulations are done with an improved gluon action on small lattices. We compare our numerical results with perturbative calculations to test the consistency.

hep-lat↗
arXiv1994

Scaling in the Positive Plaquette Model and Universality in SU(2) Lattice Gauge Theory

We investigate universality, scaling, the beta-function and the topological charge in the positive plaquette model for SU(2) lattice gauge theory. Comparing physical quantities, like the critical temperature, the string tension, glueball masses, and their ratios, we explore the effect of a complete suppression of a certain lattice artifact, namely the negative plaquettes, for SU(2) lattice gauge theory. Our result is that this modification does not change the continuum limit, i.e., the universality class. The positive plaquette model and the standard Wilson formulation describe the same physical situation. The approach to the continuum limit given by the beta-function in terms of the bare lattice coupling, however, is rather different: the beta-function of the positive plaquette model does not show a dip like the model with standard Wilson action.

hep-lat↗
arXiv1993

Computation of the Spatial String Tension in High Temperature SU(2) Gauge Theory

A detailed investigation of the temperature dependence of the spatial string tension $σ_s$ in $SU(2)$ gauge theory is presented. A sustained performance of 3~GFLOPS on a 64K Connection Machine CM-2 equivalent has been achieved. Scaling of $σ_s$ between $β=2.5115$ and $β=2.74$, on large lattices, is demonstrated. Below the critical temperature, $T_c$, $σ_s$ remains constant. For temperatures larger than $2T_c$ the temperature dependence can be parametrized by $σ_s(T) = (0.369\pm 0.014)^2 g^4(T)T^2$, where $g(T)$ is a 2-loop running coupling constant with the scale parameter determined as $Λ_T = (0.076\pm 0.013)T_c$.

hep-lat↗
arXiv1993

The Spatial String Tension in the Deconfined Phase of the (3+1)-Dimensional SU(2) Gauge Theory

We present results of a detailed investigation of the temperature dependence of the spatial string tension in SU(2) gauge theory. We show, for the first time, that the spatial string tension is scaling on the lattice and thus is non-vanishing in the continuum limit. It is temperature independent below Tc and rises rapidly above. For temperatures larger than 2Tc we find a scaling behaviour consistent with sigma_s(T) = 0.136(11) g^4(T) T^2, where g(T) is the 2-loop running coupling constant with a scale parameter determined as Lambda_T = 0.076(13) Tc.

hep-lat↗
arXiv1992

Scaling and Asymptotic Scaling in the SU(2) Gauge Theory

We determine the critical couplings for the deconfinement phase transition in $SU(2)$ gauge theory on $N_τ\times N_σ^3$ lattices with $N_τ= 8$ and 16 and $N_σ$ varying between 16 and 48. A comparison with string tension data shows scaling of the ratio $T_c / \sqrtσ$ in the entire coupling regime $β=2.30-2.75$, while the individual quantities still exhibit large scaling violations. We find $T_c / \sqrtσ=0.69(2)$. We also discuss in detail the extrapolation of $T_c / Lambda_{\rm{\bar{M} \bar{S}}}$ and $\sqrtσ / Lambda_{\rm{\bar{M}\bar{S}}}$ to the continuum limit. Our result, which is consistent with the above ratio, is $T_c / Lambda_{\rm{\bar{M}\bar{S}}} = 1.23(11)$ and $\sqrtσ / Lambda_{\rm{\bar{M}\bar{S}}} = 1.79(12)$. We also comment upon corresponding results for $SU(3)$ gauge theory and four flavour QCD.

hep-lat↗