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MILC Collaboration

Publications and source records attributed to MILC Collaboration.

29 records · Page 2Linked to original sources
arXiv1999

Heavy-Light Decay Constants with Dynamical Gauge Configurations and Wilson or Improved Valence Quark Action

We describe a calculation of heavy-light decay constants including virtual quark loop effects. We have generated dynamical gauge configurations at three $β$ values using two flavors of Kogut-Susskind quarks with a range of masses. These are analyzed with a Wilson valence quark action. Preliminary results based on a ``fat-link'' clover valence quark action are also reported. Results from the two methods differ by 30 to 50 MeV, which is presumably due to significant - but as yet unobserved - lattice spacing dependence in one or both of the approaches.

hep-lat↗
arXiv1998

Lattice Determination of Heavy-Light Decay Constants

We report on the MILC collaboration's calculation of $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$, and their ratios. Our central values come from the quenched approximation, but the quenching error is estimated from $N_F=2$ dynamical staggered lattices. We use Wilson light valence quarks and Wilson and static heavy quarks. We find, for example, $f_B=157 \pm 11 {}^{+25}_{-9} {}^{+23}_{-0} \MeV$, $f_{B_s}/f_B = 1.11 \pm 0.02 {}^{+0.04}_{-0.03} \pm 0.03$, $f_{D_s} = 210 \pm 9 {}^{+25}_{-9} {}^{+17}_{-1} \MeV$ and $f_{B}/f_{D_s} = 0.75 \pm 0.03 {}^{+0.04}_{-0.02} {}^{+0.08}_{-0.00}$, where the errors are statistical, systematic (within the quenched approximation), and systematic (of quenching), respectively.

hep-ph↗
arXiv1998

Light hadron spectrum with Kogut-Susskind quarks

We made an extensive study of the light hadron spectrum using the Wilson gauge action and Kogut-Susskind quarks. Using both dynamical quarks and the quenched approximation, we determine hadron masses for five and four gauge couplings respectively, with at least five quark masses at each coupling. In the continuum limit, we find a significant difference between two flavors of dynamical quarks and the quenched approximation for a range of quark masses.

hep-lat↗
arXiv1998

Continuum limit of lattice QCD with staggered quarks in the quenched approximation - a critical role for the chiral extrapolation

We calculate the light quark spectrum of lattice QCD in the quenched approximation using Kogut-Susskind quarks. By combining results for different lattice spacings, several volumes and five quark masses, we are able to take the light quark mass, infinite volume, continuum limit. When we use non-linear chiral extrapolations, we find that the nucleon to rho mass ratio is 1.254 +- 0.018 +- 0.027, where the errors are statistical and systematic (within the quenched approximation), respectively. This should be compared with the experimental value of 1.22. Our results indicate that the error due to quenching is less than about 5%.

hep-lat↗
arXiv1998

Tests of Hypercubic Fermion Actions

I have performed scaling tests using quenched spectroscopy of a family of fermion actions which have a hypercubic kinetic term, gauge connections built of smeared links, and an anomalous magnetic moment term. These actions show improved rotational invariance compared to the standard Wilson action and to the tadpole-improved clover action. Hyperfine splittings are improved compared to the standard Wilson action (at the level of a factor of three in the lattice spacing), and are about the same as for the tadpole-improved clover action.

hep-lat↗
arXiv1997

Quenched hadron spectroscopy with improved staggered quark action

We investigate light hadron spectroscopy with an improved quenched staggered quark action. We compare the results obtained with an improved gauge plus an improved quark action, an improved gauge plus standard quark action, and the standard gauge plus standard quark action. Most of the improvement in the spectroscopy results is due to the improved gauge sector. However, the improved quark action substantially reduces violations of Lorentz invariance, as evidenced by the meson dispersion relations.

hep-lat↗
arXiv1997

Light quark spectrum with improved gauge and fermion actions

We report on a study of the light quark spectrum using an improved gauge action and both Kogut-Susskind and Naik quark actions. We have studied six different lattice spacings, corresponding to plaquette couplings ranging from 6.8 to 7.9, with five to six quark masses per coupling. We compare the two quark actions in terms of the spectrum and restoration of flavor symmetry. We also compare these results with those from the conventional action.

hep-lat↗
arXiv1997

Light hadron spectrum---MILC results with the Kogut-Susskind and Wilson actions

We present the current status of our ongoing calculations of the light hadron spectrum with both Kogut-Susskind (KS) and Wilson quarks in the valence or quenched approximation. We discuss KS quarks first and find that the chiral extrapolation is potentially the biggest source of systematic error. For the Wilson case, we focus on finite volume and source size effects at 6/g^2=5.7. We find no evidence to support the claim that there is a finite volume effect between N_s=16 and 24 of approximately 5%.

hep-lat↗
arXiv1997

Heavy-light decay constants---MILC results with the Wilson action

We present the current status of our ongoing calculations of pseudoscalar meson decay constants for mesons that contain one light and one heavy quark (f_B, f_{B_s}, f_D, f_{D_s}). We are currently generating new gauge configurations that include dynamical quarks and calculating the decay constants. In addition, we have several new results for the static approximation. Those results, as well as several refinements to the analysis, are new since Lattice '96. Our current (still preliminary) value for f_B is 156 +- 11 +- 30 +- 14 MeV, where the first error is from statistical and fitting errors, the second error is an estimate of other systematic errors within the quenched approximation and the third error is an estimate of the quenching error. For the ratio f_{B_s}/f_B, we get 1.11 +- 0.02 +- 0.03 +- 0.07.

hep-lat↗
arXiv1997

QCD Thermodynamics with an Improved Lattice Action

We have investigated QCD with two flavors of degenerate fermions using a Symanzik-improved lattice action for both the gauge and fermion actions. Our study focuses on the deconfinement transition on an $N_t=4$ lattice. Having located the thermal transition, we performed zero temperature simulations nearby in order to compute hadronic masses and the static quark potential. We find that the present action reduces lattice artifacts present in thermodynamics with the standard Wilson (gauge and fermion) actions. However, it does not bring studies with Wilson-type quarks to the same level as those using the Kogut--Susskind formulation.

hep-lat↗