arXiv subjects

C. DeTar

Publications and source records attributed to C. DeTar.

155 records · Page 9Linked to original sources

arXiv1996

Update on $f_B$

We describe the current status of the MILC collaboration computation of $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios. Progress over the past year includes: better statistics and plateaus at $β=6.52$ (quenched), $β=5.6$ ($N_F=2$) and $β=5.445$ ($N_F=2$), new runs with a wide range of dynamical quark masses at $β=5.5$ ($N_F=2$), an estimate of the systematic errors due to the chiral extrapolation, and an improved analysis which consistently takes into account both the correlations in the data at every stage and the systematic effects due to changing fitting ranges.

hep-lat↗

arXiv1995

The $N_t=6$ equation of state for two flavor QCD

We improve the calculation of the equation of state for two flavor QCD by simulating on $N_t=6$ lattices at appropriate values of the couplings for the deconfinement/chiral symmetry restoration crossover. For $am_q=0.0125$ the energy density rises rapidly to approximately 1 ${\rm GeV/fm^3}$ just after the crossover($m_π/m_ρ\approx 0.4$ at this point). Comparing with our previous result for $N_t=4$~\cite{eos}, we find large finite $N_t$ corrections as expected from free field theory on finite lattices. We also provide formulae for extracting the speed of sound from the measured quantities.

hep-lat↗

arXiv1995

The continuum limit in the quenched approximation

Previous work at $6/g^2=5.7$ with quenched staggered quarks is extended with new calculations at 5.85 and 6.15 on lattices up to $32^3\times 64$. These calculations allow a more detailed study of extrapolation in quark mass, finite volume and lattice spacing than has heretofore been possible. We discuss how closely the quenched spectrum approaches that of the real world.

hep-lat↗

arXiv1995

Two-flavor staggered-fermion thermodynamics at $N_t = 12$

We present new results in an ongoing study of the nature of the high temperature crossover in QCD with two light fermion flavors. These results are obtained with the conventional staggered fermion action at the smallest lattice spacing to date---approximately 0.1 fm. Of particular interest are a study of the temperature of the crossover, an important indicator of continuum scaling, a determination of the induced baryon charge and baryon susceptibility, used to study the dissolution of hadrons at the crossover, the scalar susceptibility, a signal for the appearance of soft modes, and the chiral order parameter, used to test models of critical behavior.

hep-lat↗

arXiv1995

$f_B$ quenched and unquenched

Results for $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$, and their ratios are presented. High statistics quenched runs at $β=5.7$, $5.85$, $6.0$, and $6.3$, plus a run still in progress at $β=6.52$ make possible a preliminary extrapolation to the continuum. The data allows good control of all systematic errors except for quenching, although not all of the error estimates have been finalized. Results from configurations which include effects of dynamical quarks show a significant deviation from the quenched results and make possible a crude estimate of the quenching error.

hep-lat↗

arXiv1995

Status and prospect for determining $f_B$, $f_{B_s}$, $f_{B_s} / f_B$ on the lattice

Preliminary results from the MILC collaboration for $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios are presented. We compute in the quenched approximation at $β=6.3$, 6.0 and 5.7 with Wilson light quarks and static and Wilson heavy quarks. We attempt to quantify all systematic errors other than quenching, and have a first indication of the size of quenching errors.

hep-ph↗

arXiv1994

Thermal Phase Transition in Mixed Action SU(3) Lattice Gauge Theory and Wilson Fermion Thermodynamics

We study the thermal phase diagram of pure SU(3) lattice gauge theory with fundamental and adjoint couplings. We improve previous estimates of the position of the bulk transition line and determine the thermal deconfinement transition lines for $N_t=2,4,6,$ and 8. The endpoint of the bulk transition line $(β_f, β_a)=(4.00(7), 2.06(8))$ improves upon earlier estimates obtained using smaller lattice sizes. For $N_t > 4$ the deconfinement transition line splits cleanly away from the bulk transition line. With increasing $N_t$ the thermal deconfinement transition lines shift to increasingly weaker coupling, joining onto the bulk transition line at increasingly larger $β_a$ in a pattern consistent with the usual universality picture of lattice gauge theories. We also discuss the possible consequences of an induced adjoint term from the fermionic determinant and determine this induced term numerically with a microcanonical demon method for two flavors of dynamical Wilson fermions.

hep-lat↗

arXiv1994

Finite temperature QCD: progress and outstanding problems

I review recent progress in numerical simulations of finite temperature quantum chromodynamics and discuss the status of some outstanding problems. Included is (1) a discussion of recent results determining the temperature of the ``phase transition'' in full QCD, (2) a scaling analysis of the Polyakov loop variable, leading to the determination of a constituent quark free energy, (3) studies of critical behavior near the phase transition in two-flavor QCD, (4) a discussion of problems and new results in thermodynamic simulations with Wilson fermions, (5) recent results in pure gauge theory with a mixed fundamental/adjoint action, and (6) the nonperturbative determination of the equation of state with dynamical fermions included. Finally I mention briefly new developments in efforts to construct a phenomenology of deconfinement and chiral symmetry restoration, namely (7) the dual superconducting model and (8) the instanton model.

hep-lat↗

arXiv1994

Preliminary heavy-light decay constants from the MILC collaboration

Preliminary results from the MILC collaboration for $f_B$, $f_{B_s}$, $f_D$, $f_{D_s}$ and their ratios are presented. We compute in the quenched approximation at $β=6.3$, 6.0 and 5.7 with Wilson light quarks and static and Wilson heavy quarks. We attempt to quantify systematic errors due to finite volume, finite lattice spacing, large $am$, and fitting and extrapolation uncertainties. The hopping parameter approach of Henty and Kenway is used to treat the heavy quarks; the sources are Coulomb gauge gaussians.

hep-lat↗

arXiv1992

Baryon Density Correlations in the Quark Plasma, MIMD Lattice Calculation

As part of an ongoing effort to characterize the high temperature phase of QCD, we measure the quark baryon density in the vicinity of a fixed test quark and compare it with similar measurements at low temperature and at the crossover temperature. Such an observable has also been studied by the Vienna group. We find an extremely weak correlation at high temperature, suggesting that small color singlet clusters are unimportant in the thermal ensemble. We also find that at T = 0.75 T_c the induced quark number shows a surprisingly large component attributable to baryonic screening. A simulation of a simple flux tube model produces results that suggest a plausible scenario: As the crossover temperature is approached from below, baryonic states proliferate. Above the crossover temperature the mean size of color singlet clusters grows explosively, resulting in an effective electrostatic deconfinement.

hep-lat↗

arXiv1992

Finite Size Effects on the QCD Spectrum Revisited

We have continued our study of finite size effects in the QCD spectrum on lattices ranging in size from $8^3\times 24$ to $16^3\times24$. We have increased our statistics for quark mass $am_q=0.025$ for the smallest lattice size. In addition, we have studied quark mass 0.0125 for lattice sizes $12^3\times24$ and $16^3\times24$. These lattice sizes correspond to a box 1.8--3.6 fm on a side when the rho mass at zero quark mass is used to set the scale. We discuss the nucleon to rho mass ratio at a smaller value of $m_π/m_ρ$ than previously studied with two dynamical flavors.

hep-lat↗