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Huey-Wen Lin

Publications and source records attributed to Huey-Wen Lin.

168 records · Page 10Linked to original sources
arXiv2006

Relativistic Heavy Quark Effective Action

We study the fermion action needed to accurately describe the low energy physics of systems including heavy quarks in lattice QCD even when the heavy fermion mass $m$ is on the order of, or larger than, the inverse lattice spacing: $m \ge 1/a$. We carry out an expansion through first order in $|\vec p| a$ (where $\vec p$ is the heavy quark momentum) and all orders in $ma$, refining the analysis of the Fermilab and Tsukuba groups. We demonstrate that the spectrum of heavy quark bound states can be determined accurately through $|\vec p| a$ and $(ma)^n$ for arbitrary exponent $n$ by using a lattice action containing only three unknown coefficients: $m_0$, $ζ$ and $c_P$ (a generalization of $c_{SW}$), which are functions of $ma$. In a companion paper, we show how these three coefficients can be precisely determined using non-perturbative techniques.

hep-lat↗
arXiv2006

Charm as a domain wall fermion in quenched lattice QCD

We report a study describing the charm quark by a domain-wall fermion (DWF) in lattice quantum chromodynamics (QCD). Our study uses a quenched gauge ensemble with the DBW2 rectangle-improved gauge action at a lattice cutoff of $a^{-1} \sim 3$ GeV. We calculate masses of heavy-light (charmed) and heavy-heavy (charmonium) mesons with spin-parity $J^P = 0^\mp$ and $1^\mp$, leptonic decay constants of the charmed pseudoscalar mesons ($D$ and $D_s$), and the $D^0$-$\bar{D^0}$ mixing parameter. The charm quark mass is found to be $m^{\bar{\rm MS}}_{c}(m_{c})=1.24(1)(18)$ GeV. The mass splittings in charmed-meson parity partners $Δ_{q,J=0}$ and $Δ_{q, J=1}$ are degenerate within statistical errors, in accord with experiment, and they satisfy a relation $Δ_{q=ud, J} > Δ_{q=s, J}$, also consistent with experiment. A C-odd axial vector charmonium state, $h_c), lies 22(11) MeV above the $χ_{c1}$ meson, or $m_{h_{c}} = 3533(11)_{\rm stat.}$ MeV using the experimental $χ_{c1}) mass. However, in this regard, we emphasize significant discrepancies in the calculation of hyperfine splittings on the lattice. The leptonic decay constants of $D$ and $D_s$ mesons are found to be $f_D=232(7)_{\rm stat.}(^{+6}_{-0})_{\rm chiral}(11)_{\rm syst.}$ MeV and $f_{D_s}/f_{D} = 1.05(2)_{\rm stat.}(^{+0}_{-2})_{\rm chiral}(2)_{\rm syst.}$, where the first error is statistical, the second a systematic due to chiral extrapolation and the third error combination of other known systematics. The $D^0$-$\bar{D^0}$ mixing bag parameter, which enters the $ΔC = 2$ transition amplitude, is found to be $B_D(2{GeV})=0.845(24)_{\rm stat.}(^{+24}_{-6})_{\rm chiral}(105)_{\rm syst.}$.

hep-lat↗
arXiv2005

Non-perturbatively determined relativistic heavy quark action

Preliminary results are presented in a step scaling determination of the coefficients in the relativistic heavy quark action. By matching finite volume, heavy-heavy and heavy-light meson masses, we attempt to determine the four parameters ($m$, $ζ$, $c_B$ and $c_E$) in the on-shell-improved, heavy quark action. In this report we carry out one step in this program by matching two physically equivalent systems. The first is a fully relativistic calculation using a $24^3\times 48$, $1/a=5.4$ GeV lattice with both the heavy and light quarks treated as domain wall fermions. The second calculation uses at $16^3\times 32$, $1/a=3.6$ GeV lattice, a domain-wall light quark and a heavy quark computed with the relativistic heavy quark action. The four parameters in this heavy quark effective action are then varied to reproduce the mass spectrum from the first calculation. These calculations are carried out in the quenched approximation for a heavy quark mass approximately that of the charmed quark.

hep-lat↗
arXiv2005

Quark-gluon vertex with an off-shell O(a)-improved chiral fermion action

We perform a study the quark-gluon vertex function with a quenched Wilson gauge action and a variety of fermion actions. These include the domain wall fermion action (with exponentially accurate chiral symmetry) and the Wilson clover action both with the non-perturbatively improved clover coefficient as well as with a number of different values for this coefficient. We find that the domain wall vertex function behaves very well in the large momentum transfer region. The off-shell vertex function for the on-shell improved clover class of actions does not behave as well as the domain wall case and, surprisingly, shows only a weak dependence on the clover coefficient $c_{SW}$ for all components of its Dirac decomposition and across all momenta. Including off-shell improvement rotations for the clover fields can make this action yield results consistent with those from the domain wall approach, as well as helping to determine the off-shell improved coefficient $c_q^\prime$.

hep-lat↗
arXiv2004

Non-perturbative determination of heavy quark action coefficients

We propose to determine the coefficients in the Fermilab heavy quark action by matching the finite-volume, off-shell, gauge-fixed propagator and vertex functions with those determined in the exact, relativistic theory. The matching relativistic amplitudes may be determined either from short-distance perturbation theory or from finite-volume step-scaling recursion. Tree-level matching and non-perturbative off-shell amplitudes are presented.

hep-lat↗