Heavy-light Decay Constants Research Articles

Heavy-light decay constants from clover heavy quark action in QCD with two flavors of dynamical quarks

We present results on an analysis of the decay constants f Bd and f Bs with two flavours of sea quark. The calculation has been carried out on 3 different bare gauge couplings and 4 sea quark masses at each gauge coupling, with m π / m ϱ ranging from 0.8 to 0.6. We employ the Fermilab formalism to perform calculations with heavy quarks whose mass is in the range of the b-quark. A detailed comparison with a quenched calculation using the same action is made to elucidate the effects due to the sea quarks.

Heavy-light decay constants from clover heavy quark action in QCD with two flavors of dynamical quarks

Heavy-light decay constants from clover heavy quark action in QCD with two flavors of dynamical quarks

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

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

Neutral B meson mixing and heavy-light decay constants from quenched lattice QCD

We present high-statistics results for neutral B-meson mixing and heavy-light-meson leptonic decays in the quenched approximation from tadpole-improved clover actions at β = 6.0 and β = 6.2. We consider quantities such as B B d(s) , f D d(s) , f B d(s) and the full Δ B = 2 matrix elements as well as the corresponding SU(3)-breaking ratios. These quantities are important for determining the CKM matrix element | V td |.

Heavy quark physics in N f = 2 QCD

We present a preliminary analysis of the heavy-heavy spectrum and heavy-light decay constants in full QCD, using a tadpole-improved SW quark action and an RG-improved gauge action on a 16 3 × 32 lattice with four sea quark masses corresponding to m π/ m ρ ≈ 0.8, 0.75, 0.7, 0.6 and a −1 ≈ 1.3 GeV. We focus particularly on the effect of sea quarks on these observables.

Heavy-light decay constants: conclusions from the Wilson action

We report on the results of a MILC collaboration calculation of f B , f B s , f D , f D s , and their ratios. We discuss the most important errors in more detail than we have elsewhere.

New results from APE with nonperturbatively improved Wilson fermions

We present the results for hadronic spectrum, decay constants and the light quark masses obtained with non-perturbatively improved Wilson fermions. We also give our preliminary results for the heavy-light decay constants.

Quenched hadron spectrum and decay constants on the lattice

Abstract In this talk we present the results obtained from a study of O(2000) (quenched) lattice configuration from the APE collaboration, at 6.0 ⩽ Q ⩽ 6.4, using both the Wilson and the SW-Clover fermion action. We determine the light hadronic spectrum and the meson decay constants. For the light-light systems we find an agreement with the experimental data of ∼ 5∼ for mesonic masses and ∼ 10∼-15∼ for baryonic masses and pseudoscalar decay constants; a larger deviation is present for the vector decay constants. For the heavy-light decay constants we find fD1 = 237 ±16MeV, fD = 221 ±17MeV (fD1/fD = 1.07(4)), fB1 = 205±35 MeV, fB = 180±32 McV (fB1/fB = 1.14(8)), in good agreement with previous estimates.

SU(3) flavor breaking in hadronic matrix elements forB−B¯oscillations

Results in the quenched approximation for SU(3) breaking ratios of the heavy-light decay constants and the $\ensuremath{\Delta}F=2$ mixing matrix elements are reported. Using lattice simulations at ${6/g}^{2}=5.7$, 5.85, 6.0, and 6.3, we directly compute the mixing matrix element ${M}_{\mathrm{hl}}=〈{P}_{\mathrm{hl}}|\overline{h}{\ensuremath{\gamma}}_{\ensuremath{\mu}}(1\ensuremath{-}{\ensuremath{\gamma}}_{5})l\overline{h}{\ensuremath{\gamma}}_{\ensuremath{\mu}}(1\ensuremath{-}{\ensuremath{\gamma}}_{5})l|{P}_{\mathrm{hl}}〉.$ Extrapolating to the physical $B$ meson states, ${B}^{0}$ and ${B}_{s}^{0},$ we obtain ${M}_{\mathrm{bs}}{/M}_{\mathrm{bd}}{=1.76(10)}_{\ensuremath{-}42}^{+57}$ in the continuum limit. The systematic error includes the errors within the quenched approximation but not the errors of quenching. We also obtain the ratio of decay constants, ${f}_{\mathrm{bs}}{/f}_{\mathrm{bd}}{=1.17(2)}_{\ensuremath{-}6}^{+12}.$ For the $B$ parameters we find ${B}_{\mathrm{bs}}(2\phantom{\rule{0ex}{0ex}}\mathrm{GeV}{)=B}_{\mathrm{bd}}(2\phantom{\rule{0ex}{0ex}}\mathrm{GeV})=1.02(13);$ we cannot resolve the SU(3) breaking effects in this case.

Heavy-light decay constants from Wilson and static quarks

MILC collaboration results for f B , f B s , f D , f D s and their ratios are presented. These results are still preliminary, but the analysis is close to being completed. Sources of systematic error, both within the quenched approximation and from quenching itself, are estimated. We find, for example, f B = 153±10 −13 −0 +36 +13MeV, and f B s f B = 1.10±0.02 −0.03 −0.02 +0.05 +0.03 , where the errors are statistical, systematic (within the quenched approximation), and systematic (of quenching), respectively. The extrapolation to the continuum and the chiral extrapolation are the largest sources of error. Present central values are based on linear chiral extrapolations; a shift to quadratic extrapolations would raise f B by 20 MeV and make the error within the quenched approximation more symmetric.

Semileptonic form factors

I report the current status of the heavy-light decay constants, the bag parameters and the semileptonic form factors.

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.

B meson decay constant and non-relativistic interpretation of wilson and clover fermion actions for heavy quark

We report on our effort toward a determination of the heavy-light decay constant in quenched QCD. Simulation results are analyzed in terms of the non-relativistic interpretation of relativistic fermions fully incorporating oneloop corrections in the mass and current renormalization factors for massive quark. For the Wilson action for which the analysis is completed, we obtain ƒ d = 192(30)MeV, ƒ d = 214(33)MeV, ƒ b = 171(29)MeV and ƒ b s =193(32)MeV in the continuum limit.

Leptonic Decays of Heavy Quarks on the Lattice

The status of lattice calculations of heavy-light decay constants and of the B parameter BB is reviewed. After describing the lattice approach to heavy quark systems, the main results are discussed, with special emphasis on the systematic errors in present lattice calculations. A detailed analysis of the continuum limit for decay constants is performed. The implications of lattice results on studies of CP violation in the Standard Model are discussed.

Comparison of potential models through heavy quark effective theory.

I calculate heavy-light decay constants in a nonrelativistic potential model. The resulting estimate of heavy quark symmetry breaking conflicts with similar estimates from lattice QCD. I show that a semirelativistic potential model eliminates the conflict. Using the results of heavy quark effective theory allows me to identify and compensate for shortcomings in the model calculations in addition to isolating the source of the differences in the two models. The results lead to a rule as to where the nonrelativistic quark model gives misleading predictions.

Preliminary heavy-light decay constants from the MILC collaboration

Preliminary results from the MILC Collaboration for f{sub B}, f{sub B{sub s}}, f{sub D}, f{sub D{sub s}} and their ratios are presented. We compute in the quenched approximation at {beta} = 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.

Improved currents for heavy quarks

We discuss lattice artifacts for matrix elements of hadrons containing one or more heavy quark. In particular, we analyze interrelations between lattice artifacts and the $1/m_Q$ expansion. The implications for calculations of heavy-light decay constants and of semi-leptonic form factors are discussed.

Computation of the heavy-light decay constant using nonrelativistic lattice QCD.

We report results on a lattice calculation of the heavy-light meson decay constant employing the non-relativistic QCD approach for heavy quark and Wilson action for light quark. Simulations are carried out at $\beta=6.0$ on a $16^3\times 48$ lattice. Signal to noise ratio for the ground state is significantly improved compared to simulations in the static approximation, enabling us to extract the decay constant reliably. We compute the heavy-light decay constant for several values of heavy quark mass and estimate the magnitude of the deviation from the heavy mass scaling law $f_{P} \sqrt{m_{P}} = const$. For the $B$ meson we find $f_{B} = 171\pm 22^{+19}_{-45}$ MeV, while an extrapolation to the static limit yields $f_{B}^{static}$ = $297\pm 36^{+15}_{-30}$ MeV.

Quenched heavy-light decay constants

We present decay constants from a quenched simulation using both propagating quarks and the static theory at β = 6.2 on 24 3 × 48. The results using propagating quarks are used to test scaling laws predicted by the heavy quark symmetry.

Quenched heavy-light decay constants.

We present results for heavy-light decay constants, using both propagating quarks and the static approximation, in $O(a)$-improved, quenched lattice QCD. At $\ensuremath{\beta}=6.2$ on a ${24}^{3}$\ifmmode\times\else\texttimes\fi{}48 lattice we find ${f}_{D}={185}_{\ensuremath{-}3}^{+4}{(\mathrm{stat})}_{\ensuremath{-}7}^{+42}(\mathrm{syst})$ MeV, ${f}_{B}={160}_{\ensuremath{-}6\ensuremath{-}19}^{+6+53}$ MeV, $\frac{{f}_{{D}_{s}}}{{f}_{D}}={1.18}_{\ensuremath{-}2}^{+2}$, and $\frac{{f}_{{B}_{s}}}{{f}_{B}}={1.22}_{\ensuremath{-}3}^{+4}$, in good agreement with earlier studies. From the static theory we obtain ${f}_{B}^{\mathrm{stat}}={253}_{\ensuremath{-}15\ensuremath{-}15}^{+16+105}$ MeV. We also present results from a simulation at $\ensuremath{\beta}=6.0$ on a ${16}^{3}$\ifmmode\times\else\texttimes\fi{}48 lattice, which are consistent with those at $\ensuremath{\beta}=6.2$. In order to study the effects of improvement, we present a direct comparison of the results using both the Wilson and the improved action at $\ensuremath{\beta}=6.0$.