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JLQCD Collaboration

Publications and source records attributed to JLQCD Collaboration.

71 records · Page 4Linked to original sources
arXiv1997

Heavy quark mass dependence of semileptonic form factors for B decays

We present our study of the dependence of the heavy-to-light semileptonic B decay form factors on the heavy-light meson mass $M_{PS}$. Simulations are made over a range of the heavy quark mass covering both the charm and bottom quarks using the $O(a)$-improved clover action at $β=5.9$ on a $16^3\times 40$ and $24^3\times 64$ lattice. We find that a weak dependence of form factors on $M_{PS}$ observed in previous studies in the region of charm quark persists up to the region of$b$ quark. The soft pion relation $f^0(q^2_{max})=f_B/f_π$ is examined and found to be largely violated.

hep-lat↗
arXiv1997

The Kaon B-parameter with the Wilson Quark Action using Chiral Ward Identities

We present a detailed description of the method and results of our calculation of the kaon B parameter using the Wilson quark action in quenched QCD at $β=5.9-6.5$. The mixing problem of the $Δs=2$ four-quark operators is solved non-perturbatively with full use of chiral Ward identities. We find $B_K(NDR, 2 GeV)=0.562(64)$ in the continuum limit, which agrees with the value obtained with the Kogut-Susskind quark action.

hep-lat↗
arXiv1997

The Light Quark Masses with the Wilson Quark Action using Chiral Ward Identities

We present results for the light quark masses for the Wilson quark action obtained with the PCAC relation for the one-link extended axial vector current in quenched QCD at $β=5.9-6.5$. This method leads to a remarkable improvement of scaling behavior of the light quark masses compared to the conventional method. We obtain ${\bar m}_l=3.87(37)$MeV for the averaged up and down quark mass and ${\bar m}_s=97(9)$MeV for the strange quark mass in the ${\barMS}$ scheme at $μ=2$GeV.

hep-lat↗
arXiv1997

$K^{+}\toπ^{+}π^{0}$ Decay Amplitude in Quenched Lattice QCD

A new study is reported of a lattice QCD calculation of the $K^+\toπ^+ π^0 $ decay amplitude with the Wilson quark action in the quenched approximation at $β=6.1$. The amplitude is extracted from the $K\toππ$ Green function, and a conversion to the continuum value is made employing a recent one-loop calculation of chiral perturbation theory. The result is consistent with the experimental value if extrapolated to the chiral limit.

hep-lat↗
arXiv1997

Kaon B parameter from quenched Lattice QCD

We present results of a large-scale simulation for the Kaon B parameter $B_K$ in quenched lattice QCD with the Kogut-Susskind quark action. Calculating $B_K$ at 1% statistical accuracy for seven values of lattice spacing in the range $a\approx 0.24-0.04$ fm on lattices up to $56^3\times 96$, we verify a quadratic $a$ dependence of $B_K$ theoretically predicted. Strong indications are found that, with our level of accuracy, $α_{\bar{MS}}(1/a)^2$ terms arising from our one-loop matching procedure have to be included in the continuum extrapolation. We present $B_K$(NDR, 2 GeV)=0.628(42) as our final value, as obtained by a fit including the $α_{\bar{MS}}(1/a)^2$ term.

hep-lat↗
arXiv1997

Results for Quenched $B_K$ from JLQCD

A report is presented on our continued effort to elucidate the continuum limit of $B_K$ using the quenched Kogut-Susskind quark action. By adding to our previous simulations one more point at $β= 6.65$ employing a $56^3\times 96$ lattice, we now confirm the expected $O(a^2)$ behavior of $B_K$ with the Kogut-Susskind action. A simple continuum extrapolation quadratic in $a$ leads to $B_K$(NDR, 2 GeV) = 0.598(5). As our final value of $B_K$ in the continuum we present $B_K$(NDR, 2 GeV)=0.628(42), as obtained by a fit including an $α_{\bar{MS}}(1/a)^2$ term arising from the lattice-continuum matching with the one-loop renormalization.

hep-lat↗
arXiv1997

Two-Flavor Chiral Phase Transition in Lattice QCD with the Kogut-Susskind Quark Action

A summary is presented of a scaling study of the finite-temperature chiral phase transition of two-flavor QCD with the Kogut-Susskind quark action based on simulations on $L^3\times4$ ($L$=8, 12 and 16) lattices at the quark mass of $m_q=0.075, 0.0375, 0.02$ and 0.01. We find a phase transition to be absent for $m_q\geq 0.02$, and also quite likely at $m_q=0.01$. The quark mass dependence of susceptibilities is consistent with a second-order transition at $m_q=0$. The exponents, however, deviate from the O(2) and O(4) values theoretically expected.

hep-lat↗
arXiv1997

Scaling Study of the Two-Flavor Chiral Phase Transition with the Kogut-Susskind Quark Action in Lattice QCD

We report on a study of two-flavor finite-temperature chiral phase transition employing the Kogut-Susskind quark action and the plaquette gluon action in lattice QCD for a lattice with $N_t=4$ temporal size. Hybrid R simulations of $10^4$ trajectories are made at quark masses of $m_q=0.075, 0.0375, 0.02, 0.01$ in lattice units for the spatial sizes $8^3, 12^3$ and $16^3$. The spatial size dependence of various susceptibilities confirm the previous conclusion of the absence of a phase transition down to $m_q=0.02$. At $m_q=0.01$ an increase of susceptibilities is observed up to the largest volume $16^3$ explored in the present work. We argue, however, that this increase is likely to be due to an artifact of too small a lattice size and it cannot be taken to be the evidence for a first-order transition. Analysis of critical exponents estimated from the quark mass dependence of susceptibilities shows that they satisfy hyperscaling consistent with a second-order transition located at $m_q=0$. The exponents obtained from larger lattice, however, deviate significantly from both those of O(2), which is the exact symmetry group of the Kogut-Susskind action at finite lattice spacing, and those of O(4) expected from an effective sigma model analysis in the continuum limit.

hep-lat↗
arXiv1997

Scaling Analysis of Chiral Phase Transition for Two Flavors of Kogut-Susskind Quarks

Report is made of a systematic scaling study of the finite-temperature chiral phase transition of two-flavor QCD with the Kogut-Susskind quark action based on simulations on $L^3\times4$ ($L$=8, 12 and 16) lattices at the quark mass of $m_q=0.075, 0.0375, 0.02$ and 0.01. Our finite-size data show that a phase transition is absent for $m_q\geq 0.02$, and quite likely also at $m_q=0.01$. The scaling behavior of susceptibilities as a function of $m_q$ is consistent with a second-order transition at $m_q=0$. However, the exponents deviate from the O(2) or O(4) values theoretically expected.

hep-lat↗
arXiv1997

Lattice QCD Calculation of the Kaon B-parameter with the Wilson Quark Action

The kaon B parameter is calculated in quenched lattice QCD with the Wilson quark action. The mixing problem of the Δs=2 four-quark operators is solved non-perturbatively with full use of chiral Ward identities, and this method enables us to construct the weak four-quark operators exhibiting good chiral behavior. We find B_K(NDR, 2GeV)=0.562(64) in the continuum limit, which agrees with the value obtained with the Kogut-Susskind quark action.

hep-lat↗
arXiv1996

Topics in Light Hadron Mass Spectrum in Quenched QCD

Several topics concerning the light hadron spectrum are discussed. Flavor symmetry breaking effects and the problem of quenched chiral logarithm are examined with pion mass data for the Kogut-Susskind quark action, and light meson decay constants for the Wilson action calculated with non-perturbative renormalization constants are discussed. Results for quark masses are also given both for the Kogut-Susskind and Wilson actions.

hep-lat↗
arXiv1996

Continuum Limit of the Heavy-Light Decay Constant with the Quenched Wilson Quark Action

We explore the problems in calculating the decay constant for heavy-light mesons using the quenched Wilson quark action for both heavy and light quarks. We find that the continuum limit of the decay constant is reasonably converged among different prescriptions after the continuum limit is taken. A number of technical problems associated with prescriptions are also addressed.

hep-lat↗
arXiv1996

Toward the Continuum Limit of $B_K$ with the Quenched Kogut-Susskind Quark Action

We present new results of our ongoing project toward a precision determination of the kaon $B$ parameter with the Kogut-Susskind quark action in quenched QCD. New results taken at $β$=6.4 and $β=5.7$ suggest that an apparently linear $a$ dependence of $B_K$ previously observed for $β=5.85-6.2$ arises from a change of curvature from convex to concave as the lattice spacing is reduced. Fitting data for $β\geq 5.93$ with an $O(a^2)$ form yields $B_K$(NDR,2 GeV)=0.587(7)(17) in the continuum limit. We also describe a finite-size study of $B_K$ at $β=$ 6.0 and 6.4, and a reanalysis of the theoretical argument for $O(a^2)$ behavior.

hep-lat↗
arXiv1995

Heavy-Light Matrix Elements with the Wilson Quark Action

Status report is made of our quenched study of heavy-light matrix elements employing the Wilson quark action for heavy quark. Results obtained up to now with 200 configurations at $β=6.1$ on a $24^3\times64$ lattice and with 100 configurations at $β=6.3$ on a $32^3 \times80$ lattice suggest that the pseudoscalar decay constant varies little over this range of $β$ in both charm and bottom regions. Results for the $B$ parameter are also reported.

hep-lat↗
arXiv1995

Analysis of Hadron Propagators with One Thousand Configurations on a $24^3\times 64$ Lattice at $β=6.0$

Statistical properties of effective mass are analyzed. We show from a general ground that effective mass as a function of time should not exhibit long plateaux whatever high statistics simulations are made: the mass should fluctuate beyond the one standard deviation of error bars after a few time slices for large times where the ground state dominates. This explains the difficulty of obtaining long plateaux experienced in previous simulations. Implications of the observation for global $χ^2$ fits are discussed, and results for hadron masses are presented.

hep-lat↗
arXiv1995

Toward Precision Measurement of $B_K$ with Quenched Kogut-Susskind Quarks

We present a status report of our ongoing effort toward a precision determination of the kaon $B$ parameter with the Kogut-Susskind quark action in quenched QCD. Results for $B_K$ so far accumulated at $β=5.85$, 5.93, 6.0 and 6.2 corresponding to $a^{-1}=1.3-2.6$ GeV do not exhibit the theoretically expected $O(a^2)$ behavior, but are apparently more consistent with an $O(a)$ behavior.

hep-lat↗