著者

Aoki S. Boyd G. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.67, no.3, pp.034503, 2003-02

被引用文献数

75

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We present the details of simulations for the light hadron spectrum in quenched QCD carried out on the CP-PACS parallel computer. Simulations are made with the Wilson quark action and the plaquette gauge action on lattices of size 323×56–643×112 at four values of lattice spacings in the range a≈0.1–0.05 fm and spatial extent Lsa≈3 fm. Hadronic observables are calculated at five quark masses corresponding to mPS/mV≈0.75–0.4, assuming the u and d quarks are degenerate, but treating the s quark separately. We find that the presence of quenched chiral singularities is supported from an analysis of the pseudoscalar meson data. The physical values of hadron masses are determined using mπ, mρ, and mK (or mφ) as input to fix the physical scale of lattice spacing and the u, d, and s quark masses. After chiral and continuum extrapolations, the agreement of the calculated mass spectrum with experiment is at a 10% level. In comparison with the statistical accuracy of 1%–3% and systematic errors of at most 1.7% we have achieved, this demonstrates a failure of the quenched approximation for the hadron spectrum: the hyperfine splitting in the meson sector is too small, and in the baryon sector the octet masses and mass splitting of the decuplet are both smaller than experiment. Light quark masses are calculated using two definitions: the conventional one and the one based on the axial-vector Ward identity. The two results converge toward the continuum limit, yielding mud=4.29(14)-0.79+0.51 MeV where the first error is statistical and the second one is systematic due to chiral extrapolation. The s quark mass depends on the strange hadron mass chosen for input: ms=113.8(2.3)-2.9+5.8 MeV from mK and ms=142.3(5.8)-0+22.0 MeV from mφ, indicating again a failure of the quenched approximation. We obtain the scale of QCD, ΛMS̅ (0)=219.5(5.4) MeV with mρ used as input. An O(10%) deviation from experiment is observed in the pseudoscalar meson decay constants.

著者

Khan A. Ali Aoki S. Boyd G. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.65, no.5, pp.054505, 2002-02

被引用文献数

195 138

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We present results of a numerical calculation of lattice QCD with two degenerate flavors of dynamical quarks, identified with up and down quarks, and with a strange quark treated in the quenched approximation. The lattice action and simulation parameters are chosen with a view to carrying out an extrapolation to the continuum limit as well as chiral extrapolations in dynamical up and down quark masses. Gauge configurations are generated with a renormalization-group improved gauge action and a mean field improved clover quark action at three values of β=6/g2, corresponding to lattice spacings of a≈0.22, 0.16 and 0.11 fm, and four sea quark masses corresponding to mPS/mV≈0.8, 0.75, 0.7 and 0.6. The sizes of lattice are chosen to be 123×24, 163×32 and 243×48 so that the physical spatial size is kept constant at La≈2.5 fm. Hadron masses, light quark masses and meson decay constants are measured at five valence quark masses corresponding to mPS/mV≈0.8, 0.75, 0.7, 0.6 and 0.5. We also carry out complementary quenched simulations with the same improved actions. The quenched spectrum from this analysis agrees well in the continuum limit with the one of our earlier work using the standard action, quantitatively confirming the systematic deviation of the quenched spectrum from experiment. We find the two-flavor full QCD meson masses in the continuum limit to be much closer to experimental meson masses than those from quenched QCD. When using the K meson mass to fix the strange quark mass, the difference between quenched QCD and experiment of 2.6-0.9+0.3% for the K* meson mass and of 4.1-1.6+0.5% for the φ meson mass is reduced to 0.7-1.7+1.1% and 1.3-2.5+1.8% in full QCD, where the errors include estimates of systematic errors of the continuum extrapolation as well as statistical errors. Analyses of the J parameter yield a similar trend in that the quenched estimate in the continuum limit J=0.375-0.009+0.039 increases to J=0.440-0.031+0.061 in two-flavor full QCD, approaching the experimental value J≈0.48. We take these results as manifestations of sea quark effects in two-flavor full QCD. For baryon masses full QCD values for strange baryons such as Ξ and Ω are in agreement with experiment, while they differ increasingly with decreasing strange quark content, resulting in a nucleon mass higher than experiment by 10% and a Δ mass by 13%. The pattern suggests finite size effects as a possible origin for this deviation. For light quark masses in the continuum limit we obtain mudMS̅ (2 GeV)=3.44-0.22+0.14 MeV and msMS̅ (2 GeV)=88-6+4 MeV (K-input) and msMS̅ (2 GeV)=90-11+5 MeV (φ-input), which are reduced by about 25% compared to the values in quenched QCD. We also present results for decay constants where large scaling violations obstruct a continuum extrapolation. The need for a nonperturbative estimate of renormalization factors is discussed.

著者

Khan A. Ali Aoki S. Aoki Y. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Izubuchi T. Kanaya K. Kaneko T. Kuramashi Y. Nagai K. I. Okawa M. Shanahan H. P. Taniguchi Y. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.64, no.11, pp.114506, 2001-11

被引用文献数

43 91

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We report on a calculation of BK with domain-wall fermion action in quenched QCD. Simulations are made with a renormalization group improved gauge action at β=2.6 and 2.9 corresponding to a-1≈2 and 3 GeV. Effects due to finite fifth dimensional size N5 and finite spatial size Nσ are examined in detail. Matching to the continuum operator is made perturbatively at one loop order. We obtain BK(μ=2 GeV)=0.5746(61)(191), where the first error is statistical and the second error represents an estimate of scaling violation and O(α2) errors in the renormalization factor added in quadrature, as an estimate of the continuum value in the modified minimal subtraction (MS̅ ) scheme with naive dimensional regularization. This value is consistent, albeit somewhat small, with BK(μ=2 GeV)=0.628(42) obtained by the JLQCD Collaboration using the Kogut-Susskind quark action. Results for light quark masses are also reported.

著者

Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.64, no.11, pp.114501, 2001-10

被引用文献数

24 40

---

We present a study of the topological susceptibility in lattice QCD with two degenerate flavors of dynamical quarks. The topological charge is measured on gauge configurations generated with a renormalization group improved gauge action and a mean field improved clover quark action at three values of β=6/g2 with four sea quark masses at each β. The lattice spacings at these β’s are a≈0.22, 0.16 and 0.11 fm at the physical up and down quark mass, which are fixed by the physical ρ meson mass. The study is supplemented by simulations of pure SU(3) gauge theory with the same gauge action at 5 values of β with lattice spacings 0.09 fm≲a≲0.27 fm. We employ a field-theoretic definition of the topological charge together with cooling. For the topological susceptibility in the continuum limit of pure SU(3) gauge theory we obtain χt1/4=197-16+13 MeV where the error shows statistical and systematic ones added in quadrature. In full QCD χt at heavy sea quark masses is consistent with that of pure SU(3) gauge theory. A decrease of χt toward light quark masses, as predicted by the anomalous Ward-Takahashi identity for U(1) chiral symmetry, becomes clearer for smaller lattice spacings. The cross over in the behavior of χt from heavy to light sea quark masses is discussed.

著者

Manke T. Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.64, no.9, pp.097505, 2001-10

被引用文献数

12

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We present a dynamical lattice calculation with two flavors for bottomonium states with an additional gluonic excitation. Using improved actions for the quarks and gauge fields at a lattice spacing of a≈0.1 fm, we find 10.977(61)(62) GeV for the energy of the lowest lying bb̅ g hybrid, where the first error is statistical and the second denotes the systematic uncertainty due to the determination of scale. In a parallel quenched simulation we demonstrate explicitly that vacuum polarization effects are less than 10% of the splitting with the ground state.

著者

Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K.-I. Okamoto M. Okawa M. Shanahan H. P. Taniguchi Y. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.64, no.7, pp.074510, 2001-09

被引用文献数

91

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We present the results of a first study of the equation of state in finite-temperature QCD with two flavors of Wilson-type quarks. The simulations are made on lattices with a temporal size Nt=4 and 6, using a renormalization-group-improved action for the gluon sector and a mean-field-improved clover action for the quark sector. The lines of constant physics corresponding to fixed values of the ratio mPS/mV of the pseudoscalar to vector meson masses at zero temperature are determined, and the beta functions which describe the renormalization-group flow along these lines are calculated. Using these results, the energy density and the pressure are calculated as functions of temperature along the lines of constant physics in the range mPS/mV=0.65–0.95. The quark mass dependence in the equation of state is found to be small for mPS/mV≲0.8. A comparison of the results for Nt=4 and Nt=6 lattices shows a significant scaling violation present in the Nt=4 results. At high temperatures the results for Nt=6 are quite close to the continuum Stefan-Boltzmann limit, suggesting the possibility of a precise continuum extrapolation of thermodynamic quantities from simulations at Nt≳6.

著者

Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.64, no.5, pp.054504, 2001-08

被引用文献数

34 81

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We present a study of leptonic B meson decay constants in lattice QCD with two flavors (Nf=2) of light dynamical quarks using nonrelativistic QCD for the heavy quark. Gauge configurations are generated with a renormalization-group improved gauge action and a mean-field-improved clover light quark action. Measurements are carried out at two values of β=6/g2, each for four sea quark masses, corresponding to inverse lattice spacings a-1≈1.3 and 1.8 GeV in the chiral limit of the sea quark. The continuum values of the decay constants are derived by evaluating the discretization errors at each finite lattice spacing. We find fBNf=2=204(8)(29)(+44) MeV, fBsNf=2=242(9)(34)(+38) MeV, and fBsNf=2/fBNf=2=1.179(18)(23), where the errors listed are statistical, systematic and uncertainty due to choice of the physical quantity used to fix the scale. Comparison is made to quenched results (Nf=0) obtained with the same action combination and matching lattice spacings. We find fBNf=2/fBNf=0=1.07(5), fBsNf=2/fBsNf=0=1.10(5) and (fBs/fB)Nf=2/(fBs/fB)Nf=0=1.03(2), which indicate a 5–10 % increase in the values of the decay constants, but no appreciable change in the ratio fBs/fB, due to sea quarks.

著者

Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.64, no.3, pp.034505, 2001-07

被引用文献数

30 98

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We present a calculation of the B and D meson decay constants in lattice QCD with two (Nf=2) flavors of light dynamical quarks, using an O(a)-improved Wilson action for both light and heavy quarks and a renormalization-group improved gauge action. Simulations are made at three values of lattice spacing a=0.22,0.16,0.11 fm and four values of sea quark mass in the range mPS/mV≈0.8-0.6. Our provisional estimate for the continuum values of the decay constants are fBd=208(10)(29) MeV, fBs=250(10)(35)(-0+8) MeV, fDd=225(14)(40) MeV, fDs=267(13)(48)(-0+10) MeV for Nf=2 where the statistical and systematic errors are separately listed, and the third error for fBs and fDs shows the uncertainty of the determination of the strange quark mass. We also carry out a set of quenched simulations using the same action to make a direct examination of sea quark effects. Taking the ratio of results for Nf=2 and Nf=0, we obtain fBdNf=2/fBdNf=0=1.11(6),fBsNf=2/fBsNf=0=1.14(5),fDdNf=2/fDdNf=0=1.03(6),fDsNf=2/fDsNf=0=1.07(5). They show a 10–15 % increase in the Nf=2 results over those of Nf=0 for the B meson decay constants, while evidence for such a trend is statistically less clear for the D meson decay constants.

著者

Khan A. Ali Aoki S. Aoki Y. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Izubuchi T. Kanaya K. Kaneko T. Kuramashi Y. Manke T. Nagai K. I. Noaki J. Okawa M. Shanahan H. P. Taniguchi Y. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.63, no.11, pp.114504, 2001-05

被引用文献数

47 61

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We investigate the chiral properties of quenched domain-wall QCD (DWQCD) at the lattice spacings a-1≃1 and 2 GeV for both plaquette and renormalization-group (RG) improved gauge actions. In the case of the plaquette action we find that the quark mass defined through the axial Ward-Takahashi identity remains non-vanishing in the DWQCD chiral limit that the bare quark mass mf→0 and the length of the fifth dimension Ns→∞, indicating that chiral symmetry is not realized with quenched DWQCD up to a-1≃2 GeV. The behavior is much improved for the RG-improved gauge action: while a nonvanishing quark mass remains in the chiral limit at a-1≃1 GeV, the result at a-1≃2 GeV is consistent with an exponentially vanishing quark mass in the DWQCD chiral limit, indicating the realization of exact chiral symmetry. An interpretation and implications are briefly discussed.

著者

Manke T. Khan A. Ali Aoki S. Burkhalter R. Ejiri S. Fukugita M. Hashimoto S. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Nagai K. Okawa M. Shanahan H. P. Ukawa A. Yoshié T.

出版者

American Physical Society

雑誌

Physical review D (ISSN:05562821)

巻号頁・発行日

vol.62, no.11, pp.114508, 2000-11

被引用文献数

32

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We study the effects of two dynamical sea quarks on the spectrum of heavy quarkonia. Within the non-relativistic approach to lattice QCD we find sizable changes to the hyperfine splitting, but we do not observe any changes for the fine structure. We also investigate the scaling behavior of our results for several different lattice spacings.