- 著者
- Aoki S. Fukugita M. Hashimoto S. Ishikawa K.-I. Ishizuka N. Iwasaki Y. Kanaya K. Kaneda T. Kaya S. Kuramashi Y. Okawa M. Onogi T. Tominaga S. Tsutsui N. Ukawa A. Yamada N. Yoshié T.
- 出版者
- American Physical Society
- 雑誌
- Physical review D (ISSN:05562821)
- 巻号頁・発行日
- vol.62, no.9, pp.094501, 2000-10
- 被引用文献数
- 14 18
We present a study for the pion decay constant fπ in the quenched approximation to lattice QCD with the Kogut-Susskind (KS) quark action, with the emphasis given to the renormalization problems. Numerical simulations are carried out at the couplings β=6.0 and 6.2 on 323×64 and 483×64 lattices, respectively. The pion decay constant is evaluated for all KS flavors via gauge invariant and noninvariant axial vector currents with the renormalization constants calculated by both the nonperturbative method and perturbation theory. We obtain fπ=89(6) MeV in the continuum limit as the best value using the partially conserved axial vector current, which requires no renormalization. From a study for the other KS flavors we find that the results obtained with the nonperturbative renormalization constants are well convergent among the KS flavors in the continuum limit, confirming restoration of SU(4)A, flavor symmetry, while perturbative renormalization still leaves an apparent flavor breaking effect even in the continuum limit.
- 著者
- Namekawa Y. Aoki S. Fukugita M. Ishikawa K.-I. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Lesk V. I. Okawa M. Ukawa A. Umeda T. Yoshié T.
- 出版者
- American Physical Society
- 雑誌
- Physical review D (ISSN:15507998)
- 巻号頁・発行日
- vol.70, no.7, pp.074503, 2004-10
- 被引用文献数
- 24 31
We extend the study of the light hadron spectrum and the quark mass in two-flavor QCD to smaller sea quark mass, corresponding to mPS/mV=0.60–0.35. Numerical simulations are carried out using the RG-improved gauge action and the meanfield-improved clover quark action at beta=1.8 (a=0.2 fm from rho meson mass). We observe that the light hadron spectrum for small sea quark mass does not follow the expectation from chiral extrapolations with quadratic functions made from the region of mPS/mV=0.80–0.55. Whereas fits with either polynomial or continuum chiral perturbation theory (ChPT) fail, the Wilson ChPT (WChPT) that includes a2 effects associated with explicit chiral symmetry breaking successfully fits the whole data: In particular, WChPT correctly predicts the light quark mass spectrum from simulations for medium heavy quark mass, such as mPS/mV>~0.5. Reanalyzing the previous data with the use of WChPT, we find the mean up and down quark mass being smaller than the previous result from quadratic chiral extrapolation by approximately 10%, mudMS-bar(µ=2 GeV)=3.11(17) [MeV] in the continuum limit.
- 著者
- Aoki S. Fukugita M. Hashimoto S. Ishikawa K.-I. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Okawa M. Tsutsui N. Ukawa A. Yamada N. Yoshié T.
- 出版者
- American Physical Society
- 雑誌
- Physical review D (ISSN:05562821)
- 巻号頁・発行日
- vol.69, no.9, pp.094512, 2004-05
- 被引用文献数
- 5
We present a lattice QCD calculation of the heavy quark expansion parameters µpi2 and µG2 for heavy-light mesons and heavy-light-light baryons. The calculation is carried out on a 203×48 lattice at beta=6.0 in the quenched approximation, using the lattice NRQCD action for heavy quarks. We obtain the parameters µpi2 and µG2 in two different methods: a direct calculation of the matrix elements and an indirect calculation through the mass spectrum, and confirm that both the methods give consistent results. We also discuss an application to the lifetime ratios.
- 著者
- Aoki S. Burkhalter R. Fukugita M. Hashimoto S. Ishikawa K.-I. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Okawa M. Onogi T. Tsutsui N. Ukawa A. Yamada N. Yoshié T.
- 出版者
- American Physical Society
- 雑誌
- Physical review D (ISSN:05562821)
- 巻号頁・発行日
- vol.68, no.5, pp.054502, 2003-09
- 被引用文献数
- 98 238
We present a high statistics study of the light hadron spectrum and quark masses in QCD with two flavors of dynamical quarks. Numerical simulations are carried out using the plaquette gauge action and the O(a)-improved Wilson quark action at β=5.2, where the lattice spacing is found to be a=0.0887(11) fm from the ρ meson mass, on a 203×48 lattice. At each of five sea quark masses corresponding to mPS/mV≃0.8–0.6, we generate 12 000 trajectories using a symmetrically preconditioned Hybrid Monte Carlo algorithm. Finite spatial volume effects are investigated employing 123×48, 163×48 lattices. We also perform a set of simulations in quenched QCD with the same lattice actions at a similar lattice spacing to those for the full QCD runs. In the meson sector we find clear evidence of sea quark effects. The J parameter increases for lighter sea quark masses, and the full QCD meson masses are systematically closer to experiment than in quenched QCD. Careful finite-size studies are made to ascertain that these are not due to finite-size effects. Evidence of sea quark effects is less clear in the baryon sector due to larger finite-size effects. We also calculate light quark masses and find mudMS̅ (2 GeV)=3.223(-0.069+0.046) MeV and msMS̅ (2 GeV)=84.5(-1.7+12.0) MeV which are about 20% smaller than in quenched QCD.
- 著者
- Umeda T. Aoki S. Fukugita M. Ishikawa K.-I. Ishizuka N. Iwasaki Y. Kanaya K. Kuramashi Y. Lesk V. I. Namekawa Y. Okawa M. 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.68, no.3, pp.034503, 2003-08
- 被引用文献数
- 15
We report on our study of two-flavor full QCD on anisotropic lattices using O(a)-improved Wilson quarks coupled with a renormalization-group-improved glue. The bare gauge and quark anisotropies corresponding to the renormalized anisotropy ξ=as/at=2 are determined as functions of β and κ, which cover the region of spatial lattice spacings as≈0.28–0.16 fm and mPS/mV≈0.6–0.9. The calibrations of the bare anisotropies are performed with the Wilson loop and the meson dispersion relation at four lattice cutoffs and 5–6 quark masses. Using the calibration results we calculate the meson mass spectrum and the Sommer scale r0. We confirm that the values of r0 calculated for the calibration using pseudoscalar and vector meson energy momentum dispersion relations coincide in the continuum limit within errors. This work serves to lay the groundwork for studies of heavy quark systems and the thermodynamics of QCD including the extraction of the equation of state in the continuum limit using Wilson-type quark actions.
- 著者
- Lesk V. I. Aoki S. Burkhalter R. Fukugita M. Ishikawa K.-I. Ishizuka N. Iwasaki Y. Kanaya K. Kuramashi Y. Okawa M. Taniguchi Y. Ukawa A. Umeda T. Yoshie T.
- 出版者
- American Physical Society
- 雑誌
- Physical review D (ISSN:05562821)
- 巻号頁・発行日
- vol.67, no.7, pp.074503, 2003-04
- 被引用文献数
- 16
We present results for the mass of the η′ meson in the continuum limit for two-flavor lattice QCD, calculated on the CP-PACS computer, using a renormalization-group-improved gauge action, and the Sheikoleslami-Wohlert fermion action with a tadpole-improved csw. The correlation functions are measured at three values of the coupling β corresponding to the lattice spacing a≈0.22, 0.16, 0.11 fm and for four values of the quark mass parameter κ corresponding to mπ/mρ≈0.8, 0.75, 0.7, 0.6. For each (β, κ) pair, 400–800 gauge configurations are used. The two-loop diagrams are evaluated using a noisy source method. We calculate η′ propagators using both smeared and local sources, and find that excited state contaminations are much reduced by smearing. A full analysis for the smeared propagators gives mη′=0.960(87)-0.248+0.036 GeV in the continuum limit, where the second error represents the systematic uncertainty coming from varying the functional form for chiral and continuum extrapolations.
- 著者
- Aoki S. Fukugita M. Hashimoto S. Ishikawa K.-I. Ishizuka N. Iwasaki Y. Kanaya K. Kaneko T. Kuramashi Y. Okawa M. Onogi T. Tominaga S. Tsutsui N. Ukawa A. Yamada N. Yoshie 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.114505, 2001-11
- 被引用文献数
- 34
We present a lattice QCD calculation of B→πlν semileptonic decay form factors in the small pion recoil momentum region. The calculation is performed on a quenched 163×48 lattice at β=5.9 with the nonrelativistic QCD action including the full 1/M terms. The form factors f1(v⋅kπ) and f2(v⋅kπ) defined in the heavy quark effective theory for which the heavy quark scaling is manifest are adopted, and we find that the 1/M correction to the scaling is small for the B meson. The dependence of the form factors on the light quark mass and on the recoil energy is found to be mild, and we use a global fit of the form factors at various quark masses and recoil energies to obtain model independent results for the physical differential decay rate. We find that the B* pole contribution dominates the form factor f+(q2) for small pion recoil energy, and obtain the differential decay rate integrated over the kinematic region q2>18 GeV2 to be