Publications (10)0.88 Total impact
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ABSTRACT: We report on a study of 2+1 flavor lattice QCD with the $O(a)$improved Wilson quarks on a $16^3\times 32$ lattice at the lattice spacing $1/a\approx 2$GeV employing Luescher's domaindecomposed HMC(LDDHMC) algorithm. This is dedicated to a preliminary study for the PACSCS project which plans to complete the Wilsonclover $N_f=2+1$ program lowering the updown quark masses close to the physical values as much as possible. We focus on three issues: (i) how light quark masses we can reach with LDDHMC, (ii) efficiency of the algorithm compared with the conventional HMC, (iii) parameter choice for the production runs on PACSCS.11/2006;  [Show abstract] [Hide abstract]
ABSTRACT: Masses of the eta and etaprime mesons are estimated in Nf=2+1 lattice QCD with the nonperturbatively O(a) improved Wilson quark action and the Iwasaki RGimproved gluon action, using CPPACS/JLQCD configurations on a 16^3 x 32 lattice at beta=1.83 (lattice spacing is 0.122 fm). We apply a stochastic noise estimator technique combined with smearing method to evaluate correlators among flavor SU(2) singlet pseudoscalar operators and strange pseudoscalar operators for 10 combinations of up/down and strange quark masses. The correlator matrix is then diagonalized to identify signals for mass eigenstates. Masses of the ground state and the first excited state extrapolated to the physical point are m_eta= 0.545(16) GeV and m_etaprime= 0.871(46) GeV, being close to the experimental values of the eta and etaprime masses.11/2006; 
Article: An application of the UVfiltering preconditioner to the Polynomial Hybrid Monte Carlo algorithm
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ABSTRACT: We apply the UVfiltering preconditioner, previously used to improve the MultiBoson algorithm, to the Polynomial Hybrid Monte Carlo (UVPHMC) algorithm. The performance test for the algorithm is given for the plaquette gauge action and the $O(a)$improved Wilson action at $\beta=5.2, c_{\mathrm{sw}}=2.02, M_{\pi}/M_{\rho}\sim 0.8$ and 0.7 on a $16^3\times 48$ lattice. We find that the UVfiltering reduces the magnitude of the molecular dynamics force from the pseudo fermion by a factor 3 by tuning the UVfilter parameter. Combining with the multitime scale molecular dynamics integrator we achieve a factor 2 improvement. Comment: 7 pages, 1 figure, talk presented at Lattice2006 (Algorithm), PoS format; v2 references added10/2006; 
Article: The PACSCS Project
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ABSTRACT: We describe our plan to develop a largescale cluster system with a peak speed of 14.3Tflops for lattice QCD at the Center for Computational Sciences, University of Tsukuba, as a successor to the current 0.6Tflops CPPACS computer. The system consist of 2560 nodes connected by a 16x16x10 threedimensional hyper crossbar network. Each node has a single lowvoltage 2.8GHz Xeon processor and 2GBytes of memory with 6.4GBytes/sec bandwidth, and 160 GBytes of disk in RAID1 mode. The network link in each of the three directions is made of dual Gigabit Ethernet with the peak throughput of 250MByte/sec. Hence each node has an aggregate network bandwidth of 750MByte/sec. The system will run under Linux and SCore, and an extension of the PM driver is developed for the network. The system will be developed jointly with Hitachi Limited. The installation is scheduled in the first quarter of Japanese Fiscal 2006 (AprilJune 2006) and the start of operation is expected in July 2006.11/2005;  [Show abstract] [Hide abstract]
ABSTRACT: We consider 2+1 flavor Wilson Chiral Perturbation Theory including the lattice spacing contributions of O($a^{2}$). We adopt a power counting appropriate for the unquenched lattice simulations carried out by the CPPACS/JLQCD collaboration and compute the pseudo scalar meson masses to one loop. These expression are required to perform the chiral extrapolation of the CPPACS/JLQCD lattice data. Comment: 18 pagesPhysical review D: Particles and fields 09/2005;  [Show abstract] [Hide abstract]
ABSTRACT: CPPACS and JLQCD Collaborations are carrying out a joint project of the 2+1 flavor full QCD with the RGimproved gauge action and the nonperturbatively O(a)improved Wilson quark action. This simulation removes quenching effects of all three light quarks, which is the last major uncertainty in lattice QCD. In this report we present our results for the light meson spectrum and quark masses on a 203×40 lattice at the lattice spacing a≃0.10 fm.Nuclear Physics B  Proceedings Supplements 02/2005; 140:225227. · 0.88 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Renormalization constants (Zfactors ) of vector and axialvector currents are determined nonperturbatively in quenched QCD for a renormalization group improved gauge action and a tadpoleimproved clover quark action using the Schrödinger functional method. Nonperturbative values of Zfactors turn out to be smaller than 1loop perturbative values by O(15%) at a lattice spacing of a1[approximate] 1 GeV. The pseudoscalar and vector meson decay constants calculated with the nonperturbative Zfactors show a much better scaling behavior compared to previous results obtained with tadpoleimproved oneloop Zfactors. In particular, the nonperturbative Zfactors normalized at infinite physical volume show that the scaling violations of the decay constants are within about 10% up to the lattice spacing a1~1 GeV. The continuum estimates obtained from data in the range a1~ 1–2 GeV agree with those determined from finer lattices (a1~24 GeV) with the standard action.Physical review D: Particles and fields 01/2004;  [Show abstract] [Hide abstract]
ABSTRACT: We present a lattice QCD calculation of the parameters α and β which are necessary in the theoretical estimation of the proton lifetime in grand unified theories (GUTs) using chiral lagrangian approach. The simulation is carried out using the Wilson quark action at three gauge coupling constants in the quenched approximation. We obtain α(2GeV)=0.0091(08)(19+10)GeV3 and β(2GeV) = 0.0098(08) (20+10)GeV3 in the continuum limit where the first error is statistical and the second one is due to scale setting.10/2003;  [Show abstract] [Hide abstract]
ABSTRACT: We report on a calculation of the light hadron spectrum and quark masses in threeflavor dynamical QCD using the nonperturbatively O(a)improved Wilson quark action and a renormalizationgroup improved gauge action. Simulations are carried out on a 163 × 32 lattice at β = 1.9, where a−1 ≅ 2 GeV, with 6 ud quark masses corresponding to and 2 s quark masses close to the physical value. We observe that the inclusion of dynamical strange quark brings the lattice QCD meson spectrum to good agreement with experiment. Dynamical strange quarks also lead to a reduction of the uds quark masses by about 15%.Nuclear Physics B  Proceedings Supplements. 10/2003;  [Show abstract] [Hide abstract]
ABSTRACT: We present a detailed scaling study of the charm and bottom systems using our relativistic heavy quark action and the Iwasaki gauge action in quenched QCD. We investigate two cases: (i) all the four parameters ν, r s , c B , c E in the heavy quark action are determined up to oneloop level, and (ii) the parameter ν is nonperturbatively determined from the dispersion relation of the quarkonium with r s , c B , c E left at the oneloop level. We measure the charmonium and bottomonium spectra including both spinindependent and spindependent splittings, heavylight pseudoscalar decay constants and charm and bottom quark masses. The results for the bottom system show good scaling behavior compared to those with NRQCD. This feature is further improved, once the nonperturbative ν is employed.
Publication Stats
26  Citations  
0.88  Total Impact Points  
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Institutions

2004

University of Tsukuba
 Centre for Computational Sciences
Tsukuba, Ibarakiken, Japan
