495 research outputs found
Status of the CP-PACS Project
The CP-PACS computer with a peak speed of 300 Gflops was completed in March
1996 and has started to operate. We describe the final specification and the
hardware implementation of the CP-PACS computer, and its performance for QCD
codes. A plan of the grade-up of the computer scheduled for fall of 1996 is
also given.Comment: Talk presented at LATTICE96(machines), 3 pages including 5 PS figure
Two-Nucleon Bound States in Quenched Lattice QCD
We address the issue of bound state in the two-nucleon system in lattice QCD.
Our study is made in the quenched approximation at the lattice spacing of a =
0.128 fm with a heavy quark mass corresponding to m_pi = 0.8 GeV. To
distinguish a bound state from an attractive scattering state, we investigate
the volume dependence of the energy difference between the ground state and the
free two-nucleon state by changing the spatial extent of the lattice from 3.1
fm to 12.3 fm. A finite energy difference left in the infinite spatial volume
limit leads us to the conclusion that the measured ground states for not only
spin triplet but also singlet channels are bounded. Furthermore the existence
of the bound state is confirmed by investigating the properties of the energy
for the first excited state obtained by 2x2 diagonalization method. The
scattering lengths for both channels are evaluated by applying the finite
volume formula derived by Luscher to the energy of the first excited states.Comment: 34 pages, 28 figure
An Exploratory Study of Nucleon-Nucleon Scattering Lengths in Lattice QCD
An exploratory study is made of the nucleon-nucleon -wave scattering
lengths in quenched lattice QCD with the Wilson quark action. The - and
- scattering lengths are also calculated for comparison. The
calculations are made with heavy quarks corresponding to . The results show that the - system has an attractive force in
both spin-singlet and triplet channels, with their scattering lengths
significantly larger than those for the - and - cases, a
trend which is qualitatively consistent with the experiment. Problems toward a
more realistic calculation for light quarks are discussed.Comment: 9 pages. Latex file. Figures are also included as ps file
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 (=8, 12 and 16) lattices at the quark mass of
and 0.01. We find a phase transition to be absent for
, and also quite likely at . The quark mass dependence
of susceptibilities is consistent with a second-order transition at .
The exponents, however, deviate from the O(2) and O(4) values theoretically
expected.Comment: 3 pages, Latex(espcrc2,epsf), 3 ps figures, Poster presented at
Lattice 9
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 . This method leads to a remarkable
improvement of scaling behavior of the light quark masses compared to the
conventional method. We obtain MeV for the averaged up and
down quark mass and MeV for the strange quark mass in the
{\barMS} scheme at GeV.Comment: 3 pages, latex source-file, 2 figures as epsf-file, uses espcrc2.sty.
Poster presented at Lattice 97: 15th International Symposium on Lattice Field
Theory, Edinburgh, Scotland, 22-26 Jul 199
The end point of the first-order phase transition of the SU(2) gauge-Higgs model on a four-dimensional isotropic lattice
We report results of a study of the end point of the electroweak phase
transition of the SU(2) gauge-Higgs model defined on a four-dimensional
isotropic lattice with N_t=2. Finite-size scaling study of Lee-Yang zeros
yields lambda_c=0.00116(16) for the end point. Combined with a zero-temperature
measurement of Higgs and W boson masses, this leads to M_{H,c}=68.2+-6.6 GeV
for the critical Higgs boson mass. An independent analysis of Binder cumulant
gives a consistent value lambda_c=0.00102(3) for the end point.Comment: LATTICE98(electroweak), 3 pages of LaTeX, 4 figure
Light quark masses from unquenched lattice QCD
We calculate the light meson spectrum and the light quark masses by lattice
QCD simulation, treating all light quarks dynamically and employing the Iwasaki
gluon action and the nonperturbatively O(a)-improved Wilson quark action. The
calculations are made at the squared lattice spacings at an equal distance
a^2~0.005, 0.01 and 0.015 fm^2, and the continuum limit is taken assuming an
O(a^2) discretization error. The light meson spectrum is consistent with
experiment. The up, down and strange quark masses in the \bar{MS} scheme at 2
GeV are \bar{m}=(m_{u}+m_{d})/2=3.55^{+0.65}_{-0.28} MeV and
m_s=90.1^{+17.2}_{-6.1} MeV where the error includes statistical and all
systematic errors added in quadrature. These values contain the previous
estimates obtained with the dynamical u and d quarks within the error.Comment: 4 pages, 3 figures, revtex4; v2: contents partly modified, published
versio
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