132 research outputs found
Temporal meson correlators at finite temperature on quenched anisotropic lattice
We study charmonium correlators at finite temperature in quenched anisotropic
lattice QCD. The smearing technique is applied to enhance the low energy part
of the correlator. We use two analysis procedures: the maximum entropy method
for extraction of the spectral function without assuming specific form, as an
estimate of the shape of spectral function, and the fit assuming
typical forms as quantitative evaluation of the parameters associated to the
forms. We find that at the ground state peak has almost the
same mass as at T=0 and almost vanishing width. At , our result
suggests that the correlator still has nontrivial peak structure at almost the
same position as below with finite width.Comment: Lattice 2002 Nonzero temperature 3page
SU(3) lattice QCD study for octet and decuplet baryon spectra
The spectra of octet and decuplet baryons are studied using SU(3) lattice QCD
at the quenched level. As an implementation to reduce the statistical
fluctuation, we employ the anisotropic lattice with improved quark
action. In relation to , we measure also the mass of the SU(3)
flavor-singlet negative-parity baryon, which is described as a three quark
state in the quenched lattice QCD, and its lowest mass is measured about 1.6
GeV. Since the experimentally observed negative-parity baryon
is much lighter than 1.6 GeV, may include a large component of
a bound state rather than the three quark state. The mass splitting
between the octet and the decuplet baryons are also discussed in terms of the
current quark mass.Comment: 8 pages, 3 figures, proceeding of "International Symposium on Hadron
and Nuclei" at Yonsei Univ., Seoul, Korea 20-22 Feb. 200
Heavy-light meson in anisotropic lattice QCD
We examine whether the improved quark action on anisotropic lattices
can be used as a framework for the heavy quark, which enables precision
computation of matrix elements of heavy-light mesons. To this end, it is
crucial to verify that a mass independent and nonperturbative tuning of the
parameters is possible. As a first step, we observe the dispersion relation of
heavy-light mesons on a quenched lattice using the action which is
nonperturbatively tuned only for the leading terms. On a lattice with the
spatial cutoff 1.6 GeV and the anisotropy , the
relativity relation holds within 2% accuracy in the quark mass region with the bare anisotropy parameter tuned for the massless quark.
We also apply the action to a calculation of heavy-light decay constants in the
charm quark mass region.Comment: Lattice2002(heavyquark), 3 pages, 2 figure
Negative-Parity Baryons in Quenched Anisotropic Lattice QCD
We study negative-parity baryon spectra in quenched anisotropic lattice QCD.
The negative-parity baryons are measured as the parity partner of the
ground-state baryons. In addition to the flavor octet and decuplet baryons, we
pay much attention to the flavor-singlet negative-parity baryon as a
three-quark state and compare it with the Lambda(1405) baryon. Numerical
results of the flavor octet and decuplet negative-parity baryon masses are
close to experimental values of lowest-lying negative-parity baryons, while the
flavor-singlet baryon is much heavier than Lambda(1405). This indicates that
the Lambda(1405) would be a multi-quark state such as the N-Kbar molecule
rather than the flavor-singlet 3 quark state.Comment: 4 pages, 4 figs. Talk given at 16th International Conference on
Particles and Nuclei (PANIC 02), Osaka, Japan, 30 Sep - 4 Oct 200
Charmonium properties in deconfinement phase in anisotropic lattice QCD
J/Psi and eta_c above the QCD critical temperature T_c are studied in
anisotropic quenched lattice QCD, considering whether the c\bar c systems above
T_c are spatially compact (quasi-)bound states or scattering states. We adopt
the standard Wilson gauge action and O(a)-improved Wilson quark action with
renormalized anisotropy a_s/a_t =4.0 at \beta=6.10 on 16^3\times (14-26)
lattices, which correspond to the spatial lattice volume V\equiv
L^3\simeq(1.55{\rm fm})^3 and temperatures T\simeq(1.11-2.07)T_c. We
investigate the c\bar c system above T_c from the temporal correlators with
spatially-extended operators, where the overlap with the ground state is
enhanced. To clarify whether compact charmonia survive in the deconfinement
phase, we investigate spatial boundary-condition dependence of the energy of
c\bar c systems above T_c. In fact, for low-lying S-wave c \bar c scattering
states, it is expected that there appears a significant energy difference
\Delta E \equiv E{\rm (APBC)}-E{\rm (PBC)}\simeq2\sqrt{m_c^2+3\pi^2/L^2}-2m_c
(m_c: charm quark mass) between periodic and anti-periodic boundary conditions
on the finite-volume lattice. In contrast, for compact charmonia, there is no
significant energy difference between periodic and anti-periodic boundary
conditions. As a lattice QCD result, almost no spatial boundary-condition
dependence is observed for the energy of the c\bar c system in J/\Psi and
\eta_c channels for T\simeq(1.11-2.07)T_c. This fact indicates that J/\Psi and
\eta_c would survive as spatially compact c\bar c (quasi-)bound states below
2T_c. We also investigate a -wave channel at high temperature with maximally
entropy method (MEM) and find no low-lying peak structure corresponding to
\chi_{c1} at 1.62T_c.Comment: 13 pages, 11 figure
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