864 research outputs found
A Remark on the Large Difference between the Glueball Mass and T(C) in Quenched QCD
The lattice QCD studies indicate that the critical temperature MeV of the deconfinement phase transition in quenched QCD is
considerably smaller than the lowest-lying glueball mass MeV, i.e., . As a consequence of this large
difference, the thermal excitation of the glueball in the confinement phase is
strongly suppressed by the statistical factor as even near . We consider its physical implication, and
argue the abnormal feature of the deconfinement phase transition in quenched
QCD from the statistical viewpoint. To appreciate this, we demonstrate a
statistical argument of the QCD phase transition using the recent lattice QCD
data. From the phenomenological relation among and the glueball mass, the
deconfinement transition is found to take place in quenched QCD before a
reasonable amount of glueballs is thermally excited. In this way, quenched QCD
reveals a question ``what is the trigger of the deconfinement phase transition
?''Comment: 6 pages, 4 figure
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
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
Spin 3/2 Penta-quarks in anisotropic lattice QCD
A high-precision mass measurement for the pentaquark (5Q) Theta^+ in
J^P=3/2^{\pm} channel is performed in anisotropic quenched lattice QCD using a
large number of gauge configurations as N_{conf}=1000. We employ the standard
Wilson gauge action at beta=5.75 and the O(a) improved Wilson (clover) quark
action with kappa=0.1210(0.0010)0.1240 on a 12^3 \times 96 lattice with the
renormalized anisotropy as a_s/a_t = 4. The Rarita-Schwinger formalism is
adopted for the interpolating fields. Several types of the interpolating fields
with isospin I=0 are examined such as (a) the NK^*-type, (b) the
(color-)twisted NK^*-type, (c) a diquark-type. The chiral extrapolation leads
to only massive states, i.e., m_{5Q} \simeq 2.1-2.2 GeV in J^P=3/2^- channel,
and m_{5Q} = 2.4-2.6 GeV in J^P=3/2^+ channel. The analysis with the hybrid
boundary condition(HBC) is performed to investigate whether these states are
compact 5Q resonances or not. No low-lying compact 5Q resonance states are
found below 2.1GeV.Comment: 15 pages, 6 figures, 4 table
Survival of charmonia above Tc in anisotropic lattice QCD
We find a strong evidence for the survival of and as
spatially-localized (quasi-)bound states above the QCD critical
temperature , by investigating the boundary-condition dependence of their
energies and spectral functions. In a finite-volume box, there arises a
boundary-condition dependence for spatially spread states, while no such
dependence appears for spatially compact states. In lattice QCD, we find almost
{\it no} spatial boundary-condition dependence for the energy of the
system in and channels for . We also
investigate the spectral function of charmonia above in lattice QCD using
the maximum entropy method (MEM) in terms of the boundary-condition dependence.
There is {\it no} spatial boundary-condition dependence for the low-lying peaks
corresponding to and around 3GeV at . These facts
indicate the survival of and as compact
(quasi-)bound states for .Comment: 4 pages, 1 figur
The System of Multi Color-flux-tubes in the Dual Ginzburg-Landau Theory
We study the system of multi color-flux-tubes in terms of the dual Ginzburg
-Landau theory. We consider two ideal cases, where the directions of all the
color-flux-tubes are the same in one case and alternative in the other case for
neighboring flux-tubes. We formulate the system of multi color-flux -tubes by
regarding it as the system of two color-flux-tubes penetrating through a two
dimensional sphere surface. We find the multi flux-tube configuration becomes
uniform above some critical flux-tube number density . On the other hand, the inhomogeneity on the color electric
distribution appears when the flux-tube density is smaller than . We
discuss the relation between the inhomogeneity in the color-electric
distribution and the flux-tube number density in the multi-flux-tube system
created during the QGP formation process in the ultra-relativistic heavy-ion
collision.Comment: 17 pages, Revtex, ( 7 figures - available on request from
[email protected]
Anisotropic Lattice QCD Studies of Penta-quark Anti-decuplet
Anti-decuplet penta-quark baryon is studied with the quenched anisotropic
lattice QCD for accurate measurement of the correlator. Both the positive and
negative parity states are studied using a non-NK type interpolating field with
I=0 and J=1/2. After the chiral extrapolation, the lowest positive parity state
is found at m_{Theta} \simeq 2.25 GeV, which is too massive to be identified
with the experimentally observed Theta^+(1540). The lowest negative parity
state is found at m_{Theta}\simeq 1.75 GeV, which is rather close to the
empirical value. To confirm that this state is a compact 5Q resonance, a new
method with ``hybrid boundary condition (HBC)'' is proposed. The HBC analysis
shows that the observed state in the negative parity channel is an NK
scattering state.Comment: A talk given at International Workshop PENTAQUARK04, July 20-23, 2004
at SPring-8, Japan, 8 pages, 7 figures, 2 table
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