Hideaki Iida

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

Gluon-propagator functional form in the Landau gauge in SU(3) lattice QCD: Yukawa-type gluon propagator and anomalous gluon spectral function

P

Quark-Anti-Quark Potentials from Nambu-Bethe-Salpeter Amplitudes on Lattice

-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.

Gribov-Zwanziger action in SU(2) maximally Abelian gauge with U(1)

We study the gluon propagator D{sub {mu}}{sub {nu}}{sup ab}(x) in the Landau gauge in SU(3) lattice QCD at {beta}=5.7, 5.8, and 6.0 at the quenched level. The effective gluon mass is estimated as 400-600 MeV for r{identical_to}(x{sub {alpha}}x{sub {alpha}}){sup 1/2}=0.5-1.0 fm. Through the functional-form analysis of D{sub {mu}}{sub {nu}}{sup ab}(x) obtained in lattice QCD, we find that the Landau-gauge gluon propagator D{sub {mu}}{sub {mu}}{sup aa}(r) is well described by the Yukawa-type function e{sup -mr}/r with m{approx_equal}600 MeV for r=0.1-1.0 fm in the four-dimensional Euclidean space-time. In the momentum space, the gluon propagator D-tilde{sub {mu}}{sub {mu}}{sup aa}(p{sup 2}) with (p{sup 2}){sup 1/2}=0.5-3 GeV is found to be well approximated with a new-type propagator of (p{sup 2}+m{sup 2}){sup -3/2}, which corresponds to the four-dimensional Yukawa-type propagator. Associated with the Yukawa-type gluon propagator, we derive analytical expressions for the zero-spatial-momentum propagator D{sub 0}(t), the effective mass M{sub eff}(t), and the spectral function {rho}({omega}) of the gluon field. The mass parameter m turns out to be the effective gluon mass in the infrared region of {approx}1 fm. As a remarkable fact, the obtained gluon spectral function {rho}({omega}) is almost negative definite for {omega}>m, except for a positive {delta}-functional peak at {omega}=m.

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Quark--anti-quark (anti-q-q) potentials with finite quark masses are studied from the anti-q-q Nambu-Bethe-Salpeter (NBS) wave functions in quenched lattice QCD. With the use of a method which has been recently developed in the derivation of nuclear forces from lattice QCD, we derive the anti-q-q potentials from the NBS wave functions. We calculate the anti-q-q NBS wave functions in pseudo-scalar and vector channels for several quark masses. The derived potentials at each quark mass in both channels show linear plus Coulomb form. We also discuss the quark-mass and channel dependence of the anti-q-q potentials.

Landau gauge

We construct the local Gribov-Zwanziger action for SU(2) Euclidean Yang-Mills theories in the maximally Abelian (MA) gauge with U(1)

Tetraquark and Pentaquark Systems in Lattice QCD

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Entropy production in classical Yang-Mills theory from Glasma initial conditions

Landau gauge fixing based on the Zwanzigers work in the Landau gauge. By the restriction of the functional integral region to the Gribov region in the MA gauge, we give the nonlocal action. We localize the action with new fields and obtain the action with the shift of the new scalar fields, which has the terms, corresponding to the localized action of the horizon function in the MA gauge. The diagonal gluon propagator in the MA gauge at tree level behaves like the propagator from Gribov-Zwanziger action in the Landau gauge and shows the violation of Kallen-Lehmann representation.

Heavy-heavy-light quark potential in SU(3) lattice QCD

We study multi-quark systems in lattice QCD. First, we revisit and summarize our accurate mass measurements of low-lying 5Q states with J = 1/2 and I = 0 in both positive- and negative-parity channels in anisotropic lattice QCD. The lowest positive-parity 5Q state is found to have a large mass of about 2.24 GeV after the chiral extrapolation. To single out the compact 5Q state from NK scattering states, we use the hybrid boundary condition (HBC), and find no evidence of the compact 5Q state below 1.75 GeV in the negative-parity channel. Second, we study the multi-quark potential in lattice QCD to clarify the inter-quark interaction in multi-quark systems. The 5Q potential V5Q for the QQ- Q -QQ system is found to be well described by the “OGE Coulomb plus multi-Y Ansatz”: The sum of the one-gluon-exchange (OGE) Coulomb term and the multi-Y-type linear term based on the flux-tube picture. The 4Q potential V4Q for the QQ- QQ system is also described by the OGE Coulomb plus multi-Y Ansatz, when QQ and QQ are well separated. The 4Q system is described as a “two-meson” state with disconnected flux tubes, when the nearest quark and antiquark pair are spatially close. We observe a lattice-QCD evidence for the “flip-flop”, i.e., the fluxtube recombination between the connected 4Q state and the “two-meson” state. On the confinement mechanism, the lattice QCD results indicate the flux-tube-type linear confinement in multi-quark hadrons. Finally, we propose a proper quark-model Hamiltonian based on the lattice QCD results.

INTER-QUARK POTENTIALS IN BARYONS AND MULTI-QUARK SYSTEMS IN QCD

We study the thermalization process in classical Yang-Mills (CYM) field theory starting from noisy glasma-like initial conditions by investigating the initial-value sensitivity of trajectories. Kunihiro et al. linked entropy generation to the Kolmogorov-Sinai entropy, which gives the entropy production rate in classical chaotic systems, calculated numerically for CYM fields starting from purely random initial field configurations. In contrast, we here study glasma-like initial conditions. For small random fluctuations we obtain qualitatively similar results while no entropy increase is observed when such fluctuations are absent. We analyze the intermediate time Lyapunov spectrum for several time windows and calculate the Kolmogorov-Sinai entropy. We find a large number of positive Lyapunov exponents at the early stages of time evolution. Also for later times their number is a sizeable fraction of the total number of degrees of freedom. The spectrum of positive Lyapunov exponents at first changes rapidly, but then stabilizes, indicating that the dynamics of the gauge fields approaches a steady state. Thus we conclude that also for glasma-like initial conditions a significant amount of entropy is produced by classical gluon field dynamics.