arXiv subjects
Publications and source records attributed to T. Umeda.
We study relativistic charmonium on very fine quenched lattices (beta=6.4 and 6.6). We concentrate on the calculation of the hyperfine splitting between eta_c and J/psi, aiming for a controlled continuum extrapolation of this quantity. Results for the eta_c and J/psi wave functions are also presented.
We study hadron properties near the deconfining transition in the quenched lattice QCD simulation. This paper focuses on the heavy quarkonium states, such as $J/ψ$ meson. In order to treat heavy quarks at $T>0$, we adopt the $O(a)$ improved Wilson action on anisotropic lattice. We discuss $c\bar{c}$ bound state observing the wave function and compare the meson correlators at above and below $T_c$. Although we find a large change of correlator near the $T_c$, the strong spatial correlation which is almost the same as confinement phase survives even $T\sim 1.5T_c$.
We study the response of meson masses to the chemical potential ($\partial{m}/\partialμ$) at high temperature and at zero chemical potential on $N_f=2$ lattice with staggered fermions. Preliminary results for the meson composed of different quarks show that $\partial{m}/\partialμ|_{μ=0}$ is negative in the confinement phase and positive in the deconfinement phase.
We study hadron properties near the deconfining transition in the finite temperature lattice QCD. This paper focus on the heavy quarkonium states, such as $J/ψ$ meson. We compare the meson correlators above and below $T_c$ and discuss the possibility of the $c\bar{c}$ bound state by observing the wave function.
We study the static three quark potential using lattice QCD simulation. At zero temperature, the three quark potential is extracted from the baryonic Wilson loop and fitted to the phenomenological form, the sum of the Coulomb term, linearly rising term and the constant. We compare two types of the linear term, ``$Y$'' and ``$Δ$'' type, and find that the string tension almost coincide with $σ_{Q\bar{Q}}$ in the former case. We also investigate the three quark potential at finite temperature using the Polyakov loop correlation. In the deconfined phase, the screened potential is observed similarly to the case of $Q\bar{Q}$ system.
We analyze temporal and spatial meson correlators in quenched lattice QCD at T>0. Below T_c we observe little change in the meson properties as compared with T=0. Above T_c we observe new features: chiral symmetry restoration and signals of plasma formation, but also indication of persisting mesonic (metastable) states and different temporal and spatial masses in the mesonic channels. This suggests a complex picture of QGP in the region 1 - 1.5 T_c.
We study the response of hadron masses with respect to chemical potential at $μ=0$. Our preliminary results of the pion channel show that $\partial m/\partial μ$ in the confinement phase is significantly larger than that in the deconfinement phase, which is consistent with the chiral restoration.
We present results for mesonic propagators in temporal and spatial directions at T below and above the deconfining transition in quenched QCD. Anisotropic lattices are used to get enough information in the temporal direction. We use the Wilson fermion action for light quarks and Fermilab action for heavy quarks.
We report our results of the Monte Carlo Renormalization Group analysis in two dimensional coupling space. The qualitative features of the RG flow are described with a phenomenological RG equation. The dependence on the lattice spacing for various actions provides the conditions to determine the parameters entering the RG equation.
We analyze temporal and spatial meson correlators in quenched lattice QCD at T>0. Above T_c we find different masses and (spatial) screening masses, signals of plasma formation, and indication of persisting mesonic excitations.
We study the effects of the chemical potential on the $ρ$ meson mass at finite temperature. Our preliminary results show that some effects are seen in the vicinity of the phase transition point. Although the signal is still too noisy to obtain conclusive physical results within limited statistics, the mass susceptibility is consistent with zero.
We present results for mesonic propagators in temporal and spatial direction and for topological properties at T below and above the deconfining transition in quenched QCD. We use anisotropic lattices and Wilson fermions.
We have explored the behaviour of some improved actions based on a nonperturbative renormalization group (RG) analysis in coupling space. We calculate the RG flow in two-coupling space $(\boneone,\bonetwo)$ and examine the restoration of rotational invariance and the scaling of physical quantities $(T_c/\sqrtσ)$.