Motoo Sekiguchi

Lattice study of low-lying nonet scalar mesons in quenched approximation

Abstract Using lattice QCD simulation in the quenched approximation, we study the κ meson, which is P 0 3 in the quark model, and compare experimental and other lattice data. The κ is the lowest scalar meson with strangeness and constitutes the scalar nonet. The obtained mass is much higher than the recent experimental value, and therefore the κ ( 800 ) is difficult to consider as a simple two-body constituent-quark structure, and may have another unconventional structure.

Lattice QCD study of four-quark components of the isosinglet scalar mesons: Significance of disconnected diagrams

We study the possible significance of four-quark states in the isosinglet scalar mesons (JPC=0++, I=0) by performing two-flavor full lattice QCD simulations on an 83×16 lattice using the improved gauge action and the clover-improved Wilson quark action. In particular, we evaluate the propagators of molecular and tetraquark operators together with singly disconnected diagrams. In the computation of the singly disconnected diagrams we employ the Z2-noise method with the truncated eigenmode approach. We show that the quark loops given by the disconnected diagrams play an essential role in propagators of tetraquark and molecular operators.

Lattice Lattice study of “f0 (600) or σ”

We investigate the propagator of “f0 (600) or the σ” by the full-QCD simulation with Wilson fermions. We calculate the mesonic correlator in theI = 0, JP = 0+ channel on the 83 × 16 lattice. Plaquet action and Wilson fermion action are adopted. A coupling constant β is set to 4.8 and three kinds of hopping parameter,κ = 0.1846 0.1874 and 0.1891 are assayed. The disconnected diagram in the propagator is evaluated through taking average over 500 or 1000 Z2 noise. Simulations with the larger hopping parameter provide us with less noisy results. Though the statistics is not yet enough, our results indicate the existence of a pole with a mass in almost the same order as that of the π.

The Low-lying Scalar Mesons and Related Topics

After presenting the motivations to explore the low-lying scalar mesons such as the

Mass Spectra and Wave Functions of Meson Systems and the Covariant Oscillator Quark Model as an Expansion Basis

\sigma

I = 0 scalar channel

,

Lattice study of the κ meson

a_0

Meson spectra and wave functions in a covariant version of the linear-plus-Coulomb potential quark model

and

Possible Effects of a Composite Iso-Scalar Weak Boson in a Left-Right Symmetric Preon Model

\kappa

Scalar mesons in lattice QCD

in the unquenched as well as quenched lattice QCD, we review the works done by our collaboration (SCALAR Collaboration) with a what-to-do-next list. We briefly mention the imporatance to explore the