arXiv subjects

Toru T. Takahashi

Publications and source records attributed to Toru T. Takahashi.

44 records · Page 3Linked to original sources

arXiv2004

Lattice QCD Study for the Interquark Force in Three-Quark and Multi-Quark Systems

We study the three-quark and multi-quark potentials in SU(3) lattice QCD. From the accurate calculation for more than 300 different patterns of 3Q systems, the static ground-state 3Q potential $V_{\rm 3Q}^{\rm g.s.}$ is found to be well described by the Coulomb plus Y-type linear potential (Y-Ansatz) within 1%-level deviation. As a clear evidence for Y-Ansatz, Y-type flux-tube formation is actually observed on the lattice in maximally-Abelian projected QCD. For about 100 patterns of 3Q systems, we perform the accurate calculation for the 1st excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$ by diagonalizing the QCD Hamiltonian in the presence of three quarks, and find a large gluonic-excitation energy $ΔE_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}$ of about 1 GeV, which gives a physical reason of the success of the quark model. $ΔE_{\rm 3Q}$ is found to be reproduced by the ``inverse Mercedes Ansatz'', which indicates a complicated bulk excitation for the gluonic-excitation mode. We study also the tetra-quark and the penta-quark potentials in lattice QCD, and find that they are well described by the OGE Coulomb plus multi-Y type linear potential, which supports the flux-tube picture even for the multi-quarks. Finally, the narrow decay width of penta-quark baryons is discussed in terms of the QCD string theory.

hep-lat↗

arXiv2004

Narrow Width of Penta-Quark Baryons in QCD String Theory

Using the QCD string theory, we investigate the physical reason of the narrow width of penta-quark baryons in terms of the large gluonic-excitation energy. In the QCD string theory, the penta-quark baryon decays via a gluonic-excited state of a baryon and meson system, where a pair of Y-shaped junction and anti-junction is created. On the other hand, we find in lattice QCD that the lowest gluonic-excitation energy takes a large value of about 1 GeV. Therefore, in the QCD string theory, the decay of the penta-quark baryon near the threshold is considered as a quantum tunneling process via a highly-excited state (a gluonic-excited state), which leads to an extremely narrow decay width of the penta-quark system.

hep-ph↗

arXiv2004

The Static Penta-quark Potential in Lattice QCD

We perform the first study for the static penta-quark (5Q) potential in lattice QCD with $β$=6.0 and $16^3 \times 32$ at the quenched level. Accurate results of the 5Q potential are extracted from the 5Q Wilson loop using the smearing method, which enhances the ground-state component. The tetra-quark potential for the $\rm QQ$-$\rm {\bar Q}{\bar Q}$ system is also studied in lattice QCD. The multi-quark potentials are found to be well described as a sum of the one-gluon-exchange Coulomb term and the multi-Y linear confinement term based on the flux-tube picture.

hep-lat↗

arXiv2004

Study of Quark Confinement in Baryons with Lattice QCD

In SU(3) lattice QCD, we perform the detailed study for the ground-state three-quark (3Q) potential $V_{\rm 3Q}^{\rm g.s.}$ and the 1st excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$, i.e., the energies of the ground state and the 1st excited state of the gluon field in the presence of the static three quarks. From the accurate calculation for more than 300 different patterns of 3Q systems, the static ground-state 3Q potential $V_{\rm 3Q}^{\rm g.s.}$ is found to be well described by the Coulomb plus Y-type linear potential (Y-Ansatz) within 1%-level deviation. As a clear evidence for Y-Ansatz, Y-type flux-tube formation is actually observed on the lattice in maximally-Abelian projected QCD. For about 100 patterns of 3Q systems, we calculate the 1st excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$, and find a large gluonic-excitation energy $ΔE_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}$ of about 1 GeV, which gives a physical reason of the success of the quark model even without gluonic excitations. We present also the first study for the penta-quark potential $V_{\rm 5Q}$ in lattice QCD, and find that $V_{\rm 5Q}$ is well described by the sum of the OGE Coulomb plus multi-Y type linear potential.

hep-lat↗

arXiv2004

Y-type Flux-Tube Formation and Gluonic Excitations in Baryons: From QCD to Quark Model

Using SU(3) lattice QCD, we perform the first systematic study for the ground-state three-quark (3Q) potential $V_{\rm 3Q}^{\rm g.s.}$ and the 1st excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$, {\it i.e.}, the energies of the ground state and the 1st excited state of the gluon field in the presence of the static three quarks. From the accurate and thorough calculation for more than 300 different patterns of 3Q systems, the static ground-state 3Q potential $V_{\rm 3Q}^{\rm g.s.}$ is found to be well described by the Coulomb plus Y-type linear potential, {\it i.e.}, Y-Ansatz, within 1%-level deviation. As a clear evidence for Y-Ansatz, Y-type flux-tube formation is actually observed on the lattice in maximally-Abelian projected QCD. For more than 100 patterns of 3Q systems, we calculate the 1st excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$ in quenched lattice QCD, and find the gluonic excitation energy $ΔE_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}$ to be about 1 GeV. This large gluonic-excitation energy is conjectured to ensure the success of the quark model for the low-lying hadrons even without gluonic excitations.

hep-lat↗

arXiv2004

First Study for the Pentaquark Potential in SU(3) Lattice QCD

The static penta-quark (5Q) potential $V_{\rm 5Q}$ is studied in SU(3) lattice QCD with $16^3\times 32$ and $β$=6.0 at the quenched level. From the 5Q Wilson loop, $V_{\rm 5Q}$ is calculated in a gauge-invariant manner, with the smearing method to enhance the ground-state component. $V_{\rm 5Q}$ is well described by the OGE plus multi-Y Ansatz: a sum of the OGE Coulomb term and the multi-Y-type linear term proportional to the minimal total length of the flux-tube linking the five quarks. Comparing with ${\rm Q \bar Q}$ and 3Q potentials, we find a universality of the string tension, $σ_{\rm Q \bar Q} \simeq σ_{\rm 3Q} \simeq σ_{\rm 5Q}$, and the OGE result for Coulomb coefficients.

hep-lat↗

arXiv2004

Y-type Flux-Tube Formation in Baryons

For more than 300 different patterns of the 3Q systems, the ground-state 3Q potential $V_{\rm 3Q}^{\rm g.s.}$ is investigated using SU(3) lattice QCD with $12^3\times 24$ at $β=5.7$ and $16^3\times 32$ at $β=5.8, 6.0$ at the quenched level. As a result of the detailed analyses, we find that the ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ is well described with so-called Y-ansatz as $V_{\rm 3Q}=-A_{\rm 3Q}\sum_{i<j}\frac1{|{\bf r}_i-{\bf r}_j|} +σ_{\rm 3Q} L_{\rm min}+C_{\rm 3Q}$, with the accuracy better than 1%. Here, $L_{\rm min}$ denotes the minimal value of total flux-tube length. We also studythe excited-state potential $V_{\rm 3Q}^{\rm e.s.}$ using lattice QCD with $16^3\times 32$ at $β=5.8, 6.0$ for more than 100 patterns of the 3Q systems. The energy gap between $V_{\rm 3Q}^{\rm g.s.}$ and $V_{\rm 3Q}^{\rm e.s.}$, which physically means the gluonic excitation energy, is found to be about 1 GeV in the typical hadronic scale. Finally, we suggest a possible scenario which connects the success of the quark model to QCD.

hep-lat↗

arXiv2002

The gluonic excitation of the three-quark system in SU(3) lattice QCD

We present the first study of the gluonic excitation in the three-quark (3Q) system in SU(3) lattice QCD with $β$=5.8 and $16^3 \times 32 $ at the quenched level. For the spatially-fixed 3Q system, we measure the gluonic excited-state potential, which corresponds to the flux-tube vibrational energy in the flux-tube picture. The lowest gluonic-excitation energy in the 3Q system is found to be about 1GeV in the hadronic scale. This large gluonic-excitation energy is expected to bring about the success of the simple quark model without gluonic modes.

hep-lat↗