arXiv subjects

T. T. Takahashi

Publications and source records attributed to T. T. Takahashi.

33 records · Page 2Linked to original sources

arXiv2004

Lattice QCD Study of the Pentaquark Baryons

We study the spin $\frac12$ hadronic state in quenched lattice QCD to search for a possible $S=+1$ pentaquark resonance. Simulations are carried out on $8^3\times 24$, $10^3\times 24$, $12^3\times 24$ and $16^3\times 24$ lattices at $β$=5.7 at the quenched level with the standard plaquette gauge action and Wilson quark action. We adopt two independent operators with I=0 and $J^P=\frac12$ to construct a $2\times 2$ correlation matrix. After the diagonalization of the correlation matrix, we successfully obtain the energies of the ground-state and the 1st excited-state in this channel. The volume dependence of the energies suggests the existence of a possible resonance state slightly above the NK threshold in I=0 and $J^P=\frac12^-$ channel.

hep-lat↗

arXiv2004

Detailed analysis of the gluonic excitation in the three-quark system in lattice QCD

We study the excited-state potential and the gluonic excitation in the static three-quark (3Q) system using SU(3) lattice QCD with $16^3\times 32$ at $β$=5.8 and 6.0 at the quenched level. For about 100 different patterns of spatially-fixed 3Q systems, we accurately extract the excited-state potential $V_{\rm 3Q}^{\rm e.s.}$ together with the ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ by diagonalizing the QCD Hamiltonian in the presence of three quarks. The gluonic excitation energy $ΔE_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}$ is found to be about 1 GeV at the typical hadronic scale. This large gluonic-excitation energy is conjectured to give a physical reason of the success of the quark model for low-lying hadrons even without explicit gluonic modes. We investigate the functional form of $ΔE_{\rm 3Q}$ in terms of the 3Q location. The lattice data of $ΔE_{\rm 3Q}$ are relatively well reproduced by the ``inverse Mercedes Ansatz'' with the ``modified Y-type flux-tube length'', which indicates that the gluonic-excitation mode is realized as a complicated bulk excitation of the whole 3Q system.

hep-lat↗

arXiv2004

Quark Confinement Physics from Lattice QCD

We study quark confinement physics using lattice QCD. In the maximally abelian (MA) gauge, the off-diagonal gluon amplitude is strongly suppressed, and then the off-diagonal gluon phase shows strong randomness, which leads to a large effective off-diagonal gluon mass, M_off=1.2GeV. Due to the large off-diagonal gluon mass in the MA gauge, low-energy QCD is abelianized like nonabelian Higgs theories. In the MA gauge, there appears a macroscopic network of the monopole world-line covering the whole system. We extract and analyze the dual gluon field B_mu from the monopole-current system in the MA gauge, and evaluate the dual gluon mass as m_B = 0.4-0.5GeV in the infrared region, which is a lattice-QCD evidence of the dual Higgs mechanism by monopole condensation. Even without explicit use of gauge fixing, we can define the maximal abelian projection by introducing a ``gluonic Higgs field'' phi(x), whose hedgehog singularities lead to monopoles. From infrared abelian dominance and infrared monopole condensation, infrared QCD is describable with the dual Ginzburg-Landau theory. In relation to the color-flux-tube picture for baryons, we study the three-quark (3Q) ground-state potential V_3Q in SU(3) lattice QCD at the quenched level, with the smearing technique for enhancement of the ground-state component. With accuracy better than a few %, V_3Q is well described by a sum of the two-body Coulomb part and the three-body linear confinement part sigma_3Q L_min, where L_min denotes the minimal value of the total length of the color flux tube linking the three quarks. Comparing with the Q-barQ potential, we find a universal feature of the string tension and the OGE result for the Coulomb coefficient.

hep-lat↗

arXiv2004

Hadron Physics and Confinement Physics in Lattice QCD

We are aiming to construct Quark Hadron Physics and Confinement Physics based on QCD. Using SU(3)$_c$ lattice QCD, we are investigating the three-quark potential at T=0 and $T \ne 0$, mass spectra of positive and negative-parity baryons in the octet and the decuplet representations of the SU(3) flavor, glueball properties at T=0 and $T \ne 0$. We study also Confinement Physics using lattice QCD. In the maximally abelian (MA) gauge, the off-diagonal gluon amplitude is strongly suppressed, and then the off-diagonal gluon phase shows strong randomness, which leads to a large effective off-diagonal gluon mass, $M_{\rm off} \simeq 1.2 {\rm GeV}$. Due to the large off-diagonal gluon mass in the MA gauge, infrared QCD is abelianized like nonabelian Higgs theories. In the MA gauge, there appears a macroscopic network of the monopole world-line covering the whole system. From the monopole current, we extract the dual gluon field $B_μ$, and examine the longitudinal magnetic screening. We obtain $m_B \simeq$ 0.5 GeV in the infrared region, which indicates the dual Higgs mechanism by monopole condensation. From infrared abelian dominance and infrared monopole condensation, low-energy QCD in the MA gauge is described with the dual Ginzburg-Landau (DGL) theory.

hep-ph↗

arXiv2004

Strong randomness of off-diagonal gluon phases and off-diagonal gluon mass in the maximally abelian gauge in QCD

We study abelianization of QCD in the maximally abelian (MA) gauge. In the MA gauge, the off-diagonal gluon amplitude is strongly suppressed, and then the off-diagonal gluon phase shows strong randomness, which leads to a large off-diagonal gluon mass. Using lattice QCD, we find a large effective off-diagonal gluon mass in the MA gauge: $M_{\rm off} \simeq 1.2 {\rm GeV}$ in SU(2) QCD, $M_{\rm off} \simeq 1.1 {\rm GeV}$ in SU(3) QCD. Due to the large off-diagonal gluon mass in the MA gauge, infrared QCD is well abelianized like nonabelian Higgs theories. We investigate the inter-monopole potential and the dual gluon field $B_μ$ in the MA gauge, and find longitudinal magnetic screening with $m_B \simeq$ 0.5 GeV in the infrared region, which indicates the dual Higgs mechanism by monopole condensation. We propose a gauge invariant description of the MA projection by introducing the ``gluonic Higgs scalar field''.

hep-lat↗

arXiv2004

Possible Hadronic Molecule Lambda(1405) and Thermal Glueballs in SU(3) Lattice QCD

We aim to construct quark hadron physics based on QCD. First, using lattice QCD, we study mass spectra of positive-parity and negative-parity baryons in the octet, the decuplet and the singlet representations of the SU(3) flavor. In particular, we consider the lightest negative-parity baryon, the $Λ$(1405), which can be an exotic hadron as the $N \bar K$ molecular state or the flavor-singlet three-quark state. We investigate the negative-parity flavor-singlet three-quark state in lattice QCD using the quenched approximation, where the dynamical quark-anitiquark pair creation is absent and no mixing occurs between the three-quark and the five-quark states. Our lattice QCD analysis suggests that the flavor-singlet three-quark state is so heavy that the $Λ$(1405) cannot be identified as the three-quark state, which supports the possibility of the molecular-state picture of the $Λ$(1405). Second, we study thermal properties of the scalar glueball in an anisotropic lattice QCD, and find about 300 MeV mass reduction near the QCD critical temperature from the pole-mass analysis. Finally, we study the three-quark potential, which is responsible to the baryon properties. The detailed lattice QCD analysis for the 3Q potential indicates the Y-type flux-tube formation linking the three quarks.

hep-ph↗

arXiv2003

Detailed Lattice-QCD Study for the Three-Quark Potential and Y-type Flux-Tube Formation

We study the ground-state three-quark (3Q) potential $V_{\rm 3Q}^{\rm g.s.}$ and the excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$ using SU(3) lattice Q CD. 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, i.e., Y-ansatz, within 1%-level deviation. With lattice QCD, we calculate also the excited-state potential in the 3Q system, and find the gluonic excitation energy, $V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}$, to be about 1 GeV. This large gluonic-excitation energy would play an essential role to the success of the quark model for the low-lying hadrons in terms of the absence of the gluonic mode.

hep-lat↗

arXiv2003

Static Three-Quark Potential in SU(3) Lattice QCD Monte-Carlo Simulation

The static three-quark(3Q) potential is investigated in the SU(3) lattice QCD at the quenched level, using the standard Wilson action with $β=5.7 (a\simeq 0.2{\rm fm})$ and $12^3\times 24$. With the 3Q Wilson loop, the ground-state 3Q potential $V_{\rm 3Q}$ is calculated for 16 patterns of the 3Q configuration, using the smearing technique, which enhances the ground-state overlap of the 3Q operator. With the accuracy better than a few %, the lattice QCD data for $V_{\rm 3Q}$ are well described by a sum of the Coulomb term, a constant and the linear term which is proportional to the minimal length $L_{\rm min}$ of the flux-tube linking the 3 quarks. Our results seem to support the Y-type flux picture rather than $Δ$-type one. From the comparison of $V_{\rm 3Q}$ with the ${\rm Q}$-${\rm \bar{Q}}$ potential, we find the universality of the string tension, $σ_{\rm 3Q}\simeq σ_{\rm Q\bar{Q}}$ as well as the OGE relation on the Coulomb coefficient, $A_{\rm 3Q}\simeq {1/2}A_{\rm Q\bar{Q}}$.

hep-lat↗

arXiv2003

Behind the success of the quark model

The ground-state three-quark (3Q) potential $V_{\rm 3Q}^{\rm g.s.}$ and the excited-state 3Q potential $V_{\rm 3Q}^{\rm e.s.}$ are studied using SU(3) lattice QCD at the quenched level. For more than 300 patterns of the 3Q systems, the ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ is investigated in detail in lattice QCD with $12^3\times 24$ at $β=5.7$ and with $16^3\times 32$ at $β=5.8, 6.0$. As a result, the ground-state potential $V_{\rm 3Q}^{\rm g.s.}$ is found to be well described with Y-ansatz within the 1%-level deviation. From the comparison with the Q-$\rm\bar Q$ potential, we find the universality of the string tension as $σ_{\rm 3Q}\simeqσ_{\rm Q\bar Q}$ and the one-gluon-exchange result as $A_{\rm 3Q}\simeq\frac12 A_{\rm Q\bar Q}$. The excited-state potential $V_{\rm 3Q}^{\rm e.s.}$ is also studied in lattice QCD with $16^3\times 32$ at $β=5.8$ for 24 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 1GeV in the typical hadronic scale, which is relatively large compared with the excitation energy of the quark origin. This large gluonic excitation energy justifies the great success of the simple quark model.

hep-lat↗

arXiv2002

Three-quark ground-state potential in the SU(3) lattice QCD

With the smearing technique, the three-quark (3Q) ground-state potential $V_{\rm 3Q}$ is numerically extracted in the SU(3)$_c$ lattice QCD Monte Carlo simulation with $12^3 \times 24$ and $β=5.7$ at the quenched level. With accuracy better than a few %, $V_{\rm 3Q}$ is well described by a sum of a constant $C_{\rm 3Q}$, the two-body Coulomb part $-A_{\rm 3Q}\sum_{i<j} \frac1{|{\bf r}_i-{\bf r}_j|}$ and the three-body linear confinement part $σ_{\rm 3Q} L_{\rm min}$, where $L_{\rm min}$ denotes the minimal length of the color flux tube linking the three quarks. By comparing with the Q-$\bar {\rm Q}$ potential, we find a universal feature of the string tension as $σ_{\rm 3Q} \simeq σ_{\rm Q \bar Q}$ and the one-gluon-exchange result for the Coulomb coefficient as $A_{\rm 3Q} \simeq \frac12 A_{\rm Q \bar Q}$. All our results including the constant term are consistent with the requirement on the diquark limit in the lattice regularization.

hep-lat↗

arXiv2002

Detailed Analysis of the Three Quark Potential in SU(3) Lattice QCD

The static three-quark (3Q) potential is studied in detail 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. For more than 300 different patterns of the 3Q systems, we perform the accurate measurement of the 3Q Wilson loop with the smearing method, which reduces excited-state contaminations, and present the lattice QCD data of the 3Q ground-state potential $V_{\rm 3Q}$. We perform the detailed fit analysis on $V_{\rm 3Q}$ in terms of the Y-ansatz both with the continuum Coulomb potential and with the lattice Coulomb potential, and find that the lattice QCD data of the 3Q potential $V_{\rm 3Q}$ are well reproduced within a few % deviation by the sum of a constant, the two-body Coulomb term and the three-body linear confinement term $σ_{\rm 3Q} L_{\rm min}$, with $L_{\rm min}$ the minimal value of the total length of color flux tubes linking the three quarks. From the comparison with the Q-$\bar {\rm Q}$ potential, we find a universality of the string tension as $σ_{\rm 3Q} \simeq σ_{\rm Q \bar Q}$ and the one-gluon-exchange result for the Coulomb coefficients as $A_{\rm 3Q} \simeq \frac12 A_{\rm Q \bar Q}$. We investigate also the several fit analyses with the various ansätze: the Y-ansatz with the Yukawa potential, the $Δ$-ansatz and a more general ansatz including the Y and the $Δ$ ansätze in some limits. All these fit analyses support the Y-ansatz on the confinement part in the 3Q potential $V_{\rm 3Q}$, although $V_{\rm 3Q}$ seems to be approximated by the $Δ$-ansatz with $σ_Δ\simeq 0.53 σ$.

hep-lat↗

arXiv2001

SU(3) Lattice QCD Study for Static Three-Quark Potential

We study the static three-quark (3Q) potential in detail 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. For more than 200 patterns of the 3Q systems, we numerically derive 3Q ground-state potential $V_{3Q}$ from the 3Q Wilson loop with the smearing technique, which reduces excited-state contaminations. The lattice QCD data of $V_{3Q}$ are well reproduced within a few % deviation by a sum of a constant, the two-body Coulomb term and the three-body linear confinement term $σ_{3Q} L_{min}$, with $L_{min}$ the minimal value of total length of color flux tubes linking the three quarks. From the comparison with the Q-$\bar {Q}$ potential, we find a universality of the string tension as $σ_{3Q} \simeq σ_{\rm Q \bar Q}$ and the one-gluon-exchange result for Coulomb coefficients, $A_{3Q} \simeq \frac12 A_{\rm Q \bar Q}$.

hep-lat↗

arXiv2001

Three-Quark Potential in SU(3) Lattice QCD

The static three-quark (3Q) potential is measured in the SU(3) lattice QCD with $12^3 \times 24$ and $β=5.7$ at the quenched level. From the 3Q Wilson loop, the 3Q ground-state potential $V_{\rm 3Q}$ is extracted using the smearing technique for the ground-state enhancement. With accuracy better than a few %, $V_{\rm 3Q}$ is well described by a sum of a constant, the two-body Coulomb term and the three-body linear confinement term $σ_{\rm 3Q} L_{\rm min}$, where $L_{\rm min}$ denotes the minimal length of the color flux tube linking the three quarks. By comparing with the Q-$\bar {\rm Q}$ potential, we find a universal feature of the string tension, $σ_{\rm 3Q} \simeq σ_{\rm Q \bar Q}$, as well as the one-gluon-exchange result for the Coulomb coefficient, $A_{\rm 3Q} \simeq \frac12 A_{\rm Q \bar Q}$.

hep-lat↗

arXiv2000

$σ$ Exchange in the NN Interaction within the Chiral Unitary Approach

We study the nucleon-nucleon interaction in the isoscalar-scalar channel using t he chiral unitary approach. The $t$-matrix of the pion-pion scattering in this c hannel is summed up to all orders using the B-S equation. We find that the calcu lated results at long distances are close to those of the $σ$-exchange inte raction. In addition, there appears a shorter range repulsion in this channel.

nucl-th↗

arXiv2000

Static three quark potential in the quenched lattice QCD

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.

hep-lat↗