Fumiko Okiharu - Academia.edu (original) (raw)

Papers by Fumiko Okiharu

AIP Conference Proceedings, 2006

We study multi-quark (3Q,4Q,5Q) systems in lattice QCD. We perform the detailed studies of multi-... more We study multi-quark (3Q,4Q,5Q) systems in lattice QCD. We perform the detailed studies of multi-quark potentials in lattice QCD to clarify the inter-quark interaction in multiquark systems. We find that all the multi-quark potentials are well described by the OGE Coulomb plus multi-Y-type linear potential, i.e., the multi-Y Ansatz. For multi-quark systems, we observe lattice QCD evidences of "flip-flop", i.e., flux-tube recombination. These lattice QCD studies give an important bridge between elementary particle physics and nuclear physics.

Journal of Physics: Conference Series, 2021

The LADYCATS (LADY Creators of Activities for Teaching Science) were founded in 2005 in cooperati... more The LADYCATS (LADY Creators of Activities for Teaching Science) were founded in 2005 in cooperation with Professor Hiroshi Kawakatsu (1945–2018) to encourage both female physics teachers and students who want to study physics more, and primary school teachers who feel unprepared to teach physics-based lessons. We have demonstrated ‘simple and beautiful experiments’ together for the past 14 years. Our concepts are as follows: the ‘simple’ experiments are easy to complete, while the ‘beautiful’ ones are interesting, and the ‘essential’ experiments demonstrate the principles of physics. We lost our leader, Professor Hiroshi Kawakatsu, in 2018. He always said, ‘Everyone has a right to learn’. We follow in Professor Kawakatsu’s footsteps and demonstrate several educational experiments that he liked and demonstrated.

Journal of Modern Physics, 2016

Motivated by the recent experimental discoveries of multi-quark candidates, e.g., the Θ + (1540),... more Motivated by the recent experimental discoveries of multi-quark candidates, e.g., the Θ + (1540), we study multi-quark systems in lattice QCD. First, we perform 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 2.24GeV after the chiral extrapolation. To single out the compact 5Q state from N K scattering states, we develop a new method with the hybrid-boundary condition (HBC), and find no evidence of the compact 5Q state below 1.75GeV in the negativeparity channel. Second, we perform the first study of the multi-quark potential in lattice QCD to clarify the inter-quark interaction in multi-quark systems. The 5Q potential V 5Q 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 V 4Q for the QQ-QQ system is also described by the OGE Coulomb plus multi-Y Ansatz, when QQ andQQ are well separated. The 4Q system is described as a "two-meson" state with disconnected flux tubes, when the nearest quark and antiquark pair is spatially close. We observe a lattice-QCD evidence for the "flip-flop", i.e., the flux-tube 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. * Talk presented by Fumiko Okiharu at "Quark Nuclear Physics 2005" (QNP05).

AIP Conference Proceedings, 2009

Nuclear Physics B - Proceedings Supplements, 2004

The distributions of chromo-electric and chromo-magnetic field associated with flux tubes in the ... more The distributions of chromo-electric and chromo-magnetic field associated with flux tubes in the baryon are studied in SU(3) lattice QCD. Maximal Abelian projection is used to reduce the statistical fluctuations. For a fixed source geometry, many different string configurations are possible. We investigated whether the string configuration, that is the choice of operator, biases the observed flux distribution.

Wewould like to introducehe history, aim, and our educational contents of LADY CATS (LADY Creator... more Wewould like to introducehe history, aim, and our educational contents of LADY CATS (LADY Creators of Activities for Teaching Science). We had demonstration "Simple and beautiful experiments" in ICPE2005, ICPE2006, ICPE2007, ASE2008. We will show and demonstrate some experimental tools. WHAT IS "LADY CATS"? LADY CATSis a science teachers' organization mainly consisting of women ranging from primary school teachers to university researchers. Our activities aim at encouraging students and teachers who are not interested in physics. Recently many primary teachers feel uncomfortable with science because they have studied only general science and they feel it is not enough to teach science, especially physics. There are many women teachers at primary schools. Moreover not many girls major physics, too. It causes there are fewer women physics teachers in higher education. We formed LADY CATS in 2005 to change these tendencies through our activities. We are dedicate...

In this workshop, we show the simple and beautiful experiments that attract students to physics. ... more In this workshop, we show the simple and beautiful experiments that attract students to physics. We prepare the materials and explain how to make the apparatus of the experiments, and you can make them with us together. Since the experiments we show are low cost and easily made of daily use, you can bring the experiments in your class soon. As an example, we show the experiments with which students can learn how we can detect radiation, how much are we exposed to the radiation from the natural environment and so on. Most of all, we hope students to have an attitude to make a decision on radiation in a levelheaded manner. This workshop is associated with the special session about Fukushima nuclear plant accident by H. Nitta, A. Kobayashi, and H. Kawakatsu.

Using SU(3) lattice QCD, we perform the detailed studies of the three-quark and the multi-quark p... more Using SU(3) lattice QCD, we perform the detailed studies of the three-quark and the multi-quark potentials. From the accurate calculation for more than 300 different patterns of 3Q systems, the static ground-state 3Q potential Vrm3Qrmg.s.V_{\rm 3Q}^{\rm g.s.}Vrm3Qrmg.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 Vrm3Qrme.s.V_{\rm 3Q}^{\rm e.s.}Vrm3Qrme.s. by diagonalizing the QCD Hamiltonian in the presence of three quarks, and find a large gluonic-excitation energy DeltaErm3QequivVrm3Qrme.s.−Vrm3Qrmg.s.\Delta E_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}DeltaErm3QequivVrm3Qrme.s.−Vrm3Qrmg.s. of about 1 GeV, which gives a physical reason of the success of the quark model. DeltaErm3Q\Delta E_{\rm 3Q}DeltaErm3Q is found to be reproduced by the ``inverse Mercedes Ansatz'', which ind...

Proceedings of the 12th Asia Pacific Physics Conference (APPC12), 2014

LADY CATS (LADY Creators of Activities for Teaching Science) is an organization of science teache... more LADY CATS (LADY Creators of Activities for Teaching Science) is an organization of science teachers. Our group includes a lot of female teachers. We have demonstrated "Simple and beautiful experiments" since ICPE 2005. We aim to encourage both students and teachers who are not interested in physics. Our concepts of experiments are as follows: the "simple" experiments which the teachers in the world can utilize in their classes easily, the "beautiful" experiments in which children get interested, and the "essential" experiments which can demonstrate the principles of physics. We demonstrate several educational experiments of our group.

Pentaquark 04 - Proceedings of the International Workshop, 2005

We perform the first study for the static penta-quark (5Q) potential in lattice QCD with β=6.0 an... more We perform the first study for the static penta-quark (5Q) potential in lattice QCD with β=6.0 and 16 3 × 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 QQ-QQ 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. * The lattice QCD simulation has been done on NEC-SX5 at Osaka University.

Pentaquark 04, 2005

Using the QCD string theory, we investigate the physical reason of the narrow width of penta-quar... more 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 gluonicexcitation 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.

Progress of Theoretical Physics Supplement, 2007

We study qqqq-type four-quark (4Q) systems in SU(3) c anisotropic quenched lattice QCD, using the... more We study qqqq-type four-quark (4Q) systems in SU(3) c anisotropic quenched lattice QCD, using the O(a)-improved Wilson (clover) fermion at β = 5.75 on 12 3 × 96 with renormalized anisotropy a s /a t = 4. For comparison, we first investigate the lowest qq scalar meson from the connected diagram and find its large mass of about 1.32 GeV after chiral extrapolation, and thus the lowest qq scalar meson corresponds to f 0 (1370). We investigate the lowest 4Q state in the spatially periodic boundary condition, and find that it is just a two-pion scattering state, as is expected. To examine spatially-localized 4Q resonances, we use the Hybrid Boundary Condition (HBC) method, where anti-periodic and periodic boundary conditions are imposed on quarks and antiquarks, respectively. By applying HBC on a finite-volume lattice, the threshold of the two-meson scattering state is raised up, while the mass of a compact 4Q resonance is almost unchanged. In HBC, the lowest 4Q state appears slightly below the two-meson threshold. To clarify the nature of the 4Q system, we apply the Maximum Entropy Method (MEM) for the 4Q correlator and obtain the spectral function of the 4Q system. From the combination analysis of MEM with HBC, we finally conclude that the 4Q system appears as a two-pion scattering state and there is no spatially-localized 4Q resonance in the quark-mass region of ms < m q < 2m s .

Physical Review Letters, 2005

The static penta-quark (5Q) potential V5Q is studied in SU(3) lattice QCD with 16 3 × 32 and β=6.... more The static penta-quark (5Q) potential V5Q is studied in SU(3) lattice QCD with 16 3 × 32 and β=6.0 at the quenched level. From the 5Q Wilson loop, V5Q is calculated in a gauge-invariant manner, with the smearing method to enhance the ground-state component. V5Q 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 QQ and 3Q potentials, we find a universality of the string tension, σ QQ ≃ σ3Q ≃ σ5Q, and the OGE result for Coulomb coefficients.

Physical Review D, 2005

The penta-quark(5Q) baryon is studied in anisotropic quenched lattice QCD with renormalized aniso... more The penta-quark(5Q) baryon is studied in anisotropic quenched lattice QCD with renormalized anisotropy as/at=4 for a high-precision mass measurement. The standard Wilson action at β = 5.75 and the O(a) improved Wilson quark action with κ=0.1210(0.0010)0.1240 are employed on a 12 3 ×96 lattice. Contribution of excited states is suppressed by using a smeared source. We investigate both the positive-and negative-parity 5Q baryons with I = 0 and spin J = 1/2 using a non-NK-type interpolating field. After chiral extrapolation, the lowest positive-parity state is found to have a mass, mΘ = 2.25 GeV, which is much heavier than the experimentally observed Θ + (1540). The lowest negative-parity 5Q appears at mΘ = 1.75 GeV, which is near the s-wave NK threshold. To distinguish spatially-localized 5Q resonances from NK scattering states, we propose a new general method imposing a "Hybrid Boundary Condition (HBC)", where the NK threshold is artificially raised without affecting compact five-quark states. The study using the HBC method shows that the negative-parity state observed on the lattice is not a compact 5Q but an s-wave NK-scattering state.

Physical Review D, 2005

We perform the detailed study of the tetraquark (4Q) potential V4Q for various QQ-QQ systems in S... more We perform the detailed study of the tetraquark (4Q) potential V4Q for various QQ-QQ systems in SU(3) lattice QCD with β = 6.0 and 16 3 × 32 at the quenched level. For about 200 different patterns of 4Q systems, V4Q is extracted from the 4Q Wilson loop in 300 gauge configurations, with the smearing method to enhance the ground-state component. We calculate V4Q for planar, twisted, asymmetric, and large-size 4Q configurations, respectively. Here, the calculation for large-size 4Q configurations is done by identifying 16 2 × 32 as the spatial size and 16 as the temporal one, and the long-distance confinement force is particularly analyzed in terms of the flux-tube picture. When QQ andQQ are well separated, V4Q is found to be expressed as the sum of the one-gluon-exchange Coulomb term and multi-Y type linear term based on the flux-tube picture. When the nearest quark and antiquark pair is spatially close, the system is described as a "two-meson" state. We observe a flux-tube recombination called as "flip-flop" between the connected 4Q state and the "two-meson" state around the level-crossing point. This leads to infrared screening of the long-range color forces between (anti)quarks belonging to different mesons, and results in the absence of the color van der Waals force between two mesons.

Nuclear Physics B - Proceedings Supplements, 2005

In SU(3) lattice QCD, we perform the detailed study for the ground-state three-quark (3Q) potenti... more In SU(3) lattice QCD, we perform the detailed study for the ground-state three-quark (3Q) potential V g.s. 3Q and the 1st excited-state 3Q potential V e.s. 3Q , 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 g.s. 3Q 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 fluxtube 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 e.s. 3Q , and find a large gluonic-excitation energy ∆E3Q ≡ V e.s. 3Q − V g.s. 3Q 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 V5Q in lattice QCD, and find that V5Q is well described by the sum of the OGE Coulomb plus multi-Y type linear potential.

Nuclear Physics A, 2005

Penta-quark (5Q) baryons are studied using anisotropic lattice QCD for high-precision measurement... more Penta-quark (5Q) baryons are studied using anisotropic lattice QCD for high-precision measurement of temporal correlators. A non-NK-type interpolating field is employed to study the 5Q states with J P = 1/2 ± and I = 0. In J P = 1/2 + channel, the lowest-lying state is found at m 5Q ≃ 2.25 GeV, which is too massive to be identified as the Θ + (1540). In J P = 1/2 − channel, the lowest-lying state is found at m 5Q ≃ 1.75 GeV. To distinguish a compact 5Q resonance state from an NK scattering state, a new method with "hybrid boundary condition (HBC)" is proposed. As a result of the HBC analysis, the observed state in the negative-parity channel turns out to be an NK scattering state.

The European Physical Journal C, 2004

AIP Conference Proceedings, 2005

We study the three-quark and multi-quark potentials in SU(3) lattice QCD. From the accurate calcu... more 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 g.s. 3Q 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 e.s. 3Q by diagonalizing the QCD Hamiltonian in the presence of three quarks, and find a large gluonic-excitation energy ∆E 3Q ≡ V e.s. 3Q − V g.s. 3Q of about 1 GeV, which gives a physical reason of the success of the quark model. ∆E 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.

AIP Conference Proceedings, 2006

We study multi-quark (3Q,4Q,5Q) systems in lattice QCD. We perform the detailed studies of multi-... more We study multi-quark (3Q,4Q,5Q) systems in lattice QCD. We perform the detailed studies of multi-quark potentials in lattice QCD to clarify the inter-quark interaction in multiquark systems. We find that all the multi-quark potentials are well described by the OGE Coulomb plus multi-Y-type linear potential, i.e., the multi-Y Ansatz. For multi-quark systems, we observe lattice QCD evidences of "flip-flop", i.e., flux-tube recombination. These lattice QCD studies give an important bridge between elementary particle physics and nuclear physics.

Journal of Physics: Conference Series, 2021

The LADYCATS (LADY Creators of Activities for Teaching Science) were founded in 2005 in cooperati... more The LADYCATS (LADY Creators of Activities for Teaching Science) were founded in 2005 in cooperation with Professor Hiroshi Kawakatsu (1945–2018) to encourage both female physics teachers and students who want to study physics more, and primary school teachers who feel unprepared to teach physics-based lessons. We have demonstrated ‘simple and beautiful experiments’ together for the past 14 years. Our concepts are as follows: the ‘simple’ experiments are easy to complete, while the ‘beautiful’ ones are interesting, and the ‘essential’ experiments demonstrate the principles of physics. We lost our leader, Professor Hiroshi Kawakatsu, in 2018. He always said, ‘Everyone has a right to learn’. We follow in Professor Kawakatsu’s footsteps and demonstrate several educational experiments that he liked and demonstrated.

Journal of Modern Physics, 2016

Motivated by the recent experimental discoveries of multi-quark candidates, e.g., the Θ + (1540),... more Motivated by the recent experimental discoveries of multi-quark candidates, e.g., the Θ + (1540), we study multi-quark systems in lattice QCD. First, we perform 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 2.24GeV after the chiral extrapolation. To single out the compact 5Q state from N K scattering states, we develop a new method with the hybrid-boundary condition (HBC), and find no evidence of the compact 5Q state below 1.75GeV in the negativeparity channel. Second, we perform the first study of the multi-quark potential in lattice QCD to clarify the inter-quark interaction in multi-quark systems. The 5Q potential V 5Q 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 V 4Q for the QQ-QQ system is also described by the OGE Coulomb plus multi-Y Ansatz, when QQ andQQ are well separated. The 4Q system is described as a "two-meson" state with disconnected flux tubes, when the nearest quark and antiquark pair is spatially close. We observe a lattice-QCD evidence for the "flip-flop", i.e., the flux-tube 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. * Talk presented by Fumiko Okiharu at "Quark Nuclear Physics 2005" (QNP05).

AIP Conference Proceedings, 2009

Nuclear Physics B - Proceedings Supplements, 2004

The distributions of chromo-electric and chromo-magnetic field associated with flux tubes in the ... more The distributions of chromo-electric and chromo-magnetic field associated with flux tubes in the baryon are studied in SU(3) lattice QCD. Maximal Abelian projection is used to reduce the statistical fluctuations. For a fixed source geometry, many different string configurations are possible. We investigated whether the string configuration, that is the choice of operator, biases the observed flux distribution.

Wewould like to introducehe history, aim, and our educational contents of LADY CATS (LADY Creator... more Wewould like to introducehe history, aim, and our educational contents of LADY CATS (LADY Creators of Activities for Teaching Science). We had demonstration "Simple and beautiful experiments" in ICPE2005, ICPE2006, ICPE2007, ASE2008. We will show and demonstrate some experimental tools. WHAT IS "LADY CATS"? LADY CATSis a science teachers' organization mainly consisting of women ranging from primary school teachers to university researchers. Our activities aim at encouraging students and teachers who are not interested in physics. Recently many primary teachers feel uncomfortable with science because they have studied only general science and they feel it is not enough to teach science, especially physics. There are many women teachers at primary schools. Moreover not many girls major physics, too. It causes there are fewer women physics teachers in higher education. We formed LADY CATS in 2005 to change these tendencies through our activities. We are dedicate...

In this workshop, we show the simple and beautiful experiments that attract students to physics. ... more In this workshop, we show the simple and beautiful experiments that attract students to physics. We prepare the materials and explain how to make the apparatus of the experiments, and you can make them with us together. Since the experiments we show are low cost and easily made of daily use, you can bring the experiments in your class soon. As an example, we show the experiments with which students can learn how we can detect radiation, how much are we exposed to the radiation from the natural environment and so on. Most of all, we hope students to have an attitude to make a decision on radiation in a levelheaded manner. This workshop is associated with the special session about Fukushima nuclear plant accident by H. Nitta, A. Kobayashi, and H. Kawakatsu.

Using SU(3) lattice QCD, we perform the detailed studies of the three-quark and the multi-quark p... more Using SU(3) lattice QCD, we perform the detailed studies of the three-quark and the multi-quark potentials. From the accurate calculation for more than 300 different patterns of 3Q systems, the static ground-state 3Q potential Vrm3Qrmg.s.V_{\rm 3Q}^{\rm g.s.}Vrm3Qrmg.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 Vrm3Qrme.s.V_{\rm 3Q}^{\rm e.s.}Vrm3Qrme.s. by diagonalizing the QCD Hamiltonian in the presence of three quarks, and find a large gluonic-excitation energy DeltaErm3QequivVrm3Qrme.s.−Vrm3Qrmg.s.\Delta E_{\rm 3Q} \equiv V_{\rm 3Q}^{\rm e.s.}-V_{\rm 3Q}^{\rm g.s.}DeltaErm3QequivVrm3Qrme.s.−Vrm3Qrmg.s. of about 1 GeV, which gives a physical reason of the success of the quark model. DeltaErm3Q\Delta E_{\rm 3Q}DeltaErm3Q is found to be reproduced by the ``inverse Mercedes Ansatz'', which ind...

Proceedings of the 12th Asia Pacific Physics Conference (APPC12), 2014

LADY CATS (LADY Creators of Activities for Teaching Science) is an organization of science teache... more LADY CATS (LADY Creators of Activities for Teaching Science) is an organization of science teachers. Our group includes a lot of female teachers. We have demonstrated "Simple and beautiful experiments" since ICPE 2005. We aim to encourage both students and teachers who are not interested in physics. Our concepts of experiments are as follows: the "simple" experiments which the teachers in the world can utilize in their classes easily, the "beautiful" experiments in which children get interested, and the "essential" experiments which can demonstrate the principles of physics. We demonstrate several educational experiments of our group.

Pentaquark 04 - Proceedings of the International Workshop, 2005

We perform the first study for the static penta-quark (5Q) potential in lattice QCD with β=6.0 an... more We perform the first study for the static penta-quark (5Q) potential in lattice QCD with β=6.0 and 16 3 × 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 QQ-QQ 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. * The lattice QCD simulation has been done on NEC-SX5 at Osaka University.

Pentaquark 04, 2005

Using the QCD string theory, we investigate the physical reason of the narrow width of penta-quar... more 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 gluonicexcitation 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.

Progress of Theoretical Physics Supplement, 2007

We study qqqq-type four-quark (4Q) systems in SU(3) c anisotropic quenched lattice QCD, using the... more We study qqqq-type four-quark (4Q) systems in SU(3) c anisotropic quenched lattice QCD, using the O(a)-improved Wilson (clover) fermion at β = 5.75 on 12 3 × 96 with renormalized anisotropy a s /a t = 4. For comparison, we first investigate the lowest qq scalar meson from the connected diagram and find its large mass of about 1.32 GeV after chiral extrapolation, and thus the lowest qq scalar meson corresponds to f 0 (1370). We investigate the lowest 4Q state in the spatially periodic boundary condition, and find that it is just a two-pion scattering state, as is expected. To examine spatially-localized 4Q resonances, we use the Hybrid Boundary Condition (HBC) method, where anti-periodic and periodic boundary conditions are imposed on quarks and antiquarks, respectively. By applying HBC on a finite-volume lattice, the threshold of the two-meson scattering state is raised up, while the mass of a compact 4Q resonance is almost unchanged. In HBC, the lowest 4Q state appears slightly below the two-meson threshold. To clarify the nature of the 4Q system, we apply the Maximum Entropy Method (MEM) for the 4Q correlator and obtain the spectral function of the 4Q system. From the combination analysis of MEM with HBC, we finally conclude that the 4Q system appears as a two-pion scattering state and there is no spatially-localized 4Q resonance in the quark-mass region of ms < m q < 2m s .

Physical Review Letters, 2005

The static penta-quark (5Q) potential V5Q is studied in SU(3) lattice QCD with 16 3 × 32 and β=6.... more The static penta-quark (5Q) potential V5Q is studied in SU(3) lattice QCD with 16 3 × 32 and β=6.0 at the quenched level. From the 5Q Wilson loop, V5Q is calculated in a gauge-invariant manner, with the smearing method to enhance the ground-state component. V5Q 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 QQ and 3Q potentials, we find a universality of the string tension, σ QQ ≃ σ3Q ≃ σ5Q, and the OGE result for Coulomb coefficients.

Physical Review D, 2005

The penta-quark(5Q) baryon is studied in anisotropic quenched lattice QCD with renormalized aniso... more The penta-quark(5Q) baryon is studied in anisotropic quenched lattice QCD with renormalized anisotropy as/at=4 for a high-precision mass measurement. The standard Wilson action at β = 5.75 and the O(a) improved Wilson quark action with κ=0.1210(0.0010)0.1240 are employed on a 12 3 ×96 lattice. Contribution of excited states is suppressed by using a smeared source. We investigate both the positive-and negative-parity 5Q baryons with I = 0 and spin J = 1/2 using a non-NK-type interpolating field. After chiral extrapolation, the lowest positive-parity state is found to have a mass, mΘ = 2.25 GeV, which is much heavier than the experimentally observed Θ + (1540). The lowest negative-parity 5Q appears at mΘ = 1.75 GeV, which is near the s-wave NK threshold. To distinguish spatially-localized 5Q resonances from NK scattering states, we propose a new general method imposing a "Hybrid Boundary Condition (HBC)", where the NK threshold is artificially raised without affecting compact five-quark states. The study using the HBC method shows that the negative-parity state observed on the lattice is not a compact 5Q but an s-wave NK-scattering state.

Physical Review D, 2005

We perform the detailed study of the tetraquark (4Q) potential V4Q for various QQ-QQ systems in S... more We perform the detailed study of the tetraquark (4Q) potential V4Q for various QQ-QQ systems in SU(3) lattice QCD with β = 6.0 and 16 3 × 32 at the quenched level. For about 200 different patterns of 4Q systems, V4Q is extracted from the 4Q Wilson loop in 300 gauge configurations, with the smearing method to enhance the ground-state component. We calculate V4Q for planar, twisted, asymmetric, and large-size 4Q configurations, respectively. Here, the calculation for large-size 4Q configurations is done by identifying 16 2 × 32 as the spatial size and 16 as the temporal one, and the long-distance confinement force is particularly analyzed in terms of the flux-tube picture. When QQ andQQ are well separated, V4Q is found to be expressed as the sum of the one-gluon-exchange Coulomb term and multi-Y type linear term based on the flux-tube picture. When the nearest quark and antiquark pair is spatially close, the system is described as a "two-meson" state. We observe a flux-tube recombination called as "flip-flop" between the connected 4Q state and the "two-meson" state around the level-crossing point. This leads to infrared screening of the long-range color forces between (anti)quarks belonging to different mesons, and results in the absence of the color van der Waals force between two mesons.

Nuclear Physics B - Proceedings Supplements, 2005

In SU(3) lattice QCD, we perform the detailed study for the ground-state three-quark (3Q) potenti... more In SU(3) lattice QCD, we perform the detailed study for the ground-state three-quark (3Q) potential V g.s. 3Q and the 1st excited-state 3Q potential V e.s. 3Q , 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 g.s. 3Q 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 fluxtube 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 e.s. 3Q , and find a large gluonic-excitation energy ∆E3Q ≡ V e.s. 3Q − V g.s. 3Q 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 V5Q in lattice QCD, and find that V5Q is well described by the sum of the OGE Coulomb plus multi-Y type linear potential.

Nuclear Physics A, 2005

Penta-quark (5Q) baryons are studied using anisotropic lattice QCD for high-precision measurement... more Penta-quark (5Q) baryons are studied using anisotropic lattice QCD for high-precision measurement of temporal correlators. A non-NK-type interpolating field is employed to study the 5Q states with J P = 1/2 ± and I = 0. In J P = 1/2 + channel, the lowest-lying state is found at m 5Q ≃ 2.25 GeV, which is too massive to be identified as the Θ + (1540). In J P = 1/2 − channel, the lowest-lying state is found at m 5Q ≃ 1.75 GeV. To distinguish a compact 5Q resonance state from an NK scattering state, a new method with "hybrid boundary condition (HBC)" is proposed. As a result of the HBC analysis, the observed state in the negative-parity channel turns out to be an NK scattering state.

The European Physical Journal C, 2004

AIP Conference Proceedings, 2005

We study the three-quark and multi-quark potentials in SU(3) lattice QCD. From the accurate calcu... more 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 g.s. 3Q 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 e.s. 3Q by diagonalizing the QCD Hamiltonian in the presence of three quarks, and find a large gluonic-excitation energy ∆E 3Q ≡ V e.s. 3Q − V g.s. 3Q of about 1 GeV, which gives a physical reason of the success of the quark model. ∆E 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.