Narrow Width of Pentaquark Baryons in QCD String Theory (original) (raw)
Related papers
Role of Large Gluonic Excitation Energy for Narrow Width of Penta-Quark Baryons in QCD String Theory
Nuclear Physics A, 2005
We study the narrow decay width of low-lying penta-quark baryons in the QCD string theory in terms of gluonic excitations. 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. Since lattice QCD shows that the lowest gluonicexcitation energy takes a large value of about 1 GeV, 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) in the QCD string theory. This mechanism strongly suppresses the decay and leads to an extremely narrow decay width of the penta-quark system.
Lattice QCD Study for the Interquark Force in Three-Quark and Multi-Quark Systems
AIP Conference Proceedings, 2005
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.
Microscopic Study of the String Breaking in QCD
Ядерная физика, 2013
Theory of strong decays defines in addition to decay widths, also the channel coupling and the mass shifts of the levels above the decay thresholds. In the standard decay models of the 3 P 0 type the decay vertex is taken to be a phenomenological constant γ and such a choice leads to large mass shifts of all meson levels due to real and virtual decays, the latter giving a divergent contribution. Here we show that taking the microscopic details of decay vertex into account, one obtains new string width coefficient, which strongly suppresses virtual decay contribution. In addition for a realistic space structure of the decay vertex of highly excited states, the decay matrix elements appear to be strongly different from those, where the constant γ is used. From our analysis also follows that so-called flattening potential can imitate the effects of intermediate decay channels.
Study of quark confinement in baryons with lattice QCD
Nuclear Physics B - Proceedings Supplements, 2005
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.
Insights into the Quark–Gluon Vertex from Lattice QCD and Meson Spectroscopy
Few-Body Systems, 2015
By comparing successful quark-gluon vertex interaction models with the corresponding interaction extracted from lattice-QCD data on the quark's propagator, we identify common qualitative features which could be important to tune future interaction models beyond the rainbow ladder approximation. Clearly, a quantitative comparison is conceptually not simple, but qualitatively the results suggest that a realistic interaction should be relatively broad with a strong support at about 0.4 − 0.6 GeV and infrared-finite.
2007
We review the application of lattice QCD to the phenomenology of band c-quarks. After a short discussion of the lattice techniques used to evaluate hadronic matrix elements and the corresponding systematic uncertainties, we summarise results for leptonic decay constants, B-B mixing, semileptonic and rare radiative decays. A discussion of the determination of heavy quark effective theory parameters is followed by an explanation of the difficulty in applying lattice methods to exclusive nonleptonic decays.
Excited baryons in Large N QCD
Proceedings of International Workshop on Effective Field Theories: from the pion to the upsilon — PoS(EFT09), 2009
We discuss the strong decay widths and photoproduction helicity amplitudes of excited baryons in the context of the 1/N c expansion of QCD. The results show that in order to get a satisfactory description of the empirical data the sub-leading corrections in 1/N c are, in general, important. It is also found that, while one-body effective operators are dominant, there is some evidence for the need of two-body effects which, in general, are not included in quark model calculations.
Gluons, quarks, and the transition from nonperturbative to perturbative QCD
Proceedings of the …, 2001
Lattice-based investigations of two fundamental QCD quantities are described, namely the gluon and quark propagators in Landau gauge. We have studied the Landau gauge gluon propagator using a variety of lattices with spacings from a = 0.17 to 0.41 fm to explore finite volume and discretization effects. We also introduce the general method of "tree-level correction" to minimize the effect of lattice artefacts at large momenta. We demonstrate that it is possible to obtain scaling behavior over a very wide range of momenta and lattice spacings and to explore the infinite volume and continuum limits of the Landau-gauge gluon propagator. These results confirm the earlier conclusion that the Landau gauge gluon propagator is infrared finite. We study the Landau gauge quark propagator in quenched QCD using two forms of the O(a)-improved propagator with the Sheikholeslami-Wohlert quark action with the nonperturbative value for the clover coefficient csw and mean-field improvement coefficients in our improved quark propagators. We again implement an appropriate form of tree-level correction. We find good agreement between our improved quark propagators. The extracted value of infrared quark mass in the chiral limit is found to be 300 ± 30 MeV. We conclude that the momentum regime where the transition from nonperturbative to perturbative QCD occurs is Q 2 ≃ 4 GeV 2 .
Fine Structure of the QCD String Spectrum
Physical Review Letters, 2003
Using advanced lattice methods in Quantum Chromodynamics, three distinct scales are established in the excitation spectrum of the gluon field around a static quark-antiquark pair as the color source separation R is varied. On the shortest length scale, the excitations are consistent with states created by local gluon field operators arising from a multipole operator product expansion. An intermediate crossover region below 2 fm is identified with a dramatic rearrangement of the level orderings. On the largest length scale of 2-3 fm, the spectrum agrees with that expected for string-like excitations. The energies nearly reproduce asymptotic π/R string gaps, but exhibit a fine structure, providing important clues for developing an effective bosonic string description.
Observation of string breaking in QCD
Physical Review D, 2005
We numerically investigate the transition of the static quark-antiquark string into a static-light mesonantimeson system. Improving noise reduction techniques, we are able to resolve the signature of string breaking dynamics for n f 2 lattice QCD at zero temperature. This result can be related to properties of quarkonium systems. We also study short-distance interactions between two static-light mesons.