The quark model and b baryons

The recent observation at the Tevatron of (uub and ddb) baryons within 2 MeV of the predicted Σ_b-Λ_b splitting and of baryons at the Tevatron within a few mega electron volts (MeV) of predictions has provided strong confirmation for a theoretical approach based on modeling the color hyperfine interaction. The prediction of  = 5790-5800 MeV is reviewed and similar methods used to predict the masses of the excited states and . The main source of uncertainty is the method used to estimate the mass difference m_b-m_c from known hadrons. We verify that corrections due to the details of the interquark potential and to Ξ_b- mixing are small. For S-wave qqb states we predict , and . For states with one unit of orbital angular momentum between the b quark and the two light quarks we predict , and . Results are compared with those of other recent approaches.     

Excited heavy tetraquarks with hidden charm

The masses of the excited heavy tetraquarks with hidden charm are calculated within the relativistic diquark–antidiquark picture. The dynamics of the light quark in a heavy–light diquark is treated completely relativistically. The diquark structure is taken into account by calculating the diquark–gluon form factor. New experimental data on charmonium-like states above open charm threshold are discussed. The obtained results indicate that X(3872), Y(4260), Y(4360), Z(4248), Z(4433) and Y(4660) could be tetraquark states with hidden charm.     

Radial Excitations in the Global Colour Soliton Model

With the Munczek-Nemirovsky model of the effective gluon propagator in the global colour model, we study the radially excited solitons in which one quark is excited and the other two are at the ground state. The obtained masses of the two radial excitations are comparable with the experimental data.     

Doubly heavy-quark baryon spectroscopy and semileptonic decay

Working in the framework of a nonrelativistic quark model we evaluate the spectra and semileptonic decay widths for the ground state of doubly heavy Ξ and Ω baryons. We solve the three-body problem using a variational ansatz made possible by the constraints imposed by heavy-quark spin symmetry. In order to check the dependence of our results on the inter-quark interaction, we have used five different quark-quark potentials which include Coulomb and hyperfine terms coming from one-gluon exchange, plus a confining term. Our results for the spectra are in good agreement with a previous calculation done using a Faddeev approach. For the semileptonic decay our results for the total decay widths are in good agreement with the ones obtained within a relativistic quark model in the quark-diquark approximation.     

Correlators of hadron currents: The model and the ALEPH data on τ-decay

The model with the meson spectrum, consisting of zero-width equidistant resonances, is considered with connection to current correlators in coordinate space. The comparison of the explicit expressions for the correlators, obtained in this model, with the experimental data of ALEPH Collaboration on τ-decay is made and good agreement is found.     

Mesons in the Constituent Quark Model

The quark-antiquark （q^-q） spectrum is studied by solving the Schrōdinger equation in the framework of nonrelativistic constituent quark model. An overall good fit to the experimental data of meson is obtained. The interactions between quark and antiquark consist of quadratic colour confinement-exchange, one-gluon-exchange, and Goldstone-boson-exchange potentials.     

Radial excitations of heavy-light mesons

The recent discovery of D_s states suggests the existence of radial excitations. Our semirelativistic quark potential model succeeds in reproducing these states within one to two percent of accuracy compared with the experiments, D _s0(2860) and D _s ^*(2715), which are identified as 0⁺ and 1^- radial excitations (n = 2). We also present calculations of radial excitations for B/B _s heavy mesons. The relation between our formulation and the modified Goldberger-Treiman relation is also described.     

Chiral-invariant phase space model

The masses of the SU(3)×SU(6) hadrons are calculated in the chiral-invariant phase space (CHIPS) model as a sum of the mean energies of the quarks at a constant temperature T _c with the color-magnetic splitting and the color-electric shift. The masses of hadrons are parametrized by four constants: T _c, m_s, E _CE and A _CM. With the same number of parameters the CHIPS model fits the masses of hadrons better than the classic bag model. The small mass of the d-quark ( m _d = 2.7MeV) is used to prove that the isotopic shifts of hadrons can be explained by the mass difference between the d- and u-quarks. The dibaryon mass is estimated in CHIPS to be 200MeV higher than in the bag model. The prediction for the mass of the α^* cluster is about the same in both models. It is close to 4 ^. m _Δ. Received: 12 December 2001 / Accepted: 23 May 2002     

Gauge invariance in fractional field theories

The principle of local gauge invariance is applied to fractional wave equations and the interaction term is determined up to order in the coupling constant . Based on the Riemann-Liouville fractional derivative definition, the fractional Zeeman effect is used to reproduce the baryon spectrum accurately. The transformation properties of the non-relativistic fractional Schrödinger-equation under spatial rotations are investigated and an internal fractional spin is deduced.     

Vector and axial-vector mesons in Quasilocal Quark Models

We consider the SU(2) Quasilocal Quark Model of the NJL-type including vector and axial-vector four-fermion interaction vertices with derivatives. The mass spectrum and a set of model-independent relations for the ground and first-excited states are calculated. The chiral-symmetry restoration sum rules in these channels are imposed for matching to QCD at intermediate energies in order to get a number of constraints on parameters of the SU(2) QQM. Received: 15 January 2003 / Accepted: 10 February 2003 / Published online: 29 April 2003     

Kaonic Nuclear Cluster Kpp in Quark Delocalization Colour Screening Model

The quark-delocalization colour-screening model is employed to study the kaonic nuclear cluster K-pp system. The calculation shows that there is a strong effective attraction between kaon and protons. The bound state can be formed and the binding energy is estimated to be about 80 MeV, and the space configuration is a symmetrical linear triatomic molecule with radius 1.15 fm. The results also show that the quark delocalization is responsible for the strong attraction in the system and the colour screening adds a little attraction in this case.     

Static properties and semileptonic decays of doubly heavy baryons in a nonrelativistic quark model

We evaluate static properties and semileptonic decays for the ground state of doubly heavy Ξ, Ξ', Ξ ^* and Ω, Ω', Ω ^* baryons. Working in the framework of a nonrelativistic quark model, we solve the three-body problem by means of a variational ansatz made possible by heavy-quark spin symmetry constraints. To check the dependence of our results on the inter-quark interaction we use five different quark-quark potentials that include a confining term plus Coulomb and hyperfine terms coming from one-gluon exchange. Our results for static properties (masses, charge radii and magnetic moments) are, with a few exceptions for the magnetic moments, in good agreement with a previous Faddeev calculation. Our much simpler wave functions are used to evaluate semileptonic decays of doubly heavy Ξ, Ξ'(J = 1/2) and Ω, Ω'(J = 1/2) baryons. Our results for the decay widths are in good agreement with calculations done within a relativistic quark model in the quark-diquark approximation. An erratum to this article is available at .     

Theory of complete orthonormal sets of relativistic tensor wave functions and Slater tensor orbitals of particles with arbitrary spin in position, momentum and four-dimensional spaces

Using the complete orthonormal basis sets of nonrelativistic and quasirelativistic orbitals introduced by the author in previous papers for particles with arbitrary spin the new analytical relations for the 2(2s+1)-component relativistic tensor wave functions and Slater tensor orbitals in position, momentum and four-dimensional spaces are derived, where s=1/2,1,3/2,2,… . The relativistic tensor function sets are expressed through the corresponding nonrelativistic and quasirelativistic orbitals. The analytical formulas for overlap integrals over relativistic Slater tensor orbitals in position space are also derived.     

QCD Coulomb gauge approach to exotic hadrons

The Coulomb gauge Hamiltonian model is used to calculate masses for selected J^PC states consisting of exotic combinations of quarks and gluons: ggg glueballs (oddballs), qˉg hybrid mesons and qˉqˉ tetraquark systems. An odderon Regge trajectory is computed for the J^- glueballs with intercept much smaller than the pomeron, explaining its nonobservation. The lowest 1^-+ hybrid-meson mass is found to be just above 2.2GeV while the lightest tetraquark state mass with these exotic quantum numbers is predicted around 1.4GeV consistent with the observed π(1400).     

Ideal Mixing of Scalar Mesons and Hyperon-Nucleon Interaction

The mixing of scalar mesons is an open problem since their structure is unclear and controversial. By introducing the ideal mixing of scalar mesons, we dynamically investigate the hyperon-nucleon interaction in the chiral SU(3) quark model by solving the resonating group method (RGM) equation. The results show that when the ideal mixing of scalar mesons is considered and the mass of a κ meson is reduced to near 780 MeV, then the hyperon-nucleon scattering data can be reasonably described in the chiral SU(3) quark model. Hence we find that the experimental mass of the κ meson is around 780 MeV, and f₀(600) and f₀(980) mesons are the ideal mixing of scalar singlet and octet mesons.     

Diquark correlations in baryon spectroscopy and holographic QCD

We improve upon recent holographic predictions for the nucleon and delta resonance spectra and show how they emerge from a straightforward extension of the “metric soft wall” AdS/QCD dual. The resulting mass formula depends on a single adjustable parameter, characterizing confinement-induced IR deformations of the anti-de Sitter metric, and on the fraction of “good” (i.e. maximally attractive) diquarks in the baryon's quark model wave function. Despite their manifest simplicity, the predicted spectra describe the masses of all 48 observed light-quark baryon states and the underlying, linear trajectory structure with unprecedented accuracy.     

On the implicit integral character of Roothaan's expansion

The molecular generator coordinate Hartree-Fock method is reviewed. The connection between a quadrature solution of the generator coordinate Hartree-Fock equations and Roothaan's equations is stressed. The relation between linear expansion coefficients and generator coordinate weight functions is discussed and a numerical and analytical example is provided for the 1s orbital of the hydrogen atom represented as the integral transform of a Gaussian function. For the same example, the Gauss-Labatto quadrature is employed to emphasize the implicit integral character of Roothaan's equations. As a major conclusion, the interpretation that every LCAO calculation is actually performing integrations of the Griffin-Wheeler equations is advanced. Basis sets are therefore abscissas of the implicit quadrature used in the integration, whereas the linear coefficients automatically incorporate the corresponding weights. Subsequently, it is shown how to extract the generator coordinate weight function from the LCAO coefficients which has the advantage of being a characteristic of the physical system under study and not of the particular calculation being carried out. As such, basis set design becomes how to efficiently sample the weight function. Received: 13 June 1998 / Received in final form: 12 August 1998 / Accepted: 14 September 1998