A. Valcarce

Constituent quark model study of the meson spectra

The spectrum is studied in a generalized constituent quark model constrained in the study of the NN phenomenology and the baryon spectrum. An overall good fit to the available experimental data is obtained. A detailed analysis of all sectors from the light-pseudoscalar and vector mesons to bottomonium is performed paying special attention to the existence and nature of some non well-established states. These results should serve as a complementary tool in distinguishing conventional quark model mesons from glueballs, hybrids or multiquark states.

Quark-model study of few-baryon systems

We review the application of non-relativistic constituent quark models to study one, two and three non-strange baryon systems. We present results for the baryon spectra, potentials and observables of the nucleon?nucleon (NN), N?, ?? and NN*(1440) systems, and binding energies of three non-strange baryon systems. We emphasize the observable effects related to quark antisymmetry and its interplay with quark dynamics.

The Nucleon-nucleon interaction in terms of quark degrees of freedom

A modified quark-quark interaction is applied to study the nucleon-nucleon interaction. The quark potential is suggested by instanton models and includes pion ( pi ) and sigma ( sigma ) exchanges as non-perturbative components and the one-gluon exchange as a perturbative one. The nucleon-nucleon potential derived from this model presents short-range repulsion and medium-range attraction besides the usual pion tail. Using this interaction the nucleon-nucleon phase shifts within the resonating group method have been calculated. They agree reasonably well with experimental values.

Towards an understanding of heavy baryon spectroscopy

The recent observation at CDF and D0 of Σb, Σb* and Ξb baryons opens the door to the advent of new states in the bottom baryon sector. The states measured provide sufficient constraints to fix the parameters of phenomenological models. One may therefore consistently predict the full bottom baryon spectra. For this purpose we have solved exactly the three-quark problem by means of the Faddeev method in momentum space. We consider our guidance may help experimentalists in the search for new bottom baryons and their findings will help in constraining further the phenomenological models. We identify particular states whose masses may allow to discriminate between the dynamics for the light quark pairs predicted by different phenomenological models. Within the same framework we also present results for charmed, doubly charmed, and doubly bottom baryons. Our results provide a restricted possible assignment of quantum numbers to recently reported charmed-baryon states. Some of them are perfectly described by D-wave excitations with JP = 5/2+, as the Λc(2880), Λc(3055), and Λc(3123).

Stability of multiquarks in a simple string model

A simple string model inspired by the strong-coupling regime of quantum chromodynamics is used as a potential for studying the spectrum of multiquark systems with two quarks and two antiquarks, with a careful treatment of the four-body problem. It is found that the ground state is stable, lying below the threshold for dissociation into two isolated mesons.

Faddeev study of heavy-baryon spectroscopy

We investigate the structure of heavy baryons containing a charm or a bottom quark. We employ a constituent quark model successful in the description of the baryon–baryon interaction which is consistent with the light-baryon spectra. We solve exactly the three-quark problem by means of the Faddeev method in momentum space. Heavy-baryon spectrum shows a manifest compromise between perturbative and nonperturbative contributions. The flavour dependence of the one-gluon exchange is analysed. We assign quantum numbers to some already observed resonances, and we predict the first radial and orbital excitations of all states with J = 1/2 or 3/2. We combine our results with heavy-quark symmetry and lowest order SU(3) symmetry breaking to predict the masses and quantum numbers of six still non-measured ground-state beauty baryons.

Spectroscopy of doubly charmed baryons

We study the mass spectrum of baryons with two and three charmed quarks. For double charm baryons the spin splitting is found to be smaller than standard quark-model potential predictions. This splitting is not influenced either by the particular form of the confining potential or by the regularization taken for the contact term of the spin-spin potential. We consistently predict the spectra for triply charmed baryons.

Charmonium spectroscopy above thresholds.

We present a systematic and self-consistent analysis of four-quark charmonium states and applied it to study compact four-quark systems and meson-meson molecules. Our results are robust and should serve to clarify the situation of charmonium spectroscopy above the threshold production of charmed mesons.

Four-quark spectroscopy within the hyperspherical formalism

We present a generalization of the hyperspherical harmonic formalism to study systems made of quarks and antiquarks of the same flavor. This generalization is based on the symmetrization of the

Exotic meson-meson molecules and compact four-quark states

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