0000000000521868
AUTHOR
Alfredo Valcarce Mejía
A SU(4) circle times O(3) scheme for nonstrange baryons
4 pages, 3 tables.-- PACS nrs.: 12.39.Jh, 14.20.-c, 14.20.Gk.-- ISI Article Identifier: 000245667300027.-- ArXiv pre-print available at: http://arxiv.org/abs/hep-ph/0610257
Dynamical study of QQ-(u)over-bar (d)over-bar mesons
It has been recently conjectured by Selem and Wilczek [1] the existence of a ss-[ud] meson due to strong correlations between the two light antiquarks. We make a detailed study of this system within a dynamical quark model which has proven to be successful in reproducing the most important features of low-energy hadron phenomenology. Our results, obtained within a parameter-free calculation, show that the antidiquark component of the ssu d system indeed entails the stronger attraction, and drives its energy much lower than the N Xi threshold, but still above the (KK*-)-K-0 or (KK-)-K-*0 thresholds. We have also studied the ccu d and bbu d systems. Exotic mesons are only expected to exist in…
piB B-88 and sigmaB B-88 couplings from a chiral quark potential model
From an SU(2)⊗SU(2) chiral quark potential model incorporating spontaneous chiral symmetry breaking the asymptotic π and σ exchange pieces of the NN potential are generated. From them the πNN and σNN coupling constants can be extracted. The generalization to SU(3)⊗SU(3) allows for a determination of πB8B8 and σB8B8 coupling constants according to exact SU(3) hadron symmetry. The implementation of the values of the couplings at Q2=0 provided by QCD sum rules and/or phenomenology makes also feasible the extraction of the meson-baryon-baryon form factors. In this manner a quite complete knowledge of the couplings may be attained.
The rho-omega splitting in constituent quark models
PACS: 12.39.Jh; 14.40.-n.--ArXiv pre-print avaible at: http://arxiv.org/abs/0903.2949v1
Diquark-diquark correlations in the S-1(0)Lambda Lambda potential
We derive a ΛΛ potential from a chiral constituent quark model that has been successful in describing one, two and three nonstrange baryon systems. The resulting interaction at low energy is attractive at all distances due to the σ exchange term. The attraction allows for a slightly bound state just below the ΛΛ threshold. No short-range repulsive core is found. We extract the diquark-diquark contribution that turns out to be the most attractive and probable at small distances. At large distances the asymptotic behavior of the ΛΛ interaction provides a prediction for the σΛΛ coupling constant.
Microscopic NN-π NN*(1440) transition potential: determination of πNN*(1440) and πNN*(1440) coupling constants
A NN→NN∗(1440) transition potential, based on an effective quark-quark interaction and a constituent quark cluster model for baryons, is derived in the Born-Oppenheimer approach. The potential shows significant differences with respect to those obtained by a direct scaling of the nucleon-nucleon interaction. From its asymptotic behavior we extract the values of πNN∗(1440) and σNN∗(1440) coupling constants in a particular coupling scheme.
Describing non-QQ candidates
Despite the apparent simplicity of meson spectroscopy there are some states which cannot be accommodated in the usual q (q) over bar structure. Among them there are either exotic states as the X(1600) or the recently measured charm states D-sJ(*) and X(3872) and some of the light scalar mesons. In this work we present a possible description of these states in terms of tetraquarks.
Do c(c)over-barn(n)over-tilde bound states exist?
The four-quark system c (c) over barn (n) over tilde is studied in the framework of the constituent quark model. Using different types of quark-quark potentials, we solve the four-body Schrodinger equation by means of the hyperspherical harmonic formalism. Exploring the low laying J(PC) states for different isospin configurations no four-quark bound states have been found. Of particular interest is the possible four-quark structure of the X(3872). We rule out the possibility that this particle is a compact tetraquark system, unless additional correlations, either in the form of diquarks or at the level of the interacting potential, not considered in simple quark models do contribute.
Too many X's, Y's and Z's?
Heavy meson spectroscopy above open flavor thresholds has become a challenge both from the experimental and theoretical points of view. Experimentally, several signals have been interpreted as meson resonances with unusual properties; theoretically, such signals may be identified with meson-meson molecules or compact multiquark structures. We analyze the influence of thresholds on heavy meson spectroscopy comparing different flavor sectors and quantum numbers. The validity of a quark-model picture above open-flavor thresholds would severely restrict the number of channels that may lodge multiquark structures as meson-meson molecules.
b(b)over-bar description with a screened potential
Recent lattice QCD calculations suggest a rather abrupt transition in the confinig potential from a linear to a constant behavior. We analyze the effects of such a fast deconfinement in the simplest non-relativistic system, bottomonium.