LHCb pentaquarks in constituent quark models

The recently discovered $P_c(4380)^+$ and $P_c(4450)^+$ states at LHCb have masses close to the $\bar D\Sigma_c^*$ and $\bar D^*\Sigma_c$ thresholds, respectively, which suggest that they may have significant meson-baryon molecular components. We analyze these states in the framework of a constituent quark model which has been applied to a wide range of hadronic observables, being the model parameters, therefore, completely constrained. The $P_c(4380)^+$ and $P_c(4450)^+$ are studied as molecular states composed by charmed baryons and open charm mesons. Several bound states with the proper binding energy are found in the $\bar D\Sigma_c^*$ and $\bar D^*\Sigma_c$ channels. We discuss the possible assignments of these states from their decay widths. Moreover, two more states are predicted, associated with the $\bar D\Sigma_c$ and $\bar D^* \Sigma_c^*$ thresholds.Comment: 5 pages, 2 table

Heavy mesons in the Quark Model

Since the discovery of the $J/\psi$, the quark model was very successful in describing the spectrum and properties of heavy mesons including only $q\bar q$ components. However since 2003, with the discovery of the $X(3872)$, many states that can not be accommodated on the naive quark model have been discovered, and they made unavoidable to include higher Fock components on the heavy meson states. We will give an overview of the success of the quark model for heavy mesons and point some of the states that are likely to be more complicated structures such as meson-meson molecules.Comment: Contribution to the Proceedings of the 15th International Workshop on Meson Physics - MESON201

Puzzles in quarkonium hadronic transitions with two pion emission

The anomalously large rates of some hadronic transitions from quarkonium are studied using QCD multipole expansion (QCDME) in the framework of a constituent quark model which has been successful in describing hadronic phenomenology. The hybrid intermediate states needed in the QCDME method are calculated in a natural extension of our constituent quark model based on the Quark Confining String (QCS) scheme. Some of the anomalies are explained due to the presence of an hybrid state with a mass near the mass of the decaying resonance whereas other are justified by the presence of molecular components in the wave function. Some unexpected results are pointed out.Comment: Conference proceedings of the XI Quark Confinement and the Hadron Spectrum (CONFINEMENT XI). Saint Petersburg (Russia) from 8 to 12 September 201

The X(3872) and other possible XYZXYZ molecular states

We perform a coupled channel calculation of the $DD^*$ and $c\bar c$ sectors in the framework of a constituent quark model. The interaction for the $DD^*$ states is obtained using the Resonant Group Method (RGM) and the underlying quark interaction model. The coupling with the two quark system is performed using the $^3 P_0$ model. The X(3872) is found as a molecular state with a sizable $c\bar c$ component. A comparison with Belle and BaBar data has been done, finding a good agreement. Other possible molecular molecular states are discussed.Comment: 5 pages, 5 figures, Proceedings to the Hadron 2009 - XIII International Conference on Hadron Spectroscopy, Florida State University (USA