We investigate the low-energy elasticDN interaction using a quark model that confines color and realizes dynamical chiral symmetry breaking. The model is defined by a microscopic Hamiltonian inspired in the QCD Hamiltonian in Coulomb gauge. Constituent quark masses are obtained by solving a gap equation, and baryon and meson bound-state wave functions are obtained using a variational method. We derive a low-energy meson-nucleon potential from a quark-interchange mechanism whose ingredients are the quark-quark and quarkantiquark interactions and baryon and meson wave functions, all derived from the same microscopic Hamiltonian.

Having in mind its future extension for theoretical investigations related to charmed nuclei, we develop a relativistic formalism for the nonmesonic weak decay of single-Λ hypernuclei in the framework of the independent-particle shell model and with the dynamics represented by the (π, K) one-meson-exchange model. Numerical results for the one-nucleon-induced transition rates of 12 Λ C are presented and compared with those obtained in the analogous nonrelativistic calculation. There is satisfactory agreement between the two approaches, and the most noteworthy difference is that the ratio Γn/Γp is appreciably higher and closer to the experimental value in the relativistic calculation. Large discrepancies between ours and previous relativistic calculations are found, for which we do not encounter any fully satisfactory explanation. The most recent experimental data is well reproduced by our results. In summary, we have achieved our purpose to develop a reliable model for the relativistic calculation of the nonmesonic weak decay of Λ-hypernuclei, which can now be extended to evaluate similar processes in charmed nuclei.

We investigate the production of exotic tetraquarks, QQqq ≡ T QQ (Q = c or b and q = u or d), in relativistic heavy-ion collisions using the quark coalescence model. The T QQ yield is given by the overlap of the density matrix of the constituents in the emission source with the Wigner function of the produced tetraquark. The tetraquark wave function is obtained from exact solutions of the four-body problem using realistic constituent models. The production yields are typically one order of magnitude smaller than previous estimations based on simplified wave functions for the tetraquarks. We also evaluate the consequences of the partial restoration of chiral symmetry at the hadronization temperature on the coalescence probability. Such effects, in addition to increasing the stability of the tetraquarks, lead to an enhancement of the production yields, pointing towards an excellent discovery potential in forthcoming experiments. We discuss further consequences of our findings for the search of exotic tetraquarks in central Pb+Pb collisions at the LHC.

We study the effect of a hot and dense medium on the binding energy of hadronic molecules with open-charm mesons. We focus on a recent chiral quark-model-based prediction of a molecular state in the ND system. We analyze how the two-body thresholds and the hadron-hadron interactions are modified when quark and meson masses and quark-meson couplings change in a function of the temperature and baryon density according to predictions of the Nambu-Jona-Lasinio model. We find that in some cases the molecular binding is enhanced in medium as compared to their free-space binding. We discuss the consequences of our findings for the search for exotic hadrons in high-energy heavy-ion collisions as well as in the forthcoming facilities FAIR or J-PARC. Recent developments in hadron physics have been motivated by the observation of exotic hadrons [1-4]. Most of them lie near open heavy-flavor thresholds implying that they may form the so-called hadronic molecules, that are colorless hadronic clusters loosely bound by a relatively weak residual interaction. This could be a possible situation of what is expected to occur, in general, for multiquark systems. In this respect, the recently discovered five-quark baryonic resonances by the LHCb Collaboration at the Large Hadron Collider (LHC) at CERN, P c (4380) + and P c (4450) + [5], have been interpreted as simple baryonmeson bound states. Also, some of the exotic mesonic states discovered in the hiddencharm and hidden-beauty sectors [6-9] might be well understood as meson-meson resonances. However, a comprehensive theoretical explanation of the nature of these exotic states is still missing [3, 10, 11]. The interest in structures containing hadrons with heavy flavors has also been recently reinvigorated by several studies about the existence of nuclear bound states with heavy mesons [12, 13] and baryons [14-17], the latter ones already predicted soon after the discovery of baryons possessing net charm [18-20]. In fact, there are theoretical estimations of the production cross sections as well as experimental requirements for producing charmed hypernuclei by means of charm exchange reactions on nuclei [21]. Last but not least, it is also worth mentioning the suggestion of possible bound states of charmonium in nuclei due to multiple gluon exchange [22, 23]. Such a possibility has been recently revisited by means of effective Lagrangians [24, 25] and effective Gaussian potentials [26, 27], stimulated by the lattice QCD suggestion of a weakly attractive interaction between charmonium and nucleons [28]. On the experimental side, there are exciting perspectives at extant and forthcoming facilities. At the LHC, all four collaborations, ALICE, ATLAS, CMS and LHCb, are engaged in searches for exotic hadrons. Particularly interesting is the possibility of the production of exotic hadrons in the hot and dense environment created in a high-energy heavy-ion collisions.In such an environment, heavy quarks are abundantly produced and they can pick up lightflavor quarks and antiquarks during t...

We study the temperature and baryon density dependence of the masses of the lightest charmed baryons Λ c , Σ c and Σ * c . We also look at the effects of the temperature and baryon density on the binding energies of the Λ c N and Λ c Λ c systems. Baryon masses and baryon-baryon interactions are evaluated within a chiral constituent quark model. Medium effects are incorporated in those parameters of the model related to the dynamical breaking of chiral symmetry, which are the masses of the constituent quarks, the σ and π meson masses, and quark-meson couplings. We find that while the in-medium Λ c mass decreases monotonically with temperature, those of Σ c and Σ * c have a nonmonotonic dependence. These features can be understood in terms of a simple group theory analysis regarding the one-gluon exchange interaction in those hadrons. The in-medium Λ c N and Λ c Λ c interactions are governed by a delicate balance involving a stronger attraction due to the decrease of the σ meson mass, suppression of coupled-channel effects and lower thresholds, leading to shallow bound states with binding energies of a few MeV. The Λ c baryon could possibly be bound to a large nucleus, in qualitative agreement with results based on relativistic mean field models or QCD sum rules. Ongoing experiments at RHIC or LHCb or the planned ones at FAIR and J-PARC may take advantage of the present results.