Abstract: In this paper, we present a review of recent works on weak decay of heavy mesons and baryons with two mesons, or a meson and a baryon, interacting strongly in the final state. The aim is to learn about the interaction of hadrons and how some particular resonances are produced in the reactions. It is shown that these reactions have peculiar features and act as filters for some quantum numbers which allow to identify easily some resonances and learn about their nature. The combination of basic elements of the weak interaction with the framework of the chiral unitary approach allow for an interpretation of results of many reactions and add a novel information to different aspects of the hadron interaction and the properties of dynamically generated resonances.

Abstract: In this work we stu dy the rho B*(B) over bar* three-body system solving the Faddeev equations in the fixed center approximation. We assume the B*B* system forming a cluster, and in terms of the two-body rho B* unitarized scattering amplitudes in the local hidden gauge approach we find a new I(J(PC)) = 1(3(--)) state. The mass of the new state corresponds to a two-particle invariant mass of the rho B* system close to the resonant energy of the B-2(*) (5747), indicating that the role of this J = 2 resonance is important in the dynamical generation of the new state.

Abstract: We consider a recent T -matrix analysis by Albaladejo et al. (Phys Lett B 755: 337, 2016), which accounts for the J/psi pi and D*(D) over bar coupled-channels dynamics, and which successfully describes the experimental information concerning the recently discovered Z(c)(3900)(+/-). Within such scheme, the data can be similarly well described in two different scenarios, where Z(c)(3900) is either a resonance or a virtual state. To shed light into the nature of this state, we apply this formalism in a finite box with the aim of comparing with recent Lattice QCD (LQCD) simulations. We see that the energy levels obtained for both scenarios agree well with those obtained in the single-volume LQCD simulation reported in Prelovsek et al. (Phys Rev D 91: 014504, 2015), thus making it difficult to disentangle the two possibilities. We also study the volume dependence of the energy levels obtained with our formalism and suggest that LQCD simulations performed at several volumes could help in discerning the actual nature of the intriguing Z(c)(3900) state.

Abstract: The discovery of the D*(s0)(2317) and D-s1(2460) resonances in the charmed-strange meson spectra revealed that formerly successful constituent quark models lose predictability in the vicinity of two-meson thresholds. The emergence of non-negligible effects due to meson loops requires an explicit evaluation of the interplay between Q (q) over bar and (Q (q) over bar)(q (q) over bar) Fock components. In contrast to the c (s) over bar sector, there is no experimental evidence of J(P) = 0(+), 1(+) bottom-strange states yet. Motivated by recent lattice studies, in this work the heavy-quark partners of the D*(s0)(2317) and D-s1(2460) states are analyzed within a heavy meson chiral unitary scheme. As a novelty, the coupling between the constituent quark-model P-wave (B) over bar (s) scalar and axial mesons and the (B) over bar (()*()) K channels is incorporated employing an effective interaction, consistent with heavy-quark spin symmetry, constrained by the lattice energy levels.

Abstract: By solving the Muskhelishvili-Omnes integral equations, the scalar form factors of the semileptonic heavy meson decays D -> pi(l) over bar nu(l), D -> (K) over bar(l) over bar nu(l), (K) over bar -> pi(l) over bar nu(l) and (B) over bar (s) -> Kl (nu) over bar (l) are simultaneously studied. As input, we employ unitarized heavy meson-Goldstone boson chiral coupled-channel amplitudes for the energy regions not far from thresholds, while, at high energies, adequate asymptotic conditions are imposed. The scalar form factors are expressed in terms of Omn\`es matrices multiplied by vector polynomials, which contain some undetermined dispersive subtraction constants. We make use of heavy quark and chiral symmetries to constrain these constants, which are fitted to lattice QCD results both in the charm and the bottom sectors, and in this latter sector to the light-cone sum rule predictions close to q(2)=0 as well. We find a good simultaneous description of the scalar form factors for the four semileptonic decay reactions. From this combined fit, and taking advantage that scalar and vector form factors are equal at q(2)=0, we obtain |V-cd| = 0.244 +/- 0.022, |V-cs| = 0.945 +/- 0.041 and |V-ub| = (4.3 +/- 0.7)x10(-3) for the involved Cabibbo-Kobayashi-Maskawa (CKM) matrix elements. In addition, we predict the following vector form factors at q(2) = 0: |f(+)(D ->eta)(0)| = 0.01 +/- 0.05, |f(+)(Ds ->eta)(0)| = 0.50 +/- 0.08, |f(+)(Ds ->eta)(0)| = 0.73 +/- 0.03 and|f(+)((B) over bar ->eta)(0)| = 0.82 +/- 0.08, which might serve as alternatives to determine the CKM elements when experimental measurements of the corresponding differential decay rates become available. Finally, we predict the different form factors above the q(2)-regions accessible in the semileptonic decays, up to moderate energies amenable to be described using the unitarized coupled-channel chiral approach.