Abstract: We study the weak decay of the Lambda(b) into J/psi K Xi. and J/psi eta Lambda states, and relate these processes to the Lambda(b) -> J/psi(K) over barN decay mode. The elementary weak transition at the quark level proceeds via the creation of a J/psi meson and an excited sud system with I = 0, which upon hadronization leads to (K) over barN or eta Lambda pairs. These states undergo final-state interaction in coupled channels and produce a final meson-baryon pair. The K. state only occurs via rescattering, hence making the Lambda(b) -> J/psi K Xi process very sensitive to the details of the meson-baryon interaction in strangeness S = -1 and isospin I = 0. We show that the corresponding invariant mass distribution is dominated by the next-to-leading-order terms of the chiral interaction. The I = 0 selectivity of this decay, and its large sensitivity to the higher-order terms, makes its measurement very useful and complementary to the K- p -> K Xi cross section data. The rates of the Lambda(b) -> J/psi K Xi and Lambda(b) -> J/psi eta Lambda invariant mass distributions are sizable compared to those of the Lambda(b) -> J/psi(K) over barN decay, which is measured experimentally, and thus, we provide arguments for an experimental determination of these decay modes that will help us understand better the chiral dynamics at higher energies.

Abstract: The hidden-charm pentaquark P-c(4450) observed recently by the LHCb collaboration may be of molecular nature, as advocated by some unitary approaches that also predict pentaquark partners in the strangeness S = -1 sector. In this work we argue that a hidden-charm strange pentaquark could be seen from the decay of the Lambda b, just as in the case of the non-strange P-c(4450), but looking into the J/psi eta Lambda decay mode and forming the invariant mass spectrum of J/psi Lambda pairs. In the model presented here, which assumes a standard weak decay topology and incorporates the hadronization process and final-state interaction effects, we find the J/psi eta Lambda final states to be populated with similar strength as the J/psi K- p states employed for the observation of the non-strange pentaquark. This makes the Lambda b -> J/psi eta Lambda decay to be an interesting process to observe a possible strange partner of the P-c(4450). We study the dependence of the J/psi Lambda mass spectra on various model ingredients and on the unknown properties of the strange pentaquark.

Abstract: We perform a unitary coupled channel study of the interaction of the D*D-+(0), D*D-0(+) channels and find a state barely bound, very close to isospin I = 0. We take the experimental mass as input and obtain the width of the state and the (DD0 pi-)-D-0+ mass distribution. When the mass of the T-cc state quoted in the experimental paper from raw data is used, the width obtained is of the order of the 80 keV, small compared to the value given in that work. Yet, when the mass obtained in an analysis of the data considering the experimental resolution is taken, the width obtained is about 43 keV and both the width and the (DD0 pi+)-D-0 mass distribution are in remarkable agreement with the results obtained in that latter analysis.

Abstract: We study for the first time the p Sigma(-) -> K- d and K- d -> p Sigma(-) reactions close to threshold and show that they are driven by a triangle mechanism, with the Lambda(1405), a proton and a neutron as intermediate states, which develops a triangle singularity close to the (K) over bard threshold. We find that a mechanism involving virtual pion exchange and the K- p -> pi(+)Sigma(-) amplitude dominates over another one involving kaon exchange and the K- p -> K- p amplitude. Moreover, of the two Lambda(1405) states, the one with higher mass around 1420 MeV, gives the largest contribution to the process. We show that the cross section, well within measurable range, is very sensitive to different models that, while reproducing (K) over barN observables above threshold, provide different extrapolations of the (K) over barN amplitudes below threshold. The observables of this reaction will provide new constraints on the theoretical models, leading to more reliable extrapolations of the (K) over barN amplitudes below threshold and to more accurate predictions of the Lambda(1405) state of lower mass.

Abstract: We perform a theoretical study of the D-s(+) ->pi(+)pi(+)pi(-)eta decay. We look first at the basic D-s(+) decay at the quark level from external and internal emission. Then we hadronize a pair or two pairs of q (q) over bar states to have mesons at the end. Posteriorly the pairs of mesons are allowed to undergo final state interaction, by means of which the a(0)(980), f(0)(980), a(1)(1260), and b(1)(1235) resonances are dynamically generated. The G parity is used as a filter of the possible channels, and from those with negative G parity only the ones that can lead to pi(+)pi(+)pi(-)eta at the final state are kept. Using transition amplitudes from the chiral unitary approach that generates these resonances and a few free parameters, we obtain a fair reproduction of the six mass distributions reported in the BESIII experiment.