Abstract: We have studied the contribution of the state X(3930), coming from the interaction of the D ($) over bar and D-s(+) D ($) over bar (s) channels, to the B- -> K- J/psi omega decay. The purpose of this work is to offer a complementary tool to see if the X(3930) state observed in the D+ D- channel is the same or not as the X(3960) resonance claimed by the LHCb Collaboration from a peak in the D-s(+) D s mass distribution around threshold. We present results for what we expect in the J/psi omega mass distribution in the B- -> K- J/psi omega decay and conclude that a clear signal should be seen around 3930 MeV. At the same time, finding no extra resonance signal at 3960 MeV would be a clear indication that there is not a new state at 3960 MeV, supporting the hypothesis that the near-threshold peaking structure peak in the D-s(+) D-s(-) mass distribution is only a manifestation of a resonance below threshold.

Abstract: We have studied the meson-baryon interaction in the neutral S = -2 sector using an extended Unitarized Chiral Perturbation Theory, which takes into account not only the leading Weinberg-Tomozawa term (as all the previous studies in S = -2 sector), but also the Born terms and next-to-leading order contribution. Based on the SU(3) symmetry of the chiral Lagrangian we took most of the model parameters from the BCN model [1], where these were fitted to a large amount of experimental data in the neutral S = -1 sector. We have shown that our approach is able to generate dynamically both Xi(1620) and Xi(1690) states in very reasonable agreement with the data, and can naturally explain the puzzle with the decay branching ratios of Xi(1690). Our results clearly illustrate the reliability of chiral models implementing unitarization in coupled channels and the importance of considering Born and NLO contributions for precise calculations.

Abstract: We perform a fit to the LHCb data on the T-cc(3875) state in order to determine its nature. We use a general framework that allows to have the (DD & lowast;+)-D-0, (D+D & lowast;0) components forming a molecular state, as well as a possible nonmolecular state or contributions from missing coupled channels. From the fits to the data we conclude that the state observed is clearly of molecular nature from the (DD & lowast;+)-D-0, (D+D & lowast;0) components and the possible contribution of a nonmolecular state or missing channels is smaller than 3%, compatible with zero. We also determine that the state has isospin I=0 with a minor isospin breaking from the different masses of the channels involved, and the probabilities of the (DD & lowast;+)-D-0, (D+D & lowast;0) channels are of the order of 69% and 29% with uncertainties of 1%. The differences between these probabilities should not be interpreted as a measure of the isospin violation. Due to the short range of the strong interaction where the isospin is manifested, the isospin nature is provided by the couplings of the state found to the (DD & lowast;+)-D-0, (D+D & lowast;0) components, and our results for these couplings indicate that we have an I=0 state with a very small isospin breaking. We also find that the potential obtained provides a repulsive interaction in I=1, preventing the formation of an I=1 state, in agreement with what is observed in the experiment.

Abstract: We present a detailed study of the lowest-lying 1/2(-) and 3/2(-) Lambda Q resonances both in the heavy 2 2 quark (bottom and charm) and the strange sectors. We have paid special attention to the interplay between the constituent quark-model and chiral baryon-meson degrees of freedom, which are coupled using a unitarized scheme consistent with leading-order heavy quark symmetries. We show that the Lambda(b)(5912) [J(P) = 1/2(-)], Lambda(b)(5920) [J(P) = 3/2(-)] and the Lambda(c)(2625) [J(P) = 3/2-], and the Lambda(1520) [J(P) = 3/2(-)] admitting larger breaking corrections, are heavyquark spin-flavor siblings. They can be seen as dressed quark-model states with Sigma Q(()*()) pi molecular components of the order of 30%. The J(P)=1(-) Lambda(2595) has, however, a higher molecular 2 probability of at least 50%, and even values greater than 70% can be easily accommodated. This is because it is located almost on top of the threshold of the Sigma(c)pi pair, which largely influences its properties. Although the light degrees of freedom in this resonance would be coupled to spin-parity 1(-) as in the Lambda(b)(5912), Lambda(b)(5920) and Lambda(c)(2625), the Lambda(c)(2595) should not be considered as a heavy-quark spin-flavor partner of the former ones. We also show that the Lambda(1405) chiral two-pole pattern does not have analogs in the 1 – charmed and bottomed sectors, because the 2 N D-(*()) and N (B) over bar (()*()) channels do not play for heavy quarks the decisive role that the N (K) over bar does in the strange sector, and the notable influence of the bare quark-model states for the charm and bottom resonances. Finally, we predict the existence of two Lambda(b)(6070) and two Lambda(c)(2765) heavy-quark spin and flavor sibling odd parity states.