Garcia-Recio, C., Geng, L. S., Nieves, J., Salcedo, L. L., Wang, E., & Xie, J. J. (2013). Low-lying even parity meson resonances and spin-flavor symmetry revisited. Phys. Rev. D, 87(9), 096006–18pp.
Abstract: We review and extend the model derived in Garcia-Recio et al. [Phys. Rev. D 83, 016007 (2011)] to address the dynamics of the low-lying even-parity meson resonances. This model is based on a coupled-channels spin-flavor extension of the chiralWeinberg-Tomozawa Lagrangian. This interaction is then used to study the S-wave meson-meson scattering involving members not only of the pi octet, but also of the rho nonet. In this work, we study in detail the structure of the SU(6)-symmetry-breaking contact terms that respect (or softly break) chiral symmetry. We derive the most general local (without involving derivatives) terms consistent with the chiral-symmetry-breaking pattern of QCD. After introducing sensible simplifications to reduce the large number of possible operators, we carry out a phenomenological discussion of the effects of these terms. We show how the inclusion of these pieces leads to an improvement of the description of the J(P) = 2(+) sector, without spoiling the main features of the predictions obtained in the original model in the JP = 0(+) and J(P) = 1(+) sectors. In particular, we find a significantly better description of the I-G(J(PC)) =0(+)(2(++)), 1(-)(2(++)) and the I(JP)=1/2(2(+)) sectors, which correspond to the f(2)(1270), a(2)(1320), and K-2(*)(1430) quantum numbers, respectively.
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Garcia-Recio, C., Hidalgo-Duque, C., Nieves, J., Salcedo, L. L., & Tolos, L. (2015). Compositeness of the strange, charm, and beauty odd parity Lambda states. Phys. Rev. D, 92(3), 034011–14pp.
Abstract: We study the dependence on the quark mass of the compositeness of the lowest-lying odd parity hyperon states. Thus, we pay attention to Lambda-like states in the strange, charm, and beauty sectors which are dynamically generated using a unitarized meson-baryon model. In the strange sector we use a SU(6) extension of the Weinberg-Tomozawa meson-baryon interaction, and we further implement the heavy-quark spin symmetry to construct the meson-baryon interaction when charmed or beauty hadrons are involved. In the three examined flavor sectors, we obtain two J(P) = 1/2- and one J(P) = 3/2(-) Lambda states. We find that the. states which are bound states (the three Lambda(b)) or narrow resonances [one Lambda(1405) and one Lambda(c)(2595)] are well described as molecular states composed of s-wave meson-baryon pairs. The 1/2(-) wide Lambda(1405) and Lambda(c)(2595) as well as the 3/2(-) Lambda(1520) and Lambda(c)(2625) states display smaller compositeness so they would require new mechanisms, such as d-wave interactions.
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