Abstract: Recent studies have shown that the well-established Lambda(c) (2595) resonance contains a large meson-baryon component, which can vary depending on the specific formalism. In this work, we examine such a picture by utilizing the compositeness condition and the large number of colors (N-c) expansion. We examine three different models fulfilling two body unitarily in coupled-channels, and adopting renormalization schemes where the mass of the Lambda(c)(2595) resonance is well described, but not necessarily its width, since we do not consider three body channels and work at the isospin symmetric limit. Both approximations might have an effect larger on the width than on the mass. In this context, our studies show that the compositeness of the Lambda(c)(2595) depends on the number of considered coupled channels, and on the particular regularization scheme adopted in the unitary approaches and, therefore, is model dependent. In addition, we perform an exploratory study of the Lambda(c)(2595) in the large N-c expansion, within a scheme involving only the pi Sigma(c) and K Xi(c)', channels, whose dynamics is mostly fixed by chiral symmetry. In this context and formulating the leading-order interaction as a function of N-c, we show that for moderate N-c > 3 values, the mass and width of the Lambda(c)(2595) deviate from those of a genuine qqq baryon, implying the relevance of meson-baryon components in its wave function. Furthermore, we study the properties of the Lambda(c)(2595), in the strict N-c -> infinity limit, using an extension of the chiral Weinberg-Tomozawa interaction to an arbitrary number of flavors and colors. This latter study hints at the possible existence of a (perhaps) subdominant qqq component in the Lambda(c)(2595) resonance wave function, which would become dominant when the number of colors gets sufficiently large.

Abstract: The aim of this paper is to investigate an efficient strategy that allows one to obtain pi pi phase shifts and rho meson properties from QCD lattice data with high precision. For this purpose we evaluate the levels of the pi pi system in the rho channel in finite volume using chiral unitary theory. We investigate the dependence on the pi mass and compare this with other approaches which use QCD lattice calculations and effective theories. We also illustrate the errors induced by using the conventional Luscher approach instead of a more accurate one that was recently developed that takes into account exactly the relativistic two-meson propagators. Finally, we make use of this latter approach to solve the inverse problem, getting pi pi phase shifts from “synthetic” lattice data, providing an optimal strategy and showing which accuracy is needed in these data to obtain the rho properties with a desired accuracy.

Abstract: Lattice QCD simulations provide a promising way to disentangle different interpretations of hadronic resonances, which might be of particular relevance to understand the nature of the so-called XYZ particles. Recent studies have shown that in addition to the well-established naive quark model picture, the axial-vector meson f(1)(1285) can also be understood as a dynamically generated state built upon the KK* interaction. In this work, we calculate the energy levels of the KK* system in the f(1)(1285) channel in finite volume using the chiral unitary approach. We propose to calculate the loop function in the dimensional regularization scheme, which is equivalent to the hybrid approach adopted in previous studies. We also study the inverse problem of extracting the bound state information from synthetic lattice QCD data and comment on the difference between our approach and the Luscher method.