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Roca, L., & Oset, E. (2021). Scalar resonances in the D+ -> K-K+K+ decay. Phys. Rev. D, 103(3), 034020–9pp.
Abstract: We study theoretically the resonant structure of the double Cabibbo suppressed D+ -> K-K+K+ decay. We start from an elementary production diagram, considered subleading in previous approaches, which cannot produce a final K-K+ pair at the tree level but which we show to be able to provide the strength of the decay through final meson-meson state interaction. The different meson-meson elementary productions are related through SU(3), and the final rescattering is implemented from a suitable implementation of unitary extensions of chiral perturbation theory, which generate dynamically the scalar resonances1 f(0)(980) and a(0)(980). We obtain a good agreement with recent experimental data from the LHCb Collaboration with a minimal freedom in the fit and show the dominance of the a(0)(980) contribution close to the threshold of the K-K+ spectrum.
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Martinez Torres, A., Khemchandani, K. P., Roca, L., & Oset, E. (2020). Few-body systems consisting of mesons. Few-Body Syst., 61(4), 35–16pp.
Abstract: We present a work which is meant to inspire the few-body practitioners to venture into the study of new, more exotic, systems and to hadron physicists, working mostly on two-body problems, to move in the direction of studying related few-body systems. For this purpose we devote the discussions in the introduction to show how the input two-body amplitudes can be easily obtained using techniques of the chiral unitary theory, or its extensions to the heavy quark sector. We then briefly explain how these amplitudes can be used to solve the Faddeev equations or a simpler version obtained by treating the three-body scattering as that of a particle on a fixed center. Further, we give some examples of the results obtained by studying systems involving mesons. We have also addressed the field of many meson systems, which is currently almost unexplored, but for which we envisage a bright future. Finally, we give a complete list of works dealing with unconventional few-body systems involving one or several mesons, summarizing in this way the findings on the topic, and providing a motivation for those willing to investigate such systems.
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Roca, L., & Oset, E. (2010). Description of the f(2)(1270), rho(3)(1690), f(4)(2050), rho(5)(2350), f(6)(2510) resonances as multi-rho(770) states. Phys. Rev. D, 82(5), 054013–11pp.
Abstract: In a previous work regarding the interaction of two rho(770) resonances, the f(2)(1270) (J(PC) = 2(++)) resonance was obtained dynamically as a two-rho molecule with a very strong binding energy, 135 MeV per rho particle. In the present work we use the rho rho interaction in spin 2 and isospin 0 channel to show that the resonances rho(3)(1690) (3(--)), f(4)(2050) (4(++)), rho(5)(2350) (5(--)), and f(6)(2510) (6(++)) are basically molecules of increasing number of rho(770) particles. We use the fixed center approximation of the Faddeev equations to write the multibody interaction in terms of the two-body scattering amplitudes. We find the masses of the states very close to the experimental values and we get an increasing value of the binding energy per rho as the number of rho mesons is increased.
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Roca, L., & Oset, E. (2012). Scattering of unstable particles in a finite volume: The case of pi rho scattering and the a(1)(1260) resonance. Phys. Rev. D, 85(5), 054507–13pp.
Abstract: We present a way to evaluate the scattering of unstable particles quantized in a finite volume with the aim of extracting physical observables for infinite volume from lattice data. We illustrate the method with the pi rho scattering which generates dynamically the axial-vector a(1)(1260) resonance. Energy levels in a finite box are evaluated both considering the rho as a stable and unstable resonance and we find significant differences between both cases. We discuss how to solve the problem to get the physical scattering amplitudes in the infinite volume, and hence phase shifts, from possible lattice results on energy levels quantized inside a finite box.
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Roca, L., & Oset, E. (2013). Lambda(1405) poles obtained from pi(0)Sigma(0) photoproduction data. Phys. Rev. C, 87(5), 055201–8pp.
Abstract: We present a strategy to extract the position of the two Lambda(1405) poles from experimental photoproduction data measured recently at different energies in the gamma p -> K+pi(0)Sigma(0) reaction at Jefferson Laboratory. By means of a chiral dynamics motivated potential with free parameters, we solve the Bethe-Salpeter equation in the coupled channels (K) over barN and pi Sigma in isospin I = 0 and parametrize the amplitude for the photonuclear reaction in terms of a linear combination of the pi Sigma -> pi Sigma and (K) over barN -> pi Sigma scattering amplitudes in I = 0, with a different linear combination for each energy. Good fits to the data are obtained with some sets of parameters, by means of which one can also predict the cross section for the K- p -> pi(0)Sigma(0) reaction. These later results help us decide among the possible solutions. The result is that the different solutions lead to two poles similar to those found in the chiral unitary approach. With the best result we find the two Lambda(1405) poles at 1385 – 68i MeV and 1419 – 22i MeV.
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