Final State Interactions in Hadronic D decays

We show that the large corrections due to final state interactions (FSI) in the D^+\to \pi^-\pi^+\pi^+, D^+_s\to \pi^-\pi^+\pi^+, and D^+\to K^-\pi^+\pi^+ decays can be accounted for by invoking scattering amplitudes in agreement with those derived from phase shifts studies. In this way, broad/overlapping resonances in S-waves are properly treated and the phase motions of the transition amplitudes are driven by the corresponding scattering matrix elements determined in many other experiments. This is an important step forward in resolving the puzzle of the FSI in these decays. We also discuss why the \sigma and \kappa resonances, hardly visible in scattering experiments, are much more prominent and clearly visible in these decays without destroying the agreement with the experimental \pi\pi and K\pi low energy S-wave phase shifts.Comment: 22 pages, 6 figures, 5 tables. Minor changes. We extend the discusion when quoting a reference and we include a new one. Some typos are fixe

Recent progress on the chiral unitary approach to meson meson and meson baryon interactions

We report on recent progress on the chiral unitary approach, analogous to the effective range expansion in Quantum Mechanics, which is shown to have a much larger convergence radius than ordinary chiral perturbation theory, allowing one to reproduce data for meson meson interaction up to 1.2 GeV. Applications to physical processes so far unsuited for a standard chiral perturbative approach are presented. Results for the extension of these ideas to the meson baryon sector are discussed, together with applications to kaons in a nuclear medium and $K^-$ atoms.Comment: Contribution to the KEK Tanashi Symposium on Physics of Hadrons and Nuclei, Tokyo, December 1998, 10 pages, 3 postscript figures. To be published as a special issue of Nuclear Physics

Clues for the existence of two K1(1270)K_1(1270) resonances

The axial vector meson $K_1(1270)$ was studied within the chiral unitary approach, where it was shown that it has a two-pole structure. We reanalyze the high-statistics WA3 experiment $K^- p\to K^-\pi^+\pi^- p$ at 63 GeV, which established the existence of both $K_1(1270)$ and $K_1(1400)$, and we show that it clearly favors our two-pole interpretation. We also reanalyze the traditional K-matrix interpretation of the WA3 data and find that the good fit of the data obtained there comes from large cancellations of terms of unclear physical interpretation.Comment: published version in PRD; typos corrected; title changed to "Clues for the existence of two $K_1(1270)$ resonances

Two-photon and one photon-one vector meson decay widths of the f0(1370)f_0(1370), f2(1270)f_2(1270), f0(1710)f_0(1710), f2′(1525)f'_2(1525), and K2∗(1430)K^*_2(1430)

We calculate the radiative decay widths, two-photon ($\gamma\gamma$) and one photon-one vector meson ($V\gamma$), of the dynamically generated resonances from vector meson-vector meson interaction in a unitary approach based on the hidden-gauge Lagrangians. In the present paper we consider the following dynamically generated resonances: $f_0(1370)$, $f_0(1710)$, $f_2(1270)$, $f_2'(1525)$, $K^*_2(1430)$, two strangeness=0 and isospin=1 states, and two strangeness=1 and isospin=1/2 states. For the $f_0(1370)$ and $f_2(1270)$ we reproduce the previous results for the two-photon decay widths and further calculate their one photon-one vector decay widths. For the $f_0(1710)$ and $f_2'(1525)$ the calculated two-photon decay widths are found to be consistent with data. The $\rho^0\gamma$, $\omega\gamma$ and $\phi\gamma$ decay widths of the $f_0(1370)$, $f_2(1270)$, $f_0(1710)$, $f'_2(1525)$ are compared with the results predicted by other approaches. The $K^{*+}\gamma$ and $K^{*0}\gamma$ decay rates of the $K^*_2(1430)$ are also calculated and compared with the results obtained in the framework of the covariant oscillator quark model. The results for the two states with strangeness=0, isospin=1 and two states with strangeness=1, isospin=1/2 are predictions that need to be tested by future experiments.Comment: More discussions about the relation between qqbar states and dynamically generated states; version published in PRD

Optimization method for the determination of material parameters in damaged composite structures

An optimization method to identify the material parameters of composite structures using an inverse method is proposed. This methodology compares experimental results with their numerical reproduction using the finite element method in order to obtain an estimation of the error between the results. This error estimation is then used by an evolutionary optimizer to determine, in an iterative process, the value of the material parameters which result in the best numerical fit. The novelty of the method is in the coupling between the simple genetic algorithm and the mixing theory used to numerically reproduce the composite behavior. The methodology proposed has been validated through a simple example which illustrates the exploitability of the method in relation to the modeling of damaged composite structures.Peer ReviewedPostprint (author’s final draft

Recent developments in chiral dynamics of hadrons and hadrons in a nuclear medium

In this talk I present recent developments in chiral dynamics of hadrons and hadrons in a medium addressing the following points: interaction of the octet of pseudoscalar mesons with the octet of baryons of the nucleon, showing recent experimental evidence on the existence of two $\Lambda(1405)$ states, the interaction of the octet of pseudoscalar mesons with the decuplet of baryons of the $\Delta$, with particular emphasis on the $\Lambda(1520)$ resonance, dynamically generated by this interaction. Then I review the interaction of kaons in a nuclear medium and briefly discuss the situation around the claims of deeply bound states in nuclei. The large renormalization of the $\Lambda(1520)$ in the nuclear medium is shown as another example of successful application of the chiral unitary techniques.Comment: Talk at the Fifth International Conference on Perspectives in Hadronic Physics: Particle-Nucleus and Nucleus-Nucleus Scattering at Relativistic Energies, Trieste, May 200

η→π0γγ\eta \to \pi^0 \gamma \gamma decay within unitarized chiral perturbation theory

We improve the calculations of the $\eta \to \pi^0 \gamma \gamma$ decay within the context of meson chiral lagrangians. We use a chiral unitary approach for the meson-meson interaction, thus generating the $a_0(980)$ resonance and fixing the longstanding sign ambiguity on its contribution. This also allows us to calculate the loops with one vector meson exchange, thus removing a former source of uncertainty. In addition we ensure the consistency of the approach with other processes. First, by using vector meson dominance couplings normalized to agree with radiative vector meson decays. And, second, by checking the consistency of the calculations with the related $\gamma \gamma \to \pi^0 \eta$ reaction. We find an $\eta \to \pi^0 \gamma \gamma$ decay width of $0.47\pm 0.10$ eV, in clear disagreement with published data but in remarkable agreement with the most recent measurement.Comment: 15 pages, 10 figures, published versio

Light scalars as tetraquarks or two-meson states from large Nc and unitarized Chiral Perturbation Theory

By means of unitarized Chiral Perturbation Theory it is possible to obtain a remarkable description of meson-meson scattering amplitudes up to 1.2 GeV, and generate poles associated to scalar and vector resonances. Since Chiral Perturbation Theory is the QCD low energy effective theory, it is possible then to study its large Nc limit where qqbar states are easily identified. The vectors thus generated follow closely a qqbar behavior, whereas the light scalar poles follow the large Nc behavior expected for a dominant tetraquark or two-meson structure.Comment: Invited Brief Report to appear in Modern Physcis Letters A. 15 page