Tau decays into two mesons: an overview

We review the state-of-the-art theoretical analyses of tau decays into a pair of mesons and a neutrino. The participant vector and scalar form factors, $f_{+}(s)$ and $f_{0}(s)$, are described in the frame of Chiral Perturbation Theory with resonances supplemented by dispersion relations, and the physical parameters of the intermediate resonances produced in the decay are extracted through the pole position of $f_{+,0}(s)$ in the complex plane. As a side result, we also determine the low-energy observables associated to the form factors. We hope our study to be of interest for present and future experimental analyses of these decays.Comment: 6 pages, 4 figures. Contribution to the Proceedings of the International Workshop "e+e- Collisions From Phi to Psi 2019", held in Novosibirsk, Russia, from February 25 to March 1, 2019. To be published in EPJ Web Of Conference

Combined analysis of the decays τ−→KSπ−ντ\tau^{-}\to K_{S}\pi^{-}\nu_{\tau} and τ−→K−ηντ\tau^{-}\to K^{-}\eta\nu_{\tau}

The potential of performing a combined analysis of the strangeness-changing decays $\tau^{-}\to K_{S}\pi^{-}\nu_{\tau}$ and $\tau^{-}\to K^{-}\eta\nu_{\tau}$ for unveiling the $K^{*}(1410)$ resonance pole parameters is illustrated. Our study is carried out within the framework of Chiral Perturbation Theory, including resonances as explicit degrees of freedom. Resummation of final state interactions are considered through a dispersive parameterization of the required form factors. A considerable improvement in the determination of the pole position with mass $M_{K^{*}(1410)}=1304\pm17$ MeV and width $\Gamma_{K^{*}(1410)}=171\pm62$ MeV is obtained.Comment: Talk given at XIth Quark Confinement and Hadron Spectrum, 8-12th September (2014), Saint Petersburg (Russia

La integración económica centroamericana: introducción al estudio de la unión aduanera y de las relaciones con la Unión Europea

Este documento de trabajo se centra en el estudio de las características y desafíos del proceso de integración centroamericana y analiza la situación y las alternativas de la unión aduanera existente en la región. También aborda las relaciones exteriores de Centro América, en particular con la Unión Europea (UE), los Estados Unidos (CAFTA) y México (Plan Puebla Panamá). Como ampliación del ámbito analítico tratado, las relaciones de Centro América con la UE se han contemplado desde el contexto general de las relaciones UE-América Latina (Diálogo del Grupo de Río). El documento enfatiza la importancia de reforzar la integración económica y mejorar las relaciones exteriores de las naciones centroamericanas. Por ello, se sugiere el establecimiento de un presupuesto común en la región, dotado de un sistema de ingresos basado en contribuciones nacionales y en los recursos procedentes de la unión aduanera, y provisto de un mecanismo de gasto capaz desarrollar proyectos estructurales comunes. Ese presupuesto común reforzaría el proceso de integración existente, mejoraría la inserción internacional de los países de Centro América e impulsaría el desarrollo económico y social en la región.Central American Economic Integration, Customs Union, European Union

A dispersive analysis of the pion vector form factor and τ−→K−KSντ\tau^{-}\to K^{-}K_{S}\nu_{\tau} decay

We explore the potential of a combined analysis of the decays $\tau^{-}\to\pi^{-}\pi^{0}\nu_{\tau}$ and $\tau^{-}\to K^{-}K_{S}\nu_{\tau}$ in the determination of the $\rho(1450)$ and $\rho(1700)$ resonance properties in the frame of resonance Chiral Theory supplemented by dispersion relations. On the one hand, we take advantage of the very precise data on the modulus squared of the pion vector form factor $|F_{V}^{\pi}|^{2}$ obtained by Belle to carry out a very dedicated analysis of the region where these resonances come up into play. Our study provides an improved treatment of the systematic theoretical errors and, as a most important result, we conclude that they dominate over the fit uncertainties in the determination of the $\rho(1450)$ and $\rho(1700)$ pole parameters and tend to be larger than in other determinations quoted in the literature where these errors were ignored or underestimated. The results of our analysis are summarized in numerical tables for the form factor modulus and phase, including both statistical and systematic errors, that can be found as ancillary material of this paper. As a byproduct, we also determine the low-energy observables of the pion vector form factor and the $\rho$-pole position. On the other hand, we benefit from the recent experimental data for the transition $\tau^{-}\to K^{-}K_{S}\nu_{\tau}$ released by BaBar to perform a first analysis of its decay spectrum and discuss the role of these resonances in this decay. We point out that higher-quality data on the $K^{-}K_{S}$ decay channel will allow compete with the $|F_{V}^{\pi}|^{2}$ ones and improve the determination of the $\rho(1450)$ and $\rho(1700)$ resonance parameters as a result of a combined analysis. We hope our study to be of interest for present and future experimental analysis of these decays.Comment: 35 pages, 8 figures, 2 ancillary file

Inferring phylogenetic networks with maximum pseudolikelihood under incomplete lineage sorting

Phylogenetic networks are necessary to represent the tree of life expanded by edges to represent events such as horizontal gene transfers, hybridizations or gene flow. Not all species follow the paradigm of vertical inheritance of their genetic material. While a great deal of research has flourished into the inference of phylogenetic trees, statistical methods to infer phylogenetic networks are still limited and under development. The main disadvantage of existing methods is a lack of scalability. Here, we present a statistical method to infer phylogenetic networks from multi-locus genetic data in a pseudolikelihood framework. Our model accounts for incomplete lineage sorting through the coalescent model, and for horizontal inheritance of genes through reticulation nodes in the network. Computation of the pseudolikelihood is fast and simple, and it avoids the burdensome calculation of the full likelihood which can be intractable with many species. Moreover, estimation at the quartet-level has the added computational benefit that it is easily parallelizable. Simulation studies comparing our method to a full likelihood approach show that our pseudolikelihood approach is much faster without compromising accuracy. We applied our method to reconstruct the evolutionary relationships among swordtails and platyfishes ($Xiphophorus$: Poeciliidae), which is characterized by widespread hybridizations

η′→ηππ\eta^{\prime}\to\eta\pi\pi decays in unitarized resonance chiral theory

We study the hadronic $\eta^{\prime}\to\eta\pi\pi$ decays within the framework of $U(3)_{L}\otimes U(3)_{R}$ Chiral Perturbation Theory including resonance states and the complete one-loop corrections. The amplitude is projected in partial waves and unitarized by means of the $N/D$ method resumming both the important $S$-and $D$-wave $\pi\pi$ and the subleading $S$-wave $\pi\eta$ final-state interactions. The participating scalar multiplet mass and coupling strengths are determined from fits to the Dalitz plot experimental data recently released by the A2 collaboration. As a byproduct of our analysis, the associated Dalitz-plot slope parameters are found to be $a=-0.072(7)_{\rm{stat}}(8)_{\rm{syst}}\,, b=-0.052(1)_{\rm{stat}}(2)_{\rm{syst}}\,, d=-0.051(8)_{\rm{stat}}(6)_{\rm{syst}}$, which lie in the ballpark of the current experimental and theoretical determinations.Comment: 45 pages, 12 figure