Light- and strange-quark mass dependence of the ρ(770)\rho(770) meson revisited

Recent lattice data on $\pi\pi$-scattering phase shifts in the vector-isovector channel, pseudoscalar meson masses and decay constants for strange-quark masses smaller or equal to the physical value allow us to study the strangeness dependence of these observables for the first time. We perform a global analysis on two kind of lattice trajectories depending on whether the sum of quark masses or the strange-quark mass is kept fixed to the physical point. The quark mass dependence of these observables is extracted from unitarized coupled-channel one-loop Chiral Perturbation Theory. This analysis guides new predictions on the $\rho(770)$ meson properties over trajectories where the strange-quark mass is lighter than the physical mass, as well as on the SU(3) symmetric line. As a result, the light- and strange-quark mass dependence of the $\rho(770)$ meson parameters are discussed and precise values of the Low Energy Constants present in unitarized one-loop Chiral Perturbation Theory are given. Finally, the current discrepancy between two- and three-flavor lattice results for the $\rho(770)$ meson is studied.Comment: 44 pages, 41 figures, 11 table

Siria: El largo camino hacia la revolución

El invierno del año 2011 ha sido testigo del inicio de diversas revoluciones, revueltas y protestas de gran magnitud en numerosos países árabes. En este contexto de revuelta generalizada, Siria parecía emerger en un primer momento como la gran excepción regional. En efecto, a diferencia de lo acaecido en el resto de países árabes, hasta mediados del mes de Marzo los vientos de revuelta no soplarían con suficiente fuerza en este país. En este marco, el objetivo que motiva este breve artículo es el de entender por qué el pueblo sirio ha tardado casi tres meses en movilizarse contra su régimen y por qué, finalmente, se ha rebeladoThe winter of the year 2011 has witnessed the beginning of several revolutions, revolts and protests of great importance in many Arab countries. In this context of widespread revolt, Syria seemed to appear in the first moment as the main regional exception. Actually, in contrast with what was happening in the rest of the Arab countries, Syria wouldn’t be affected by the revolutionary winds until the middle of March. In this framework, the aim of this article is to understand why the Syrian people have taken almost three months to mobilize against the baathist regime and why they have finally revolte

Strange resonance poles from KπK\pi scattering below 1.8 GeV

In this work we present a determination of the mass, width and coupling of the resonances that appear in kaon-pion scattering below 1.8 GeV. These are: the much debated scalar $\kappa$-meson, nowdays known as $K_0^*(800)$, the scalar $K_0^*(1430)$, the $K^*(892)$ and $K_1^*(1410)$ vectors, the spin-two $K_2^*(1430)$ as well as the spin-three $K^*_3(1780)$. The parameters will be determined from the pole associated to each resonance by means of an analytic continuation of the $K\pi$ scattering amplitudes obtained in a recent and precise data analysis constrained with dispersion relations, which were not well satisfied in previous analyses. This analytic continuation will be performed by means of Pad\'e approximants, thus avoiding a particular model for the pole parameterization. We also pay particular attention to the evaluation of uncertainties.Comment: 13 pages, 12 figures. Accepted version to appear in Eur. Phys. J. C. Clarifications and references added, minor typos correcte