Related papers: Resonance sum rules from large $N_C$ and partial w…
Using chiral low energy theorems and elastic unitarity assumption, the $\tau\to\pi K \nu $ decay is investigated. The vector and scalar $\pi K$ form factors are calculated. It is found that the $\pi K$ spectrum is dominated by the $K^*$…
We discuss $\pi\pi$ scattering in the framework of chiral perturbation theory. In particular, we recall the predictions made some time ago for the threshold parameters and for the phase shift difference $\delta_0^0-\delta_1^1$.
We match the $\pi\pi\to\pi\pi$ scattering amplitudes of Chiral Perturbation Theory with those from dispersion relations that respect analyticity and coupled channel unitarity, as well as accurately describing experiment. Their dependence on…
We present a determination of the mass, width and coupling of the strange resonances appearing in pion-kaon scattering below 1.8 GeV, namely the much debated $K^*_0(800)$ or $\kappa$, the scalar $K^*_0(1430)$, the $K^*(892)$ and $K^*(1410)$…
Corrections to $K\rightarrow\pi\pi\pi$ induced by vector and scalar meson exchange are investigated within chiral perturbation theory.
Nonrelativistic systems exhibiting collective magnetic behavior are analyzed in the framework of effective Lagrangians. The method, formulating the dynamics in terms of Goldstone bosons, allows to investigate the consequences of spontaneous…
With the aim of generating new constraints on the OZI suppressed couplings of chiral perturbation theory a set of six equations of the Roy and Steiner type for the $S$- and $P$-waves of the $\pi K$ scattering amplitudes is derived. The…
In the large $N_c$ approximation to $QCD$, the leading $\pp$ scattering amplitude is expressed as the sum of an infinite number of tree diagrams. We investigate the possibility that an adequate approximation at energies up to somewhat more…
We derive and analyse inequalities relating masses of the lightest pi-pi resonances (rho and sigma) to low energy couplings of the effective chiral Lagrangian in the limit of large number of colours.
The radiative decays of the phi meson are known to be a good source of information about the a0(980) and f0(980) scalar mesons. We discuss these decays starting from a non-linear model Lagrangian which maintains the (broken) chiral symmetry…
I discuss the recent attempts to build an effective chiral Lagrangian incorporating massive resonance states. A useful approximation scheme to organize the resonance Lagrangian is provided by the large-Nc limit of QCD. Integrating out the…
We review our studies on the rho and sigma resonances properties derived from the Inverse Amplitude Method. In particular, we study the leading $1/N_c$ behavior of the resonances masses and widths and their evolution with changing $m_\pi$.…
Chiral lagrangians provide a model independent description of the strongly interacting symmetry breaking sector. In this work it is first reviewed the LHC sensitivity to the chiral parameters (in the hardest case of non-resonant low-energy…
The experimental data on pi N scattering in the elastic energy region T_pi < 250 MeV are analyzed within the multichannel K-matrix approach with effective Lagrangians. Isospin invariance is not assumed in this analysis and the physical…
We calculate the combination $2a_0^{(0)}-5a_0^{(2)}$ (the Olsson sum rule) and the scattering lengths and effective ranges $a_1$, $a_2^{(I)}$ and $b_1$, $b_2^{(I)}$ dispersively (with the Froissart--Gribov representation) using, at low…
In this work we construct the $\pi\pi$ scattering amplitude $T^0_0$ with regular analytical properties in the $s$ complex plane, which describes simultaneously the data on the $\pi\pi$ scattering, $\phi\to\pi^0\pi^0\gamma$ decay, and…
A method is presented which makes considerably more transparent possible patterns behind low-energy scattering data. In particular, structures associated with resonances, such as locations, widths and heights, become visible with a naked…
We construct pi-pi amplitudes that fulfill exact elastic unitarity, account for one loop Chiral Perturbation Theory contributions and include all 1/Nc leading terms, with the only limitation of considering just the lowest-lying nonet of…
After a general introduction to the structure of effective field theories, the main ingredients of chiral perturbation theory are reviewed. Applications include the light quark mass ratios and pion-pion scattering to two-loop accuracy. In…
Using unitarity, analyticity and crossing symmetry, we derive universal sum rules for scattering amplitudes in theories invariant under an arbitrary symmetry group. The sum rules relate the coefficients of the energy expansion of the…