Related papers: Pion Scalar Form Factor and the Sigma Meson
We enforce chiral Ward identities on the vertices of the linear sigma model to take into account the width of the scalar sigma, considered as a true physical resonance. We consider pion scattering at very low energies and, from a fit to the…
We first review the recent accumulating evidences of the existence of a scalar-isoscalar meson with the mass 500 to 800 MeV which may be identified with the sigma meson as the quantum fluctuation of the amplitude of the chiral order…
We consider chiral perturbation theory with an explicit broad $\sigma$-meson and study its contribution to the scalar form factors of the pion and the nucleon. Our goal is to learn more about resonance saturation in the scalar sector.
The pion scalar form factor along with all existing S-wave iso-scalar $\pi\pi$-scattering phase shift data in the elastic region up to $1 {\rm GeV}^2$ are applied for a determination of the $f_0(500)$ and $f_0(980)$ meson parameters…
In this work the nature of the \sigma or f_0(600) resonance is discussed by evaluating its quadratic scalar radius, \la r^2\ra_s^\sigma. This allows one to have a quantitative estimate for the size of this resonance. We obtain that the…
Applying the effective amplitude, which is evidently consistent with general constraints from chiral symmetry, the pipi spectra in the relevant processes are analyzed, leading to a strong evidence for existence of the light sigma meson. It…
A variety of strong and electroweak interaction properties of the pion and the light scalar sigma meson are computed in a relativistic quark model. Under the assumption that the resulting coupling of these mesons to the constituent quarks…
An important role of the scalar isoscalar sigma-meson in the low-energy physics is discussed. The behavior of the sigma-meson in the hot and dense medium is studied. It is shown that in the vicinity of critical values of temperature(T) and…
We report on our recent progress in the generation of resonant behavior in unitarized meson-meson scattering amplitudes obtained from Chiral Perturbation Theory. These amplitudes provide simultaneously a remarkable description of the…
In this talk I summarize a recently proposed mechanism to understand pi pi scattering to 1 GeV. The model is motivated by the 1/Nc expansion to QCD, and includes a current algebra contact term and resonant pole exchanges. Chiral symmetry…
Model independent amplitude analyses of $\pi^- p_\uparrow \to \pi^- \pi^+ n$ on polarized target at 17.2 GeV/c reveal resonant structure of S-wave transversity amplitudes $|\bar S|^2\Sigma$ and $|S|^2\Sigma$ near 750 MeV. Simultaneous fit…
The analysis of the poles of the $\pi\pi$ scattering amplitude is shown to favour a dynamical origin of the sigma meson: it is created by a strongly attractive $\pi\pi$ interaction in the $J^{PC}=0^{++}I=0$ channel. In the limit…
The pi pi scattering is studied in two-flavor chiral models with a finite pion mass to investigate the nature of the sigma meson which is observed as the lowest scalar-isoscalar resonance. We compare several models with different origins of…
We study the structure of the sigma meson, the lowest-lying resonance of the pi pi scattering in the scalar-isoscalar channel, through the softening phenomena associated with the partial restoration of chiral symmetry. We build dynamical…
We present a determination of the pion-nucleon sigma-term based on a novel analysis of the $\pi N$ scattering amplitude in Lorentz covariant baryon chiral perturbation theory renormalized in the extended-on-mass-shell scheme. This…
We study the pion electromagnetic form factor in the modulus squared dispersion relation, and do the model independent extraction of the most important nonperturbative parameters in pion light-cone distribution amplitude. The motivation of…
In this talk I summarize recently proposed mechanisms to understand pi pi scattering to 1 GeV in an effective chiral Lagrangian. The Lagrangian includes higher resonances in addition to pions consistently with the chiral symmetry. Iso-spin…
Pion pion scattering is studied in a generalized linear sigma model which contains two scalar nonets (one of quark-antiquark type and the other of diquark-antidiquark type) and two corresponding pseudoscalar nonets. An interesting feature…
We derive a new parametrization for the scalar pion form factors that allows us to analyze data over a large energy range via the inclusion of resonances, and at the same time to ensure consistency with the high-accuracy dispersive…
A set of well known once subtracted dispersion relations with imposed crossing symmetry condition is used to modify unitary multichannel $S$ ($\pi\pi$, $K \bar K$, and $\eta\eta$) and $P$ ($\pi\pi$, $\rho 2\pi$, and $\rho\sigma$) wave…