Related papers: On the determination of $\sigma$ from experimental…

Re-analyzing the old phase shift data of I=0, \pi\pi (I=1/2, K\pi) scattering, we show an evidence for existence of the \sigma-particle (\kappa-particle) with a comparatively light mass, which has been missing for a long time: In the…

We investigated the dependence of the $K^- d$ scattering length on models of $\bar{K}N$ interaction with one or two poles for $\Lambda(1405)$ resonance. The $\bar{K}NN - \pi \Sigma N$ system is described by coupled-channel Faddeev equations…

In the paper Phys. Rev. {\bf D83}, 054008 (2011) we constructed the $\pi\pi$ scattering amplitude $T^0_0$ with regular analytical properties in the $s$ complex plane, describing both experimental data and the results based on chiral…

The lightest QCD resonance, the sigma, has been recently fixed in the pi-pi scattering amplitude. The nature of this state remains nowadays one of the most intriguing and difficult issues in particle physics. Its coupling to photons is…

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…

Scalar mesons are a key expression of the infrared regime of QCD. The lightest of these is the $\sigma$. Now that its pole in the complex energy plane has been precisely located, we can ask whether this state is transiently ${\bar q}q$ or…

CERN measurements of pi(-)p->pi(-)pi(+)n on polarized target at 17.2 GeV/c enable experimental determination of partial wave production amplitudes below 1080 MeV. The measured S-wave transversity amplitudes provide evidence for a narrow…

We summarize the application of dispersion relations for the determination of low energy $\pi K$ interactions. In particular, we present our recent dispersive analyses for the complete study of both $\pi K\to \pi K$ and $\pi \pi \rightarrow…

We calculate the correlation functions for the $\bar K^0 p, \pi^+ \Sigma^0, \pi^0 \Sigma^+, \pi^+ \Lambda$, and $\eta \Sigma^+$ states, which in the chiral unitary approach predict an excited $\Sigma^*(1/2^-)$ state at the $\bar K N$…

Using lattice QCD we extract $\pi\pi$ scattering amplitudes with isospin--0,1,2 in low partial-waves at two values of the light quark mass corresponding to $m_\pi \sim 283$ and $330$ MeV. We confirm expectations of weak repulsion in…

We suggest the most model-independent and simple description of the $\gamma\gamma\rightarrow\pi\pi$ process near threshold in framework of S-matrix approach. The amplitudes contain the pion polarizabilities and rather restricted information…

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 use the Belle data on the $K^- p$ mass distribution of the $\Lambda_c^+ \to p K^- \pi^+$ reaction near the $\eta \Lambda$ threshold to determine the $\eta \Lambda $ scattering length and effective range. We show that from these data…

We measured a set of $\pi^\pm\Sigma^\mp$, $\pi^0\Sigma^0$, and $\pi^-\Sigma^0$ invariant mass spectra below and above the $\bar{K}N$ mass threshold in $K^-$-induced reactions on deuteron. We deduced the $S$-wave…

A pole in the D-pi S-wave analogous to the sigma and kappa is predicted at 2098 +- 40 - i(260 +- 40) MeV. The main objective of this paper is to provide formulae for fitting it to data.

A combined fit is made to E791 data on D->K-pi-pi, LASS data on K-pi elastic scattering, and BES II data on J/Psi->K*(890)-K-pi.In all cases, the K-pi S-wave is fitted well with a kappa resonance and Ko(1430); the kappa requires an…

Pion-kaon ($\pi K$) pairs occur frequently as final states in heavy-particle decays. A consistent treatment of $\pi K$ scattering and production amplitudes over a wide energy range is therefore mandatory for multiple applications: in…

When a resonance lies near the threshold of a heavier channel, an interesting feature can occur. The paradigmatic example employed here is the scalar isoscalar $f_0(980)$ resonance that couples to the lighter $\pi\pi$ and heavier $K\bar{K}$…

Recently BES at BEPC found evidence for the existence of the $\sigma$ meson in the process of $J/\Psi \to \sigma\omega \to\pi\pi\omega$. In this paper we firstly discuss the relevant coupling $g_{\sigma\pi\pi}$ and show that the linear…

Axiomatic principles such as analyticity, unitarity and crossing symmetry constrain the second derivative of the pi pi scattering amplitudes in some channels to be positive in a region of the Mandelstam plane. Since this region lies in the…