Related papers: \sigma-Particle in Production Processes
The relation between scattering and production amplitudes are investigated, using a simple field theoretical model, from the general viewpoint of unitarity and the applicability of final state interaction(FSI-) theorem. The IA-method and…
We make a re-analysis of I=0 \pi\pi scattering phase shift \delta_0^0 through a new method of S-matrix parametrization (IA; interfering amplitude method), and show a result suggesting strongly for the existence of \sigma-particle --…
From a re-analysis of pi+ pi- -> pi+ pi- and pi+ pi- -> K K data, we found for pi-pi S-wave interaction below 2 GeV, sigma(400), f0(980), f0(1500) and f0(1780) clearly show up. f0(1370) can be included with a very small branching ratio to…
The theoretical analysis of the $\gamma\gamma \to \pi^0\eta$ process is presented within the energy range up to 1.4 GeV. The $S$-wave resonance $a_0(980)$ is described involving the coupled channel dispersive framework and the $D$-wave…
We present a phenomenological model for the $\gamma\gamma \to \pi^+\pi^-\pi^0$ reaction by including the production mechanism of the $a_2(1320)$ resonance, as well as the contributions from the $\sigma/f_0(500)\, \pi^0$ and $f_2(1270)\,…
We present a theoretical study of the $\gamma\gamma \to \pi\eta$ process from the threshold up to 1.4 GeV in the $\pi\eta$ invariant mass. For the s-wave $a_0(980)$ resonance state we adopt a dispersive formalism using a coupled-channel…
The light sigma-particle is, regardless of the strong criticism, reviving recently due to the works done from various sides. I review essential points of the controversies (especially related to our works) and of their answer:…
The COMPASS collaboration has collected the currently largest data set on diffractively produced $\pi^-\pi^-\pi^+$ final states using a negative pion beam of 190 GeV/c momentum impinging on a stationary proton target. This data set allows…
On the basis of a simultaneous description of the isoscalar s-wave channel of the $\pi\pi$ scattering (from the threshold up to 1.9 GeV) and of the $\pi\pi\to K\bar{K}$ process (from the threshold to $\sim$ 1.4 GeV) in the model-independent…
The production and properties of the resonances in the system of Pi+Pi- were studied in the reaction np --> npPi+Pi- at the momentum of incident neutrons Pn=(5.20 +/- 0.12)GeV/c. In this work in comparison with previous ones we made more…
Based on a sample of 7.8 million BESI $J/\psi$ events, the decay of $ J/\psi \to \omega \pi^+ \pi^-$ is studied. A low mass enhancement in the $\pi^+ \pi^-$ invariant mass spectrum recoiling against $\omega$ particle is clearly seen which…
We perform a theoretical study based on dispersion relations of the reaction \gamma\gamma\to \pi^0\pi^0 emphasizing the low energy region. We discuss how the f_0(980) signal emerges in \gamma\gamma\to \pi\pi within the dispersive approach…
The decay channel J/\psi->gamma omega omega, omega -> pi+ pi- pi0 is analyzed using a sample of 5.8x10^7 J/psi events collected with the BESII detector. The omega omega invariant mass distribution peaks at 1.76 GeV/c^2, just above the omega…
The Compton scattering on a charged pion and the process \gamma\gamma \to \pi^0\pi^0 are studied using the dispersion relations. Unknown parameters of the S-wave \pi\pi interaction, represented as a board Breit-Wignar resonance, and a sum…
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…
The evidences for sigma(600) and kappa(900) observed in our analyses on the pi pi and K pi scattering phase shift data are described, briefly. The analysis have been performed by the interfering amplitude method, which satisfies the…
We reanalyse the gamma-gamma scattering data and conclude that in the mass region below 1 GeV the cross section for gamma-gamma to pi^0-pi^0 can be largely explained by the one pion exchange process with pi-pi rescattering. The radiative…
The reaction gamma + p -> K+ + Sigma + pi was used to determine the invariant mass distributions or "line shapes" of the Sigma+ pi-, Sigma- pi+ and Sigma0 pi0 final states, from threshold at 1328 MeV/c^2 through the mass range of the…
We present a theoretical study of the $\gamma\gamma^{*} \to \pi^+\pi^-, \pi^0\pi^0$ processes from the threshold through the $f_2(1270)$ region in the $\pi\pi$ invariant mass. We adopt the Omn\`es representation in order to account for…
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…