The new analysis of the KLOE data on the phi->eta pi0 gamma decay

In this paper we present the fit to the recent high-statistical KLOE data on the phi -> eta pi^0 gamma decay. This decay mainly goes through the a_0 gamma intermediate state. The obtained results differ from those of the previous fits: data prefer a high a_0 mass and a considerably large a_0 coupling to the K\bar K}.Comment: 11 pages, 2 figure

ππ\pi\pi scattering S wave from the data on the reaction π−p→π0π0n\pi^-p\to\pi^0\pi^0n

The results of the recent experiments on the reaction $\pi^-p\to\pi^0\pi^0n$ performed at KEK, BNL, IHEP, and CERN are analyzed in detail. For the I=0 $\pi\pi$ S wave phase shift $\delta^0_0$ and inelasticity $\eta^0_0$ a new set of data is obtained. Difficulties emerging when using the physical solutions for the $\pi^0\pi^0$ S and D wave amplitudes extracted with the partial wave analyses are discussed. Attention is drawn to the fact that, for the $\pi^0\pi^0$ invariant mass, m, above 1 GeV, the other solutions, in principle, are found to be more preferred. For clarifying the situation and further studying the $f_0(980)$ resonance thorough experimental investigations of the reaction $\pi^-p\to\pi^0\pi^0n$ in the m region near the $K\bar K$ threshold are required.Comment: 17 pages, 5 figure

The decays omega(782), phi(1020) to 5 pi in the hidden local symmetry approach

The decays omega -> 2pi^+ 2pi^- pi^0 and omega -> pi^+ pi^- 3pi^0 are reconsidered in the hidden local symmetry approach (HLS) added with the anomalous terms. The decay amplitudes are analyzed in detail, paying the special attention to the Adler condition of vanishing the whole amplitude at vanishing momentum of any final pion. Combining the Okubo-Zweig-Iizuka (OZI) rule applied to the five pion final state, with the Adler condition, we calculate also the phi -> 2pi^+ 2pi^-pi^0 and phi -> pi^+ pi^- 3pi^0 decay amplitudes. The partial widths of the above decays are evaluated, and the excitation curves in e^+e^- annihilation are obtained, assuming reasonable particular relations among the parameters characterizing the anomalous terms of the HLS Lagrangian. The evaluated branching ratios B(phi -> pi^+ pi^- 3pi^0)~2x10^{-7} and B(phi -> 2pi^+ 2pi^- pi^0)~7x10^{-7} are such that with the luminosity L=500 pb^{-1} attained at DAFNE phi factory, one may already possess about 1685 events of the decays phi -> 5pi.Comment: 15 pages text, 12 pages of figures. Typos corrected, clarifying remarks added. Accepted for publication in Phys.Rev.

Study of the process e+e−→π+π−π0e^+e^- \to \pi^+\pi^-\pi^0 in the energy region s\sqrt[]{s} below 0.98 GeV

The cross section of the process $e^+e^-\to \pi^+\pi^-\pi^0$ was measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2M collider in the energy region $\sqrt[]{s}$ below 980 MeV. This measurement was based on about $1.2 \times 10^6$ selected events. The obtained cross section was analyzed together with the SND and DM2 data in the energy region $\sqrt[]{s}$ up to 2 GeV. The $\omega$-meson parameters: $m_\omega=782.79\pm 0.08\pm 0.09$ MeV, $\Gamma_\omega=8.68\pm 0.04\pm 0.15$ MeV and $\sigma(\omega\to 3\pi)=1615\pm 9\pm 57$ nb were obtained. It was found that the experimental data cannot be described by a sum of only $\omega$, $\phi$, $\omega^\prime$ and $\omega^{\prime\prime}$ resonances contributions. This can be interpreted as a manifestation of $\rho\to 3\pi$ decay, suppressed by $G$-parity, with relative probability $B(\rho\to 3\pi) = (1.01\pm^{0.54}_{0.36}\pm 0.034) \times 10^{-4}$.Comment: 41 pages REVTEX and 34 figure

Multipion decays of omega(782) and phi(1020)

Using the chiral model of pseudoscalar, vector, and axial vector mesons based on the hidden local symmetry added with the terms induced by the Wess-Zumino anomaly, the results of calculations of the branching fractions of the decays omega(782) and phi(1020) mesons to the 2pi+ 2pi- pi0, pi+ pi -3pi0 multipion states are presented.Comment: 4 pages. Talk presented by A.A. Kozhevnikov at the International Workshop "e+e- Collisions from Phi to Psi", February 27-March 2, 2006, BINP, Novosibirsk, Russian Federatio

Light Scalar Mesons from Phi to Psi

The following topics are considered. 1) Confinement, chiral dynamics, and light scalar mesons. 2) Chiral shielding of the $\sigma(600)$. 3) The $\phi$ meson radiative decays about nature of light scalar resonances. 4) The $J/\psi$ decays about nature of light scalar resonances. 5) The $a_0(980)\to\gamma\gamma$ and $f_0(980)\to\gamma\gamma$ decays about nature of light scalar resonances. 6) New round in $\gamma\gamma\to\pi^+\pi^-$, the Belle data. Arguments in favor of the four-quark model of the $a_0(980)$ and $f_0(980)$ mesons are given.Comment: 7 pages, 7 figures. Talk presented by N.N. Achasov at the International Workshop "e+e- Collisions from Phi to Psi", February 27--March 2, 2006, BINP, Novosibirsk, Russian Federatio

Study of the process e+e−→π+π−π0e^+e^- \to \pi^+\pi^-\pi^0 in the energy region s\sqrt[]{s} from 0.98 to 1.38 GeV.}

The cross section of the process $e^+e^-\to \pi^+\pi^-\pi^0$ was measured in the Spherical Neutral Detector experiment at the VEPP-2M collider in the energy region $\sqrt[]{s} = 980 \div 1380$ MeV. The measured cross section, together with the $e^+e^-\to \pi^+\pi^-\pi^0$ and $\omega\pi^+\pi^-$ cross sections obtained in other experiments, was analyzed in the framework of the generalized vector meson dominance model. It was found that the experimental data can be described by a sum of $\omega$, $\phi$ mesons and two $\omega^\prime$ and $\omega^{\prime\prime}$ resonances contributions, with masses $m_{\omega^\prime}\sim 1490$,$m_{\omega^{\prime\prime}}\sim 1790$ MeV and widths $\Gamma_{\omega^\prime}\sim 1210$, $\Gamma_{\omega^{\prime\prime}}\sim 560$ MeV. The analysis of the $\pi^+\pi^-$ invariant mass spectra in the energy region $\sqrt[]{s}$ from 1100 to 1380 MeV has shown that for their descriptionone should take into account the $e^+e^-\to\omega\pi^0\to\pi^+\pi^-\pi^0$ mechanism also. The phase between the amplitudes corresponding to the $e^+e^-\to\omega\pi$ and $e^+e^-\to\rho\pi$ intermediate states was measured for the first time. The value of the phase is close to zero and depends on energy.Comment: 29 pages REVTEX and 17 figures, accepted for publication in Physical Review