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

Mechanisms of the f0(980)f_0(980) production in the reaction π−p→π0π0n\pi^-p\to\pi^0 \pi^0n

The model of the pure one-pion exchange mechanism, which gives a good description of the GAMS results on the alteration of the $S$-wave $\pi^0\pi^0$ mass spectrum in the $f_0(980)$ region in the reaction $\pi^-p\to\pi^0\pi^0n$ with increasing $-t$, is compared with the recent detailed data on the $m$ and $t$ distributions of the $\pi^-p\to\pi^0\pi^0n$ events obtained by the BNL-E852 Collaboration. It is shown that the predictions of this model are not confirmed by the BNL data. Therefore the observed phenomenon should be explained by the different exchange mechanism. It is most likely to be the $a_1$ exchange mechanism.Comment: 11 pages including 3 figure

New information on the strong isospin symmetry breaking in the reactions of the a00(980) and f0(980) resonance production

We discuss the isotopic symmetry breaking as a tool of studying the production mechanisms and nature of light scalar mesons. The anomalous isospin breaking effects can appear not only due to the a00(980)−f0(980)$a_0^0(980) - {f_0}(980)$ mixing, but also for any mechanism of the production of the KK¯$\bar{K}$ pairs with a definite isospin in the S wave

New information on the strong isospin symmetry breaking in the reactions of the

We discuss the isotopic symmetry breaking as a tool of studying the production mechanisms and nature of light scalar mesons. The anomalous isospin breaking effects can appear not only due to the $a_0^0(980) - {f_0}(980)$ mixing, but also for any mechanism of the production of the $\bar{K}$ pairs with a definite isospin in the S wave

Production of exotic resonance in ->rhorho

Translated from Russian. Published in Pis'ma Zh. Ehksp. Teor. Fiz. v. 40(8) p. 365-367SIGLEAvailable from Deutsches Elektronen-Synchrotron (DESY), Hamburg (DE) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman