New Data from SND Detector in Novosibirsk

The current status of experiments with SND detector at VEPP-2M e^+e^- collider in the energy range 2E_0=400-1400 MeV and recent results of data analysis for $\phi$, $\omega$ and $\rho$ decays and e^+e^- annihilation into hadrons are presented.Comment: 7 pages, 8 figures, Latex2e, uses espcrc1.sty. Talk given at 8th International Conference on Hadron Spectroscopy (HADRON 99), Beijing, China, 24-28 Aug 199

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

Experimental study of the e+e- -> pi0 gamma process in the energy region sqrt(s)=0.60-0.97 GeV

Results of the study of the e+e-->pi0 gamma process with SND detector at VEPP-2M collider in the c.m.s. energy range sqrt(s)=0.60-0.97 GeV are presented. Using 36513 selected events corresponding to a total integrated luminosity of 3.4 pb^-1 the e+e-->pi0 gamma cross section was measured. The energy dependence of the cross section was analyzed in the framework of the vector meson dominance model. The data are well described by a sum of phi,omega,rho0->pi0 gamma decay contributions with measured decay probabilities: Br(omega->pi0 gamma)=(9.34+-0.15+-0.31)% and Br(rho0->pi0 gamma)=(5.15+-1.16+-0.73)*10^-4 . The rho-omega relative interference phase is phi(rho,omega}=(-10.2+-6.5+-2.5) degree

Experimental Study of rho -> pi0 pi0 gamma and omega -> pi0 pi0 gamma Decays

The e+e- -> pi0 pi0 gamma process was studied in the SND experiment at VEPP-2M e+e- collider in the energy region 0.60-0.97 GeV. From the analysis of the energy dependence of measured cross section the branching ratios B(omega -> pi0 pi0 gamma)= (6.6 +1.4-0.8(stat) +-0.6(syst))x10^-5 and B(rho -> pi0 pi0 gamma)=(4.1 +1.0-0.9(stat) +-0.3(syst))x10^-5 were obtained.Comment: 16 pages, 7 figures, submitted to Phys. Lett.

Search for direct production of a2(1320) and f2(1270) mesons in e+e- annihilation

A search for direct production of C-even resonances a2(1320) and f2(1270) in e+e- annihilation was performed with SND detector at VEPP-2M e+e- collider. The upper limits of electronic widths of these mesons were obtained at 90% confidence level: Gamma(a2(1320) \to e+e-) < 0.56 eV, Gamma(f2(1270) \to e+e-) < 0.11 eV.Comment: 6 pages, 5 figures, 1 table. Submitted to Phys. Lett.

The process e+e−→π+π−π0e^+e^-\to\pi^+\pi^-\pi^0 in the energy range 2E_0=1.04 - 1.38 GeV

In the experiment with the SND detector at VEPP-2M e^+e^- collider the process $e^+e^-\to\pi^+\pi^-\pi^0$ was studied in the energy range 2E_0 from 1.04 to 1.38 GeV. A broad peak was observed with the visible mass $M_{vis}=1220\pm 20$ MeV and cross section in the maximum $\sigma_0\simeq 4$ nb. The peak can be interpreted as a $\omega$-like resonance $\omega (1200)$.Comment: 10 pages LATEX and 5 figure

Pion Form Factor at SND (new edition)

The update of the e^+e^-\to\pi^+\pi^- process cross section, measured in the energy region \sqrt{s}<1 GeV with SND detector at VEPP-2M collider is presented.Comment: Talk given at Int. Workshop e+e- Collisions from phi to psi, February 27 - March 2, 200

First Observation of PHI(1020)--->PI0+PI0+GAMMA Decay

In the SND experiment at the VEPP-2M electron-positron collider the PHI(1020)--->PI0+PI0+GAMMA decay was studied. The branching ratio B(PHI--->PI0+PI0+GAMMA)=(1.14+-0.10+-0.12)x10^{-4} was measured. It was shown, that the F0(980)GAMMA mechanism dominates in this decay and the 4-quark model of F0(980) describes our data most consistently.Comment: 6 pages, 6 figures, 1 table, Will be published in Phys.Lett.

Study of the ϕ\phi decays into π0π0γ\pi^0\pi^0\gamma and ηπ0γ\eta\pi^0\gamma final states

Radiative decays of the $\phi$ meson have been studied using a data sample of about 19 million $\phi$ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From selected $e^+e^-\to\pi^{0}\pi^{0}\gamma$ and $e^+e^-\to\eta\pi^{0}\gamma$ events the following model independent results have been obtained: \par $Br(\phi\to\pi^{0}\pi^{0}\gamma) = (0.92\pm 0.08\pm0.06)\times10^{-4}$ for $M_{\pi^{0}\pi^{0}}>700$ MeV, \par $Br(\phi\to\eta\pi^{0}\gamma) = (0.90\pm 0.24\pm 0.10)\times10^{-4}$. It is shown that the intermediate mechanism $f_{0}(980)\gamma$ dominates in the $\phi\to\pi^{0}\pi^{0}\gamma$ decay and the corresponding branching ratio is \par $Br(\phi\to f_{0}(980)\gamma)=(2.90\pm 0.21\pm1.54)\times10^{-4}$. The systematic error is dominated by the possible model uncertainty. \par Using the same data sample the upper limit has been obtained for the P- and CP-violating decay of $\eta$ at 90% CL: \par $Br(\eta\to\pi^{0}\pi^{0}) < 4.3\times10^{-4}$ >.Comment: 13 pages, 6 figures, Submitted to Phys. Lett.

π+\pi^+ and π0\pi^0 Polarizabilities from {γγ→ππ\gamma\gamma\rightarrow\pi\pi} Data on the Base of S-Matrix Approach

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 about $\pi \pi$ interaction. Application of these formulae for description of MARK-II \cite{M2} and Crystal Ball \cite{CB} data gives: $(\alpha-\beta)^{C}=(6.0\pm 1.2)\cdot 10^{-42} {\rm cm}^{3}$, $(\alpha-\beta)^{N}=(-1.4\pm 2.1)\cdot 10^{-42} cm^3$ (in units system $e^2 = 4 \pi \alpha$) at the experimental values of $\pi \pi$ scattering lengths. Both values are compartible with current algebra predictions.Comment: LaTeX, 14 pages plus 6 figures (not included, available upon request) , ISU-IAP.Th93-03, Irkuts