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

The $\eta \to \pi^0 \gamma \gamma$ decay was investigated by the SND detector at VEPP-2M $e^+e^-$ collider in the reaction $e^+e^-\to\phi\to \eta\gamma$. Here we present the results and some details of this study. We report an upper limit (90% c.l.) $Br(\eta \to \pi^0 \gamma \gamma)<8.4\times 10^{-4}$ as our final result. Our upper limit does not contradict the earlier measurement by GAMS spectrometer. To facilitate future studies a rather detailed review of the problem is al...

In the experiment with the SND detector at the VEPP-2000 $e^+e^-$ collider the cross section for the process $e^+e^-\to\eta\pi^+\pi^-$ has been measured in the center-of-mass energy range from 1.22 to 2.00 GeV. Obtained results are in agreement with previous measurements and have better accuracy. The energy dependence of the $e^+e^-\to\eta\pi^+\pi^-$ cross section has been fitted with the vector-meson dominance model. From this fit the product of the branching fractions $B(\r...

A search for the exclusive radiative decays B->rho(770) gamma and B^0->omega(782) gamma is performed on a sample of 84 million BB-bar events collected by the BABAR detector at the PEP-II asymmetric e^+e^- collider. No significant signal is seen in any of the channels. We set preliminary upper limits of BR[B^0->rho^0 gamma]< 1.4 times 10^{-6}, BR[B^+ -> rho^+ gamma] < 2.3 times 10^{-6} and BR[B^0 -> omega gamma]< 1.2 times 10^{-6} at 90% Confidence Level. Combining these into ...

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.

The study of the pi^- p -> rho^0 n and pi^- p -> omega n amplitudes close and below the vector meson production threshold (1.2< sqrt(s) <1.8 GeV) reveals a rich dynamics arising from the presence of specific baryon resonances in this energy range. The interference pattern of the e^+e^- decays of the rho^0 and omega mesons produced in pi^- p reactions reflects directly this dynamics. We discuss this interference pattern in the pi^- p -> e^+e^- n reaction as function of the tot...

The $\rho^0-\omega$ interference has been studied in the dilepton invariant mass distribution spectra in the photonuclear reaction, but that is not done for the gamma-nucleon reaction. Recent past, the $e^+e^-$ invariant mass distribution spectrum in the $\gamma p$ reaction, i.e., $\gamma p \to pe^+e^-$ reaction, was measured at Jefferson Laboratory to look for the $\rho^0 -\omega$ interference in the multi-GeV region. To study the mechanism of this reaction, the differential...

Rare radiative decay $\phi\to\eta\pi^0\gamma$ was studied with SND detector at {VEPP-2M} electron-positron collider and its branching ratio was measured: $B(\phi\to\eta\pi^0\gamma)=(0.88\pm0.14\pm0.09)\cdot 10^{-4}$. Significant contribution of the $a_0(980)\gamma$ intermediate state was observed in the decay. The result is based on total integrated luminosity corresponding to $2\cdot10^7$ produced $\phi$ mesons.

The results of patial wave analysis of the omega pi- pi0 system, produced in the reaction pi- Be --> pi+ 2pi- 2pi0 Be at beam momentum of 37 GeV are presented. An indication of the resonant type structure with mass near 1.74 GeV and JpMetha=0-0+ in the omega rho- system was found. The decay branching ratio of a2(1320)- to omega pi- pi0 was measured. A wave with JpMetha=2+1+ shows a broad bump at M near 1.7 GeV. The decays pi2(1670)- --> omega rho- and a4(2040)- --> omega rho-...

In the SND experiment at VEPP-2M e^+e^- collider the phi(1020) ---> eta+gamma ---> 3pi^0+gamma decay was studied. The branching ratio B(phi--->eta+gamma) = (1.246 +- 0.025 +- 0.057)% was measured.

About 11 200 e^+e^- -> omega -> pi^+pi^-pi^0 events selected in the center of mass energy range from 760 to 810 MeV were used for the measurement of the \omega meson parameters. The following results have been obtained: sigma _{0}=(1457 \pm 23 \pm 19)nb, m_{\omega}=(782.71 \pm 0.07 \pm 0.04) MeV/c^{2}, \Gamma_{\omega}=(8.68 \pm 0.23 \pm 0.10) MeV, \Gamma_{e^+e^-}\cdot Br (\omega -> pi^+pi^-pi^0)= (0.528 \pm 0.012 \pm 0.007) \cdot 10^{-3} MeV.