Observation of KS0K_S^0 semileptonic decays with CMD-2 detector

The decay $K_S^0 \to \pi e \nu$ has been observed by the CMD-2 detector at the e^+e^- collider VEPP-2M at Novosibirsk. Of 6 million produced $K_L^0K_S^0$ pairs, $75 \pm 13$ events of the $K_S^0 \to \pi e \nu$ decay were selected. The corresponding branching ratio is $B(K_S^0 \to \pi e \nu)=(7.2 \pm 1.4)\times10^{-4}$. This result is consistent with the evaluation of $B(K_S^0 \to \pi e \nu)$ from the $K_L^0$ semileptonic rate and $K_S^0$ lifetime assuming $\Delta S=\Delta Q$ .Comment: 7 pages, 6 figures, LaTex2e. Submitted to Phys.Lett.

First observation of the ϕ→π+π−γ\phi\to\pi^+\pi^-\gamma decay

Radiative decays of the $\phi$ meson have been studied using a data sample of about 20 million $\phi$ decays collected by the CMD-2 detector at VEPP-2M collider in Novosibirsk. From selected $e^+e^-\to\pi^{+}\pi^{-}\gamma$ events the $\phi\to\pi^{+}\pi^{-}\gamma$ decay has been observed for the first time. \par Under the assumption that the intermediate $f_{0}(980)\gamma$ state dominates in the $\phi \to \pi^+\pi^-\gamma$ decay, the corresponding branching ratio is $Br(\phi\to f_{0}(980)\gamma)=(1.93\pm 0.46\pm 0.50)\times10^{-4}$. \par Selected $e^+e^-\to\mu^+\mu^-\gamma$ events were used to obtain $Br(\phi\to\mu^+\mu^-\gamma) =(1.43\pm 0.45\pm 0.14)\times10^{-5}$ for $E_{\gamma}>20$ MeV. \par Using the same data sample, upper limits at 90% CL have been obtained for the C-violating decay of the $\phi$: $Br(\phi\to\rho\gamma) < 1.2\times10^{-5}$; and for the P- and CP-violating decay of the $\eta$: \par $Br(\eta\to\pi^+\pi^-) < 3.3\times10^{-4}$.Comment: 16 pages, 10 figures, Submitted to 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.

Measurement of the ϕ\phi meson parameters with CMD-2 detector at VEPP-2M Collider

About 300 000 $e^+e^-\to \phi\to K^0_L K^0_S$ events in the center of mass energy range from 984 to 1040 MeV were used for the measurement of the $\phi$ meson parameters. The following results have been obtained: $\sigma_0 = (1367 \pm 15 \pm 21) nb, m_{\phi}=(1019.504 \pm 0.011 \pm 0.033) MeV/c^2, \Gamma_\phi=(4.477 \pm 0.036 \pm 0.022) MeV, \Gamma_{e^+e^-}\cdot B(\phi\to K^0_L K^0_S) = (4.364 \pm 0.048 \pm 0.065)\cdot 10^{-4}$ MeV.Comment: 13 pages, 5 figures, 5 table