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.

Voronoi-Delaunay analysis of normal modes in a simple model glass

We combine a conventional harmonic analysis of vibrations in a one-atomic model glass of soft spheres with a Voronoi-Delaunay geometrical analysis of the structure. ``Structure potentials'' (tetragonality, sphericity or perfectness) are introduced to describe the shape of the local atomic configurations (Delaunay simplices) as function of the atomic coordinates. Apart from the highest and lowest frequencies the amplitude weighted ``structure potential'' varies only little with frequency. The movement of atoms in soft modes causes transitions between different ``perfect'' realizations of local structure. As for the potential energy a dynamic matrix can be defined for the ``structure potential''. Its expectation value with respect to the vibrational modes increases nearly linearly with frequency and shows a clear indication of the boson peak. The structure eigenvectors of this dynamical matrix are strongly correlated to the vibrational ones. Four subgroups of modes can be distinguished

Study of the process e+e- to pi+pi-pi+pi-pi0 with CMD-2 detector

The process e+e- to pi+ pi- pi+ pi- pi0 has been studied in the center of mass energy range 1280 -- 1380 MeV using 3.0 1/pb of data collected with the CMD-2 detector in Novosibirsk. Analysis shows that the cross section of the five pion production is dominated by the contributions of the eta pi+pi- and omega pi+pi- intermediate states.Comment: 8 pages, 3 figure. Submitted to Phys. Lett.

New precise determination of the \tau lepton mass at KEDR detector

The status of the experiment on the precise $\tau$ lepton mass measurement running at the VEPP-4M collider with the KEDR detector is reported. The mass value is evaluated from the $\tau^+\tau^-$ cross section behaviour around the production threshold. The preliminary result based on 6.7 pb$^{-1}$ of data is $m_{\tau}=1776.80^{+0.25}_{-0.23} \pm 0.15$ MeV. Using 0.8 pb$^{-1}$ of data collected at the $\psi'$ peak the preliminary result is also obtained: $\Gamma_{ee}B_{\tau\tau}(\psi') = 7.2 \pm 2.1$ eV.Comment: 6 pages, 8 figures; The 9th International Workshop on Tau-Lepton Physics, Tau0

High-statistics measurement of the pion form factor in the rho-meson energy range with the CMD-2 detector

We present a measurement of the pion form factor based on e+e- annihilation data from the CMD-2 detector in the energy range 0.6<sqrt(s)<1.0 GeV with a systematic uncertainty of 0.8%. A data sample is five times larger than that used in our previous measurement.Comment: 18 pages, 10 figures. Added comparison with KLOE measurement, minor updates. Accepted by PL

Observation of the conversion decay ϕ→π0e+e−\phi\to\pi^0e^+e^- at CMD-2

Using 15.1^{-1} of data collected by CMD-2 in the $\phi$-meson energy range, the branching ratio of the conversion decay $\phi\to\pi^0e^+e^-$ has been measured for the first time: B(\phi\to\pi^0e^+e^-) = (1.22 \pm 0.34 \pm 0.21) \cdot 10 ^{-5}.Comment: 13 pages, 6 PostScript figures, uses refmerge.sty. To be published in Phys. Lett.

Cross section of the reaction e+e−→π+π−π+π−e^+ e^- \to \pi^+\pi^-\pi^+\pi^- below 1 GeV at CMD-2

Using 3.07 ${pb}^{-1}$ of data collected in the energy range 0.60-0.97 GeV by CMD-2, about 150 events of the process \epm \to \pch have been selected. The energy dependence of the cross section agrees with the assumption of the $a_1(1260) \pi$ intermediate state which is dominant above 1 GeV. For the first time \fourpi events are observed at the $\rho$ meson energy. Under the assumption that all these events come from the $\rho$ meson decay, the value of the cross section at the $\rho$ meson peak corresponds to the following decay width: \Gamma(\rho^0 \to \fourpi) = (2.8 \pm 1.4 \pm 0.5) {keV} or to the branching ratio B(\rho^0 \to \fourpi) = (1.8 \pm 0.9 \pm 0.3) \cdot 10 ^{-5}.Comment: 15 pages, 5 figure

Marx generator GIN-1000 with 1 MV output voltage and 80 kJ stored energy

The results of development and study of Marx generator with output voltage of 1 MV and stored energy of 80 kJ are reported. The measured value of generator inductance is ~1.3 µH, the measured effective ohmic resistance ~ 1 Ohm.Приведены результаты разработки и исследования генератора Маркса с выходным напряжением 1 МВ, запасаемой энергией 80 кДж. Измеренное значение индуктивности генератора составляет ~1,3 мкГн, измеренное эффективное омическое сопротивление ~1 Ом.Наведено результати розробки і дослідження генератора Маркса з вихідною напругою 1 МВ, що запасає енергією 80 кДж. Виміряне значення індуктивності генератора становить ~1,3 мкГн, виміряний ефективний омічний опір ~1 Ом

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.