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Register a new userStudy of the process $e^+e^-{to}K^+K^-eta$ with the CMD-3 detector at the VEPP-2000 collider
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The process $e^+e^-{to}K^+K^-eta$ has been studied in the center-of-mass energy range from 1.59 to 2.007,GeV using the data sample of 59.5 pb$^{-1}$, collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider in 2011, 2012 and 2017. The $K^+K^-eta$ final state is found to be dominated by the contribution of the $phi(1020)eta$ intermediate state. The cross section of the process $e^+e^-{to}phi(1020)eta$ has been measured with a systematic uncertainty of 5.1$%$ on the base of 3009 $pm$ 67 selected events. The obtained cross section has been used to calculate the contribution to the anomalous magnetic moment of the muon: $a_{mu}^{phieta}(E<1.8, {rm GeV})=(0.321 pm 0.015_{rm stat} pm 0.016_{rm syst}) times 10^{-10}$, $a_{mu}^{phieta}(E<2.0, {rm GeV})=(0.440 pm 0.015_{rm stat} pm 0.022_{rm syst}) times 10^{-10}$. From the cross section approximation the $phi(1680)$ meson parameters have been determined with better statistical precision, than in previous studies.
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The process $e^+e^- to K^+K^-pi^+pi^-$ has been studied in the center-of-mass energy range from 1500 to 2000,MeV using a data sample of 23 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider. Using about 24000 selected events, the $e^+e^- to K^+K^-pi^+pi^-$ cross section has been measured with a systematic uncertainty decreasing from 11.7% at 1500-1600,MeV to 6.1% above 1800,MeV. A preliminary study of $K^+K^-pi^+pi^-$ production dynamics has been performed.
The process e+ e- -> phi -> K+ K- has been studied with the CMD-2 detector using about 542 000 events detected in the center-of-mass energy range from 1.01 to 1.034 GeV. The systematic error of the cross section is estimated to be 2.2%. The phi(1020) meson parameters in the phi -> K+K- decay channel have been measured: sigma_0(phi-> K+K-) = 2016 +- 8 +- 44 nb, m(phi) = 1019.441 +- 0.008 +- 0.080 MeV/c2, Gamma(phi) = 4.24 +- 0.02 +- 0.03 MeV, B(e+e-)B(K+K-) = (14.27 +- 0.05 +- 0.31)*10(-5).
The cross section of the process $e^{+}e^{-}rightarrowetapi^{+}pi^{-}$ is measured using the data collected with the CMD-$3$ detector at the VEPP-$2000$ collider in the center-of-mass energy range from $1.1$ to $2.0$ GeV. The decay mode $etarightarrowgammagamma$ is used for $eta$ meson reconstruction in the data sample corresponding to an integrated luminosity of $78.3$ pb$^{-1}$. The energy dependence of the $e^{+}e^{-}rightarrowetapi^{+}pi^{-}$ cross section is fitted within the framework of vector meson dominance in order to extract the $Gamma(rho(1450)rightarrow{^{+}e^{-}})mathcal{B}(rho(1450)rightarrowetapi^{+}pi^{-})$ and the $Gamma(rho(1700)rightarrow{e^{+}e^{-}})mathcal{B}(rho(1700)rightarrowetapi^{+}pi^{-})$ products. Based on conservation of vector current, the analysed data are used to test the relationship between the $e^{+}e^{-}rightarrowetapi^{+}pi^{-}$ cross section and the spectral function in $tau^-rightarrowetapi^-pi^0 u_tau$ decay. The $e^{+}e^{-}rightarrowetapi^{+}pi^{-}$ cross section measured with the CMD-$3$ detector is in good agreement with the previous measurements.
A search for the rare decay $eta^{prime} to e^+e^-$ has been performed with the SND detector at the VEPP-2000 $e^+e^-$ collider. The inverse reaction $e^+e^- to eta^{prime}$ and $eta^{prime}$ five decay chains have been used for this search. The upper limit $Gamma_{eta^{prime} to e^+e^-}<0.002$ eV at the 90% confidence level has been set. A sensitivity of SND in a search for $eta to e^+e^-$ decay has been studied. For this perpose we have analyzed a data sample with an integrated luminosity of 108 nb$^{-1}$ collected in the center-of-mass energy range 520-580 MeV. There are no background events for the reaction $e^+e^- to eta$ with decay $eta to pi^0pi^0pi^0$ have been found. In the absence of background, a sensitivity to $B(eta to e^+e^-)$ of 10$^{-6}$ can be reached during two weeks of VEPP-2000 operation.
In experiment with the SND detector at VEPP-2M $e^+e^-$ collider the $e^+e^-toetagamma$ cross section was measured in the energy range $E$=0.60--1.38 GeV with the integrated luminosity of 27.8 pb$^{-1}$. The measured cross section is well described by the vector meson dominance model with contributions from the $rho(770)$, $omega(783)$, $phi(1020)$, $rho^{prime}(1465)$ resonances and agrees with results of previous measurements. The decay probabilities $BR(phitoetagamma)$, $BR(omegatoetagamma)$ and $BR(rhotoetagamma)$ were measured with the accuracies better than or comparable to the world averages.
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