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Register a new userStudy of the process $e^+e^-toomegaetapi^0$ in the energy range $sqrt{s} <2$ GeV with the SND detector
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The process $e^+e^-toomegaetapi^0$ is studied in the energy range $1.45-2.00$ GeV using data with an integrated luminosity of 33 pb$^{-1}$ accumulated by the SND detector at the $e^+e^-$ collider VEPP-2000. The $e^+e^-toomegaetapi^0$ cross section is measured for the first time. The cross section has a threshold near 1.75 GeV. Its value is about 2 nb in the energy range $1.8-2.0$ GeV. The dominant intermediate state for the process $e^+e^- to omegaetapi^0$ is found to be $omega a_0(980)$.
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The process $e^+e^-toetapi^0gamma$ is studied in the center-of-mass energy range 1.05-2.00 GeV using data with an integrated luminosity of 94.5 pb$^{-1}$ collected by the SND detector at the VEPP-2000 $e^+e^-$ collider. The $e^+e^-toetapi^0gamma$ cross section is measured for the first time. It is shown that the dominant mechanism of this reaction is the transition through the $omegaeta$ intermediate state. The measured cross section of the subprocess $e^+e^-toomegaetatoetapi^0gamma$ is consistent with previous measurements in the $e^+e^-topi^+pi^-pi^0eta$ mode. It is found, with a significance of 5.6$sigma$, that the process $e^+e^-toetapi^0gamma$ is not completely described by hadronic vector-pseudoscalar intermediate states. The cross section of this missing contribution, which can originate from radiation processes, e. g. $e^+e^-to a_{0}(1450)gamma$, is measured. It is found to be 15-20 pb in the wide energy range from 1.3 to 1.9 GeV.
The review of the SND results of the $e^+e^-topi^+pi^-pi^0$ process study in the energy range $sqrt[]{s}=0.42$ -- 1.38 GeV at VEPP-2M collider, based on about $2times 10^6$ selected events, is presented. The total cross section, parameters of the $rho$, $omega$, $phi$ resonances, and $omega^prime$, $omega^{primeprime}$ states were obtained. It was found that $rhopi$ and $omegapi^0$ intermediate states describe the reaction dynamics. The experimental data cannot be described by a sum of only $omega$, $phi$, $omega^prime$ and $omega^{primeprime}$ resonances contributions. This can be interpreted as a manifestation of the $rhoto 3pi$ decay, suppressed by $G$-parity, with relative probability $B(rhoto 3pi) = (1.01pm^{0.54}_{0.36}pm 0.034) times 10^{-4}$.
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: $m_omega=782.79pm 0.08pm 0.09$ MeV, $Gamma_omega=8.68pm 0.04pm 0.15$ MeV and $sigma(omegato 3pi)=1615pm 9pm 57$ nb were obtained. It was found that the experimental data cannot be described by a sum of only $omega$, $phi$, $omega^prime$ and $omega^{primeprime}$ resonances contributions. This can be interpreted as a manifestation of $rhoto 3pi$ decay, suppressed by $G$-parity, with relative probability $B(rhoto 3pi) = (1.01pm^{0.54}_{0.36}pm 0.034) times 10^{-4}$.
New results of the e+e- -> pi+pi-, K+K-, K_SK_L, pi0/gamma, eta0/gamma processes cross section measurements are presented. The results are based on the 30 pb^-1 data, accumulated by SND detector at VEPP-2M e+e- collider in the energy range sqrt(s)=0.4-1.4 GeV during 1995-2000 years. The comparison with existing experimental data shows that the measurement accuracy is close to or better than the world average. For the e+e- -> pi+pi- process the accuracy is about 0.01. This is important for calculation of hadronic contribution into the muon anomalous magnetic moment.
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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