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تسجيل مستخدم جديدUpdate of the e^+e^-topi^+pi^- cross section measured by SND detector in the energy region 400<sqrt{s}<1000 MeV
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The corrected cross section of the e^+e^-topi^+pi^- process measured in the SND experiment at the VEPP-2M e^+e^- collider is presented. The update is necessary due to a flaw in the e^+e^-topi^+pi^- and e^+e^-tomu^+mu^- Monte Carlo events generators used previously in data analysis.
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The cross section of the process e^+e^-to pi^+pi^- was measured in the SND experiment at the VEPP-2M collider in the energy region 400<sqrt[]{s}<1000 MeV. This measurement was based on about 12.4 times 10^6 selected collinear events, which include 7.
4times 10^6 e^+e^-to e^+e^-, 4.5times 10^6 e^+e^-topi^+pi^- and 0.5times 10^6 e^+e^-tomu^+mu^- selected events. The systematic uncertainty of the cross section determination is 1.3 %. The rho-meson parameters were determined: m_rho=774.9pm 0.4pm 0.5 MeV, Gamma_rho=146.5pm 0.8pm 1.5 MeV, sigma(rhotopi^+pi^-)=1220pm 7pm 16 nb as well as the parameters of the G-parity suppressed decay omegatopi^+pi^-: sigma(omegatopi^+pi^-)=29.9pm 1.4pm 1.0 nb and phi_{rhoomega} = 113.5pm 1.3pm 1.7 degree.
The cross section of the process $e^+ e^-topi^+pi^-$ has been measured in the Spherical Neutral Detector (SND) experiment at the VEPP-2000 $e^+e^-$ collider VEPP-2000 in the energy region $525 <sqrt[]{s} <883$ MeV. The measurement is based on data wi
th an integrated luminosity of about 4.6 pb$^{-1}$. The systematic uncertainty of the cross section determination is 0.8 % at $sqrt{s}>0.600$ GeV. The $rho$ meson parameters are obtained as $m_rho = 775.3pm 0.5pm 0.6$ MeV, $Gamma_rho = 145.6pm 0.6pm 0.8$ MeV, $B_{rhoto e^+ e^-}times B_{rhotopi^+pi^-} = (4.89pm 0.02pm 0.04)times 10^{-5}$, and the parameters of the $e^+ e^-toomegatopi^+pi^-$ process, suppressed by $G$-parity, as $B_{omegato e^+ e^-}times B_{omegatopi^+pi^-}= (1.32pm 0.06pm 0.02)times 10^{-6} $ and $phi_{rhoomega} = 110.7pm 1.5pm1.0$ degrees.
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 $rh
o$, $omega$, $phi$ 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 process $e^+e^-to K^+K^-pi^0$ is studied with the SND detector at the VEPP-2000 $e^+e^-$ collider. Basing on data with an integrated luminosity of 26.4~pb$^{-1}$ we measure the $e^+e^-to K^+K^-pi^0$ cross section in the center-of-mass energy rang
e from 1.28 up to 2 GeV. The measured mass spectrum of the $Kpi$ system indicates that the dominant mechanism of this reaction is the transition through the $K^{ast}(892)K$ intermediate state. The cross section for the $phipi^0$ intermediate state is measured separately. The SND results are consistent with previous measurements in the BABAR experiment and have comparable accuracy. We study the effect of the interference between the $phipi^0$ and $K^ast K$ amplitudes. It is found that the interference gives sizable contribution to the measured $e^+e^- to phi pi^0to K^+K^-pi^0$ cross section below 1.7 GeV.
The process $e^+e^- to pi^+pi^-pi^0eta$ is studied in the center-of-mass energy region below 2 GeV with the SND detector at the VEPP-2000 $e^+e^-$ collider. The four intermediate states contribute to this process: $omegaeta$, $phieta$, $a_0(980)rho$,
and a structureless $pi^+pi^-pi^0eta$ state. We measure the total $e^+e^- to pi^+pi^-pi^0eta$ cross section and the cross sections for its components: $omegaeta$, $phieta$, and a sum of $a_0(980)rho$ and the structureless state. Our results are in agreement with previous measurements and have comparable or better accuracies.
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