The cross section of the process e+e- -> pi+pi- has been measured at the CMD-2 detector in the 370-520 MeV center-of-mass (c.m.) energy range. A systematic uncertainty of the measurement is 0.7 %. Using all CMD-2 data on the pion form factor, the pion electromagnetic radius was calculated. The cross section of muon pair production was also determined.
A cross section of the process $e^+e^- to pipipipi$ has been measured using 6798$pm$93 signal events from a data sample corresponding to an integrated luminosity of 9.8 pb$^{-1}$ collected with the CMD-3 detector in the center-of-mass energy range 920--1060 MeV. The measured cross section exhibits an interference pattern of the $phi(1020)topipipipi$ decay with a non-resonant process $e^+e^- to pipipipi$, from which we obtain the branching fraction of the doubly suppressed decays (by G-parity and OZI rule): $BR(phitopipipipi) = (6.5pm2.7pm1.6)times 10^{-6}$.
The cross section of the process e+e- -> pi+pi- has been measured using about 114000 events collected by the CMD-2 detector at the VEPP-2M e+e- collider in the center-of-mass energy range from 0.61 to 0.96 GeV. Results of the pion form factor determination with a 0.6% systematic uncertainty are presented. Implications for the hadronic contribution to the muon anomalous magnetic moment are discussed.
The e+e- -> pi+pi-pi+pi- cross section has been measured using 5.8/pb of integrated luminosity collected with the CMD-2 detector at the VEPP-2M collider. Analysis of the data with a refined efficiency determination and use of both three- and four-track events allowed doubling of a data sample and reduction of systematic errors to 5-7%.
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 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.
R.R.Akhmetshin
,V.M.Aulchenko
,V.Sh.Banzarov
.
(2006)
.
"Measurement of the e+e- -> pi+pi- cross section with the CMD-2 detector in the 370-520 MeV c.m. energy range"
.
Alexei Sibidanov
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