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arxiv: hep-ex/9912020 · v1 · pith:3GLVIRIHnew · submitted 1999-12-10 · ✦ hep-ex

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

classification ✦ hep-ex
keywords crossenergyeventsfourpimesonsectionassumptioncmd-2
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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}.

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