Study of the process e + e − → π+π− in the energy region $$400 < \sqrt s < 1000 MeV^\P $$

Abstract

The cross section of the process e + e − → π+π− was measured in the spherical neutral detector experiment at the VEPP-2M collider in the energy region $$400 < \sqrt s < 1000 MeV$$ . This measurement was based on about 12.4 × 106 selected collinear events, which include 7.4 × 106 e + e − → e + e −, 4.5 × 106 e + e − → π+π−, and 0.5 × 106 e + e − → μ+μ− selected events. The systematic uncertainty of cross section determination is 1.3%. The ρ-meson parameters were determined as m ρ = 774.9±0.4±0.5 MeV, Γ ρ = 146.5±0.8±1.5 MeV, and σ(ρ → π+π−) = 1220 ± 7 ± 16 nb and the parameters of the G-parity suppressed decay ω → π+π− as σ(ω → π+π−) = 29.9 ± 1.4 ± 1.0 nb and φρω = 113.5±1.3±1.7°.