Study of the process $e^+e^- \to \pi^+\pi^-$ in the energy region 400<\sqrt[]{s}<1000 MeV

TL;DR

This paper reports precise measurements of the e^+e^- to pi^+pi^- cross section in the 400-1000 MeV energy range, determining rho-meson parameters and decay characteristics with high accuracy.

Contribution

The study provides new, highly accurate measurements of the e^+e^- to pi^+pi^- cross section and rho-meson parameters in the specified energy region, improving previous data.

Findings

Measured cross section with 1.3% systematic uncertainty

Determined rho-meson mass and width with high precision

Extracted parameters of the omega to pi+pi- decay

Abstract

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 7.4\times 10^6 e^+e^-\to e^+e^-, 4.5\times 10^6 e^+e^-\to\pi^+\pi^- and 0.5\times 10^6 e^+e^-\to\mu^+\mu^- selected events. The systematic uncertainty of the cross section determination is 1.3 %. The \rho-meson parameters were determined: m_\rho=774.9\pm 0.4\pm 0.5 MeV, \Gamma_\rho=146.5\pm 0.8\pm 1.5 MeV, \sigma(\rho\to\pi^+\pi^-)=1220\pm 7\pm 16 nb as well as the parameters of the G-parity suppressed decay \omega\to\pi^+\pi^-: \sigma(\omega\to\pi^+\pi^-)=29.9\pm 1.4\pm 1.0 nb and \phi_{\rho\omega} = 113.5\pm 1.3\pm 1.7 degree.