Measurement of e+e- -> pi+pi- cross section with CMD-2 around rho(770) meson

TL;DR

This paper reports a precise measurement of the e+e- to pi+pi- cross section around the rho(770) meson using CMD-2, providing detailed parameters of the rho and rho-omega interference with minimal systematic error.

Contribution

It presents new high-precision measurements of the pion form factor and rho-meson parameters in e+e- collisions, improving accuracy over previous results.

Findings

Measured rho-meson mass as 775.28 MeV

Determined rho width as 147.70 MeV

Found rho-e+e- decay width as 6.93 keV

Abstract

In experiments with the CMD-2 detector at the VEPP-2M electron-positron collider at Novosibirsk about 150000 $e^+e^-\to\pi^+\pi^-$ events were recorded in the center-of-mass energy range from 0.61 up to 0.96 GeV. The result of the pion form factor measurement with a 1.4% systematic error is presented. The following values of the $\rho$-meson and $\rho-\omega$ interference parameters were found: $M_\rho=(775.28\pm 0.61\pm 0.20) MeV, \Gamma_\rho=(147.70\pm 1.29 \pm 0.40) MeV, \Gamma(\rho\to e^+e^-)=(6.93\pm 0.11\pm 0.10) keV, Br(\omega\to\pi^+\pi^-) = (1.32\pm 0.23)%$.