Abstract
The e+e−→π+π−π+π− cross section has been measured using 5.8 pb−1 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%.
Highlights
Production of four pions in e+e− annihilation is the dominant process contributing to the total hadronic cross section in the c.m. energy range between 1000 and 2000 MeV
For four-track events the remaining background is estimated to be less than 1%
The three-track events used in this analysis allowed a significant increase of the data sample and improvement of the systematic uncertainties
Summary
Production of four pions in e+e− annihilation is the dominant process contributing to the total hadronic cross section in the c.m. energy range between 1000 and 2000 MeV. With ω and η decays to π+π−π0), which results in a lower total energy because of a missing π0 To obtain the number of four-pion events from a three-track sample, the distribution shown in Fig. 3(b) was fit with a sum of functions describing a pion peak and background. Some energy-dependent contribution to the total experimental uncertainty is possible below 1100 MeV, but there the systematic error is much smaller than a statistical one
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