Electron-Positron Interactions at High Energies

Abstract

The results of an experiment performed at Adone, the 2×1.5-GeV $e^{+}{e}^{-}$ Frascati storage ring, are presented. During ∼ 1500 hours of running time a total of 5164 electron-positron elastic scattering events (integrated luminosity $\mathcal{L}=3.5\mathrm{}\times {10}^{35}$ ${\mathrm{cm}}^{-2\mathrm{}}$) and 605 noncoplanar events from the reaction $e^{+}{e}^{-}\to a^{\pm }+b^{\pm }+\mathrm{anything}$ (effective integrated luminosity $\mathcal{L}=2.5\mathrm{}\times {10}^{35}$ ${\mathrm{cm}}^{-2\mathrm{}}$) have been collected at c.m. energies ranging from 1.4 to 2.4 GeV. Over the energy range explored (1.4-2.4 GeV), corresponding to an average $q^2$ ranging from 0.8 to 2.4 ${(\mathrm{G}\mathrm{e}\mathrm{V}/\mathit{c})}^2$, the yield of wide-angle ($60°<\theta <120\mathrm{}°$) electron-positron elastic scattering events is found to be in good agreement with the predictions of quantum electrodynamics (QED) ($R=\frac{{\sigma }_{\exp }}{{\sigma }_{\mathrm{QED}}}=1.05\mathrm{}\pm 0.04$). The noncoplanar events appear to be of a hadronic nature and are produced with a much higher cross section than predicted on the basis of $\rho$, $\omega$, $\phi$ dominance at these energies. The total cross section for the reaction $e^{+}{e}^{-}\to a^{\pm }{b}^{\pm }+\mathrm{anything}$ shows a rapid increase to ∼ 90 nb between 1.0 and 1.5 GeV and falls off slowly to ∼ 50 nb at 2.4 GeV. Cross sections for some of the channels contributing to this multihadron process ($e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}$, $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^{+}{\pi }^{-}+\mathrm{neutrals}$, $e^{+}{e}^{-}\to 3{\pi }^{+}3{\pi }^{-}$) have been determined and are reported.