Measurement of InclusiveηProduction ine+e−Interactions near Charm Threshold

Abstract

We have measured the inclusive cross section for $\eta$ production in $e^{+}{e}^{-}$ interactions near charm threshold using the Crystal Ball detector. No pronounced structure in the energy dependence is observed. By comparing cross sections above and below charm threshold we obtain the limits (90% confidence limit): $R(e^{+}{e}^{-}\to F\overline{F}X)R_B(F\to \eta x)<\mathrm{}0.15-0.32\mathrm{}$ (for $E_{\mathrm{c}.\mathrm{m}.\mathrm{}}$ from 4.0 to 4.5 GeV), $R_B(D\to \eta x)<\mathrm{}0.13\mathrm{}$. Our results are inconsistent with a previous report of a large energy dependence of the $\eta$ cross section ascribed to the crossing of the $F{F}^{*}$ and $F^{*}{F}^{*}$ production thresholds.