First measurement of the fraction of top-quark pair production through gluon-gluon fusion

Abstract

We present the first measurement of $\ensuremath{\sigma}(gg\ensuremath{\rightarrow}t\overline{t})/\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}t\overline{t})$. We use $0.96\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of $\sqrt{s}=1.96\text{ }\text{ }\mathrm{TeV}$ $p\overline{p}$ collision data recorded with the CDF II detector at Fermilab. Using charged particles with low transverse momentum in $t\overline{t}$ events, we find $\ensuremath{\sigma}(gg\ensuremath{\rightarrow}t\overline{t})/\ensuremath{\sigma}(p\overline{p}\ensuremath{\rightarrow}t\overline{t})=0.07\ifmmode\pm\else\textpm\fi{}0.14(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.07(\mathrm{syst})$, corresponding to a 95% confidence level upper limit of 0.33, in agreement with the standard model next-to-leading-order prediction of $0.15\ifmmode\pm\else\textpm\fi{}0.05$.