| Summary: | We present a measurement of the ratio of the tt̅ production cross section via gluon-gluon fusion to the total tt̅ production cross section in pp̅ collisions at √s=1.96 TeV at the Tevatron. Using a data sample with an integrated luminosity of 955 pb[superscript -1] recorded by the CDF II detector at Fermilab, we select events based on the tt̅ decay to lepton+jets. Using an artificial neural network technique we discriminate between tt̅ events produced via qq̅ annihilation and gg fusion, and find Gf=σ(gg→tt̅ )/σ(pp̅ →tt̅ )<0.33 at the 68% confidence level. This result is combined with a previous measurement to obtain the most stringent measurement of this quantity by CDF to date, Gf=0.07[subscript -0.07][superscript +0.15].
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