Measurement of the fraction of t-tbar production via gluon-gluon fusion in p-pbar collisions at sqrt(s)=1.96 TeV

We present a measurement of the ratio of t-tbar production cross section via gluon-gluon fusion to the total t-tbar production cross section in p-pbar collisions at sqrt{s}=1.96 TeV at the Tevatron. Using a data sample with an integrated luminosity of 955/pb recorded by the CDF II detector at Fermilab, we select events based on the t-tbar decay to lepton+jets. Using an artificial neural network technique we discriminate between t-tbar events produced via q-qbar annihilation and gluon-gluon fusion, and find Cf=(gg->ttbar)/(pp->ttbar)<0.33 at the 68% confidence level. This result is combined with a previous measurement to obtain the most precise measurement of this quantity, Cf=0.07+0.15-0.07.Comment: submitted to Phys. Rev.

Measurement of the fraction of t(t)over-bar production via gluon-gluon fusion in p(p)over-bar collisions at root s=1.96 Tev

We present a measurement of the ratio of the t (t) over bar production cross section via gluon-gluon fusion to the total t (t) over bar production cross section in p (p) over bar collisions at root s = 1.96 Tev at the Tevatron. Using a data sample with an integrated luminosity of 955 pb(-1) recorded by the CDF II detector at Fermilab, we select events based on the t (t) over bar decay to lepton + jets. Using an artificial neural network technique we discriminate between t (t) over bar events produced via q (q) over bar annihilation and gg fusion, and find G(f) = sigma(gg -&gt; t (t) over bar/sigma(p (p) over bar -&gt; t (t) over bar) &lt; 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, G(f) = 0.07(-0.07)(+0.15)