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

TL;DR

This paper measures the proportion of top-antitop pairs produced via gluon-gluon fusion at the Tevatron, using neural networks to distinguish production mechanisms and combining results for the most precise estimate.

Contribution

It introduces a neural network-based method to differentiate between production mechanisms of top pairs and provides the most precise measurement of gluon-gluon fusion contribution.

Findings

Cf<0.33 at 68% confidence level

Combined measurement yields Cf=0.07+0.15-0.07

Uses 955/pb data from CDF II detector

Abstract

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.