  We present the first measurement of the fraction of top quark pair production
through gluon-gluon fusion. We use 0.96/fb of s**(1/2)=1.96 TeV p-pbar
collision data recorded with the CDF II detector at Fermilab. We identify the
candidate t-tbar events with a high-energy charged lepton, a neutrino
candidate, and four or more jets. Using charged particles with low transverse
momentum in t-tbar events, we find the fraction of top quark pair production
through gluon-gluon fusion to be 0.07+/-0.14(stat)+/-0.07(syst), corresponding
to a 95% confidence level upper limit of 0.33, in agreement with the standard
model NLO prediction of 0.15+/-0.05.
