This paper reports a measurement of the cross section for the
pair production of top quarks in p anti-p collisions at s**(1/2) ñ.96
TeV at the Fermilab Tevatron. The data was collected from the CDF Run II
detector in a set of runs with a total integrated luminosity of 1.1 fb-1.
The cross section is measured in the dilepton channel, the subset of t
anti-t events in which both top quarks decay through t --> Wb -->
l nu b, where l þ, mu, or tau. The lepton pair is reconstructed as
one identified electron or muon and one isolated track. The use of
an isolated track to identify the second lepton increases the tt-bar
acceptance, particularly for the case in which one W decays as W -->
tau nu. The purity of the sample may be further improved at the cost of
a reduction in the number of signal events, by requiring an identified
b-jet. We present the results of measurements performed with and without
the request of an identified b-jet. The former is the first published CDF
result for which a b-jet requirement is added to the dilepton selection.
In the CDF data there are 129 pretag lepton + track candidate events, of
which 69 are tagged. With the tagging information, the sample is divided
into tagged and untagged sub-samples, and a combined cross section is
calculated by maximizing a likelihood. The result is sigma_tt-bar ù.6
+/- 1.2(stat.)+0.6_-0.5(sys.) +/- 0.6(lum.) pb, assuming a branching
ratio of BR( W --> l nu) ñ0.8% and a top mass of m_t ñ75 GeV/c2.
Return to top of page.
Go to Physics Results
Updated: Tuesday, 2009 July 07 12:54:48 CDT automatically from input from carol picciolo