We report the observation of electroweak single top quark
production in 3.2 fb-1 of p anti-p collision data collected by the
Collider Detector at Fermilab at s**(1/2) ñ.96 TeV. Candidate events in
the W+jets topology with a leptonically decaying W boson are classified
as signal-like by four parallel analyses based on likelihood functions,
matrix elements, neural networks, and boosted decision trees.
These results are combined using a super discriminant analysis
based on genetically evolved neutral networks in order to improve
the sensitivity. This combined result is further combined with that
of a search for a single top quark signal in an orthogonal sample of
events with missing transverse energy plus jets and no charged lepton.
We observe a signal consistent with the standard model prediction but
inconsistent with the background-only model by 5.0 standard deviations,
with a median expected sensitivity in excess of 5.9 standard deviations.
We measure a production cross section of 2.3-.06_-0.5(stat + sys) pb,
extract the CKM matrix element value |V(tb)| ð.91+0.11_-0.11(stat + sys)
+/- 0.07(theory), and set a lower limit |V(tb)| > 0.71 at the 95%
confidence level, assuming m_t ñ75 GeV/c2.
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Updated: Friday, 2010 December 17 09:30:02 CST automatically from input from Carol Picciolo