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Observed! March 5, 2009

Posted by gordonwatts in physics.

Check it out:

Abstract: We report first observation of the electroweak production of single top quarks in ppbar collisions at sqrt(s) = 1.96 TeV based on 2.3 fb^-1 of data collected by the D0 detector at the Fermilab Tevatron Collider. Using events containing an isolated electron or muon and missing transverse energy, together with jets originating from the fragmentation of b quarks, we measure a cross section of sigma(ppbar -> tb + X, tqb + X) = 3.94 +- 0.88 pb. The probability to measure a cross section at this value or higher in the absence of signal is 2.5 x 10^-7, corresponding to a 5.0 standard deviation significance for the observation.

I don’t think it was 5 years in the making – but close to that. Congratulations to everyone involved, and there were a lot of people.

I and my students and post-doc were intimately involved in the evidence paper, but this one I was mostly looking in the from the outside. But getting to 5 sigma was definitely harder than our earlier 3 sigma result. I can’t tell you how happy I am that this result has been submitted to the journals! Excellent!

Update: And CDF got it too – a joint discovery!

We report observation of single top quark production using 3.2 fb1 of pp collision data with ps = 1:96 TeV collected by the Collider Detector at Fermilab. The signicance of the observed data is 5.0 standard deviations, and the expected sensitivity is in excess of 5.9 standard deviations. We measure a cross section of 2:3+0:6-0:5(stat + syst) pb, extract the CKM matrix element value|Vtb|= 0:91+0:11-0:11(stat + syst)  0:07(theory), and set the limit |Vtb|> 0:71 at the 95% C.L.


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