Top Production Properties at the Tevatron Page: 4 of 4
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(- = 1.7+0.3pb) and W* production (- = 0.7t0.lpb ). Whereas the study of ti pair production
tells us about the strong interaction of the top quark, single top production can help us learn
about the electroweak interactions of the top quark because of the Wtb coupling. The single
top cross section is proportional to I'(t - Wb) which is proportional to the square of the Vt6
CKM matrix element. Thus a measurement of -(single top) can be used to determine Vtl
without assuming a unitary three generation CKM matrix as other measurements have done. If
the Vtb measurement is very different from unity, it could indicate non-SM physics such as a
A measurement of the single top cross section is difficult because of the small cross section
and the large W + two jets QCD backgrounds (Wbb, Wcc). A CDF analysis has used the lepton
+ jets channel.9 It requires Mlvb to be near Mto, and fits the Ht distribution (Et sum over jets,
lepton, and missing ET in event) to the expected QCD background, tt background, and single
top signal. The expected background is much larger than the expected signal, so the cross section
is not measured from Run 1 data. Rather, an upper limit on the cross section is determined.
The preliminary CDF (DO) 95% CL upper limit (both processes combined) is 13.5 pb (47 pb).
With the acquisition of an SVX for Run 2, the DO measurement should be competitive with
CDF. Run 1 limits are much higher than the standard model prediction of ~2.4 pb. Neural net
analyses are in progress in an attempt to handle the large backgrounds. In Run 2 it is hoped to
measure the single top cross section to a precision of about (20-30)%.
The discovery of the top quark in Run 1 at the Fermilab Tevatron was a great success. The
studies on the small number of top events available in Run 1 data included measurements of
the ti cross section, the ti invariant mass spectrum, the top quark PT distribution, and single
top production. There has been no evidence for non-Standard Model physics. Because of a
factor twenty increase in luminosity and upgraded detectors, there will be a greater potential to
discover new physics in Run 2 with higher precision top quark studies.
This work was made possible by the support of the members of the CDF and DO collaborations
and by the U.S. Department of Energy (grant DE-FG02-91ER40685).
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the proceedings of 13th Les Rencontres de Physique de la Valle d'Aoste. hep-ex/9909016
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Vaiciulis, Anthony. Top Production Properties at the Tevatron, article, December 11, 2000; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc715256/m1/4/: accessed April 26, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.