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Title
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Search for the neutral current top quark decay using the ratio of Z-boson+4 jets to W-boson+4 jets production
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Author
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Institution/Organisation
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CDF Collaboration
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Abstract
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| We have used the Collider Detector at Fermilab (CDF-II) to search for the flavor-changing neutral-current (FCNC) top-quark decay t→Zc using a technique employing ratios of W and Z production, measured in pp̅ data corresponding to an integrated luminosity of 1.52 fb-1. The analysis uses a comparison of two decay chains, pp̅ →tt̅ →WbWb→ℓνbjjb and pp̅ →tt̅ →ZcWb→ℓℓcjjb, to cancel systematic uncertainties in acceptance, efficiency, and luminosity. We validate the modeling of acceptance and efficiency for lepton identification over the multiyear data set using another ratio of W and Z production, in this case the observed ratio of inclusive production of W to Z bosons. To improve the discrimination against standard model backgrounds to top-quark decays, we calculate the top-quark mass for each event with two leptons and four jets assuming it is a tt̅ event with one of the top quarks decaying to Zc. For additional background discrimination we require at least one jet to be identified as originating from a b quark. No significant signal is found and we set an upper limit on the FCNC branching ratio Br(t→Zc) using a likelihood constructed from the ℓℓcjjb top-quark mass distribution and the number of ℓνbjjb events. Limits are set as a function of the helicity of the Z boson produced in the FCNC decay. For 100% longitudinally-polarized Z bosons we find limits of 8.3% and 9.3% (95% C.L.) depending on the assumptions regarding the theoretical top-quark pair production cross section. |
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Language
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English
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Source (journal)
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Physical review : D : particles, fields, gravitation, and cosmology / American Physical Society. - Ridge, N.Y., 2004 - 2015
Physical review : D : particles and fields. - Lancaster, Pa, 1970 - 2003
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Publication
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Ridge, N.Y.
:
American Physical Society
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2009
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ISSN
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1550-7998
[print]
1550-2368
[online]
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Volume/pages
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80
:5
(2009)
, p. 052001,1-052001,24
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ISI
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000270384900012
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Full text (Publisher's DOI)
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Full text (open access)
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