Title
Search for the neutral current top quark decay <tex>$t\rightarrow Zc$</tex> using the ratio of Z-boson+4 jets to W-boson+4 jets production Search for the neutral current top quark decay <tex>$t\rightarrow Zc$</tex> using the ratio of Z-boson+4 jets to W-boson+4 jets production
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
Lancaster, Pa ,
Subject
Physics
Source (journal)
Physical review : D : particles and fields. - Lancaster, Pa, 1970 - 2003
Volume/pages
80(2009) :5 , p. 052001,1-052001,24
ISSN
0556-2821
ISI
000270384900012
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
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 pp&#773; data corresponding to an integrated luminosity of 1.52  fb-1. The analysis uses a comparison of two decay chains, pp&#773; →tt&#773; →WbWb→&#8467;νbjjb and pp&#773; →tt&#773; →ZcWb→&#8467;&#8467;cjjb, 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 tt&#773; 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 &#8467;&#8467;cjjb top-quark mass distribution and the number of &#8467;νbjjb 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.
Full text (open access)
https://repository.uantwerpen.be/docman/irua/ba75d2/4b4ca93b.pdf
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