Search for the flavor changing neutral current decay <I>t &rarr; Zq</I> at <I>&radic;s</I> = 1.96 TeV

Thesis (Ph. D.)--University of Rochester. Dept. of Physics and Astronomy, 2009.This thesis reports the results of a search for the flavor changing neutral current decay of the top quark, t → Zq, in decays of t[bar over t] pairs produced in p[bar over p] collisions at a center-of-mass energy of 1.96 TeV. This search is performed on a data sample recorded by the Collider Detector at Fermilab (CDF), corresponding to an integrated luminosity of 1.9 fb−1. This search follows a previous CDF analysis that resulted in an upper limit for the branching fraction B(t → Zq) of 10.4% at 95% C.L. using a dataset equivalent to 1.1 fb−1 of integrated luminosity. This thesis extends to 1.9 fb−1 of data, and has improved sensitivity to the small signal with the introduction of a template fit technique that includes systematic uncertainties by a linear interpolation between templates. Using a Feldman-Cousins construction, an upper limit at 95% C.L. is set on B(t → Zq) of 3.7%, with the expected upper limit in absence of a signal is 5.0 ± 2.2% for a top mass of 175 GeV/c2