The first direct limit on the $t$ quark lifetime
Abstract
This dissertation presents the first direct limit on the t quark lifetime, measured in $t\bar{t}$ pair production candidate events from a 318 pb-1 sample of $p +\bar{p}$ collisions recorded by the Collider Detector at Fermilab (CDF). Candidate events are identified by a leptonically decaying W± boson and three or more jets, at least one of which contains a secondary vertex. In each event we measure the transverse track-to-beam displacement (impact parameter) of the lepton from the W± decay, and compare the distribution to templates constructed from $t\bar{t}$ event simulations with a variable t lifetime. Anticipated background distributions are measured with a combination of Monte Carlo event simulation and control samples, and included in the templates. We determine the following limits: cτt < 52.5µm @ 95% C.L. cτt < 43.5µm @ 90% C.L. We thus conclude that the top mean lifetime is less than 145 fs (175 fs) at 90% (95%) C.L.