Measurement of the ratio σtt̄/σZ/γ*→ll and precise extraction of the tt̄ cross section

Abstract

We report a measurement of the ratio of the tt̄ to Z/γ*production cross sections in √s=1.96TeV pp̄ collisions using data corresponding to an integrated luminosity of up to 4.6fb-1, collected by the CDF II detector. The tt̄ cross section ratio is measured using two complementary methods, a b-jet tagging measurement and a topological approach. By multiplying the ratios by the well-known theoretical Z/γ*→ll cross section predicted by the standard model, the extracted tt̄ cross sections are effectively insensitive to the uncertainty on luminosity. A best linear unbiased estimate is used to combine both measurements with the result σtt̄=7.70±0.52pb, for a top-quark mass of 172.5GeV/c2. © 2010 The American Physical Society.