A measurement of the top quark mass in the dilepton decay channel at CDF II.

Abstract

The top quark, the most recently discovered quark, is the most massive known fundamental fermion. Precision measurements of its mass, a free parameter in the Standard Model of particle physics, can be used to constrain the mass of the Higgs Boson. In addition, deviations in the mass as measured in different channels can provide possible evidence for new physics. We describe a measurement of the top quark mass in the decay channel with two charged leptons, known as the dilepton channel, using,data collected by the CDF II detector from <italic> pp&macr;</italic> collisions with s = 1.96 TeV at the Fermilab Tevatron. The likelihood in top mass is calculated for each event by convoluting the leading order matrix element describing <italic>qq&macr;</italic> &rarr; <italic>tt&macr;</italic> &rarr; <italic> b</italic>&ell;nu_&ell;<italic>b&macr;</italic>&ell;'nu_&ell;' with detector resolution functions. The presence of background events in the data sample is modeled using similar calculations involving the matrix elements for major background processes. In a data sample with integrated luminosity of 1.0 fb<super>-1</super>, we observe 78 candidate events and measure <italic>M_t</italic> = 164.5 +/- 3.9(stat.) +/- 3.9(syst.) GeV/<italic>c</italic><super>2</super>, the most precise measurement of the top quark mass in this channel to date.