Measurement of the Top Quark Mass using Dilepton Events and a Neutrino Weighting Algorithm with the DØ Experiment at the Tevatron (Run II)

Abstract

Several measurements of the top quark mass in the dilepton final states with the D0 experiment are presented. The theoretical and experimental properties of the top quark are described together with a brief introduction of the Standard Model of particle physics and the physics of hadron collisions. An overview over the experimental setup is given. The Tevatron at Fermilab is presently the highest-energy hadron collider in the world with a center-of-mass energy of 1.96 TeV. There are two main experiments called CDF and D0, A description of the components of the multipurpose D0 detector is given. The reconstruction of simulated events and data events is explained and the criteria for the identification of electrons, muons, jets, and missing transverse energy is given. The kinematics in the dilepton final state is underconstraint. Therefore, the top quark mass is extracted by the so-called Neutrino Weighting method. This method is introduced and several different approaches are described, compared, an d enhanced. Results for the international summer conferences 2006 and winter 2007 are presented. The top quark mass measurement for the combination of all three dilepton channels with a dataset of 1.05 1/fb yields: mtop=172.5+-5.5 (stat.) +- 5.8 (syst.) GeV.<br /> This result is presently the most precise top quark mass measurement of the D0 experiment in the dilepton chann el. It entered the top quark mass wold average from March 2007.