A top quark mass measurement using a matrix element method

Thesis

A measurement of the mass of the top quark is presented, using top-antitop pair (t-tbar) candidate events for the lepton+jets decay channel. The measurement makes use of Tevatron proton-antiproton collision data at centre-of-mass energy 1.96 TeV, collected at the CDF detector. The top quark mass is measured by employing an unbinned maximum likelihood method where the event probability density functions are calculated using signal (t-tbar) and background (W+jets) matrix elements, as well as a set of parameterised jet-to-parton mapping functions. The likelihood function is maximised with respect to the top quark mass, the fraction of signal events, and a correction to the jet energy scale (JES) of the calorimeter jets. The simultaneous measurement of the JES correction (ΔJES) provides an in situ jet energy calibration based on the known mass of the hadronically decaying W boson. Using 578 lepton+jets candidate events corresponding to 3.2 inverse femtobarns of integrated luminosity, the top quark mass is measured to be 172.4 ± 1.4(stat+ΔJES) ± 1.3(syst) GeV/c², one of the most precise single measurements to date.

Authors: Linacre, J; Jacob Thomas Linacre

• Publication date: 2010
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: top; quark; transfer function; Higgs; matrix element; top quark; JES; Tevatron; CDF; W+jets; likelihood; lepton+jets; jet energy scale; mass
• Subjects: Particle physics