Abstract
The mass of the top quark is measured in a data set corresponding to 4.6 text{ fb }^{-1} of proton–proton collisions with centre-of-mass energy sqrt{s}=7 TeV collected by the ATLAS detector at the LHC. Events consistent with hadronic decays of top–antitop quark pairs with at least six jets in the final state are selected. The substantial background from multijet production is modelled with data-driven methods that utilise the number of identified b-quark jets and the transverse momentum of the sixth leading jet, which have minimal correlation. The top-quark mass is obtained from template fits to the ratio of three-jet to dijet mass. The three-jet mass is calculated from the three jets produced in a top-quark decay. Using these three jets the dijet mass is obtained from the two jets produced in the W boson decay. The top-quark mass obtained from this fit is thus less sensitive to the uncertainty in the energy measurement of the jets. A binned likelihood fit yields a top-quark mass of \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\begin{aligned} m_{t} = 175.1 \\pm 1.4\\;\ ext{(stat.) }\\pm 1.2\\;\ ext{(syst.) }\\mathrm{\\,GeV}. \\end{aligned}$$\\end{document}mt=175.1±1.4(stat.)±1.2(syst.)GeV.
Highlights
The top-quark mass can be determined from decay channels involving hadronic and leptonic decays of the intermediate W boson
This decay mode is used in this analysis to measure the top-quark mass from ttpairs produced in proton–proton collisions provided by the LHC, and observed by the ATLAS detector
Underlying event: The potential uncertainty due to the choice of a particular model to simulate underlying events is evaluated by considering events simulated using Powheg- box and Pythia based on the Perugia 2012 tune and comparing to events based on the Perugia 2012 mpiHi tune [29], which has an increased rate of jets from multiparton interactions
Summary
The top-quark mass can be determined from decay channels involving hadronic and leptonic decays of the intermediate W boson. For the recent world-average top-quark mass value [5], the highest precision [6,7,8,9,10,11,12,13,14,15] comes from measurements using the lepton plus jets final state in the decay of top–antitop pairs (tt). This channel has a substantial branching fraction and allows a relatively unambiguous assignment of jets to partons from the ttdecay. Jet energies measured by the electromagnetic and hadronic calorimeters are adjusted using correction factors, obtained from an in situ calibration [17], which depend on pseudorapidity (η) and transverse momentum ( pT)
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