Measurement of the top quark mass in the tt → lepton+jets and tt → dilepton channels using √s=7 TeV ATLAS data

Aad, G. and Abbott, B. and Abdallah, J. and Abdinov, O. and Aben, R. and Krasznahorkay, Attila and Nagai, Yoshikazu and Pásztor, Gabriella and Tóth, József (2015) Measurement of the top quark mass in the tt → lepton+jets and tt → dilepton channels using √s=7 TeV ATLAS data. EUROPEAN PHYSICAL JOURNAL C, 75 (7). ISSN 1434-6044

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Abstract

The top quark mass was measured in the channels t¯t → lepton+jets and t¯t → dilepton (lepton=e, μ) based on ATLAS data recorded in 2011. The data were taken at the LHC with a proton–proton centre-of-mass energy of √s = 7 TeV and correspond to an integrated lumin- osity of 4.6 fb−1. The t¯t → lepton+jets analysis uses a three-dimensional template technique which determines the top quark mass together with a global jet energy scale factor (JSF), and a relative b-to-light-jet energy scale factor (bJSF), where the terms b-jets and light-jets refer to jets originating from b-quarks and u, d, c, s-quarks or gluons, respectively. The ana- lysis of the t¯t → dilepton channel exploits a one-dimensional template method using the m`b observable, defined as the average invariant mass of the two lepton+b-jet pairs in each event. The top quark mass is measured to be 172.33 ± 0.75(stat + JSF + bJSF) ± 1.02(syst) GeV, and 173.79 ± 0.54(stat) ± 1.30(syst) GeV in the t¯t → lepton+jets and t¯t → dilepton chan- nels, respectively. The combination of the two results yields mtop = 172.99 ± 0.48(stat) ± 0.78(syst) GeV, with a total uncertainty of 0.91 GeV.

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