Measurement of the top quark mass in the tt¯ → lepton+jets channel from √s =8 TeV ATLAS data and combination with previous results

The top quark mass is measured using a template method in the tt¯→lepton+jets channel (lepton is e or μ) using ATLAS data recorded in 2012 at the LHC. The data were taken at a proton–proton centre-of-mass energy of √s =8 TeV and correspond to an integrated luminosity of 20.2 fb⁻¹. The tt¯→lepton+jets channel is characterized by the presence of a charged lepton, a neutrino and four jets, two of which originate from bottom quarks (b). Exploiting a three-dimensional template technique, the top quark mass is determined together with a global jet energy scale factor and a relative b-to-light-jet energy scale factor. The mass of the top quark is measured to be m_top=172.08±0.39(stat)±0.82(syst) GeV. A combination with previous ATLAS m_top measurements gives m_top=172.69±0.25(stat)±0.41(syst) GeV.