Measurement of the top quark mass in the $t\bar{t}\to$ lepton+jets channel from $\sqrt{s}=8$ TeV ATLAS data and combination with previous results

Abstract

The top quark mass is measured using a template method in the $t\bar{t}\to$ lepton+jets channel (lepton is $e$ or $\mu$) using ATLAS data recorded in 2012 at the LHC. The data were taken at a proton-proton centre-of-mass energy of $\sqrt{s}=8$ TeV and correspond to an integrated luminosity of 20.2 fb$^{-1}$. The $t\bar{t}\to$ 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 $m_{top}= 172.08 \pm 0.39 (stat) \pm 0.82 (syst)$ GeV. A combination with previous ATLAS $m_{top}$ measurements gives $m_{top}= 172.69 \pm 0.25 (stat) \pm 0.41 (syst)$ GeV.