Measurement of the top quark mass in the $t\bar{t}\to$ dilepton channel from $\sqrt{s}=8$ TeV ATLAS data

TL;DR

This paper reports a precise measurement of the top quark mass using ATLAS data at 8 TeV in the dilepton channel, employing the template method and combining with previous results for improved accuracy.

Contribution

The study introduces a measurement of the top quark mass using the invariant mass distribution of lepton–b-jet pairs in the dilepton channel at 8 TeV, and combines it with earlier measurements for enhanced precision.

Findings

Measured top quark mass as 172.99 ± 0.84 GeV at 8 TeV.

Combined top quark mass from multiple channels as 172.84 ± 0.70 GeV.

Achieved improved total uncertainty through data combination.

Abstract

The top quark mass is measured in the $t\bar{t}\to$ dilepton channel (lepton $= e, \mu$) using ATLAS data recorded in the year 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 about 20.2 fb$^{-1}$. Exploiting the template method, and using the distribution of invariant masses of lepton--b-jet pairs, the top quark mass is measured to be $m_{top} =$ 172.99 $\pm$ 0.41 (stat) $\pm$ 0.74 (syst) GeV, with a total uncertainty of 0.84 GeV. Finally, a combination with previous ATLAS $m_{top}$ measurements from $\sqrt{s}=$7 TeV data in the $t\bar{t}\to$ dilepton and $t\bar{t}\to$ lepton+jets channels results in $m_{top} =$ 172.84 $\pm$ 0.34 (stat) $\pm$ 0.61 (syst) GeV, with a total uncertainty of 0.70 GeV.