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.
Highlights
The mass of the top quark is an important parameter of the Standard Model (SM) of particle physics
Signal Monte Carlo generator: The difference in mtop between the event sample produced with the MC@nextto-leading order (NLO) program [62,63] and the default Powheg sample, both generated at mtop = 172.5 GeV and using the Herwig program for parton shower, hadronisation and underlying event, is quoted as a systematic uncertainty
The top quark mass is from about 20.2 fb−1 me√asured of s = 8 in the tt → dilepton chanTeV proton–proton collision data recorded by the ATLAS detector at the LHC
Summary
The mass of the top quark (mtop) is an important parameter of the Standard Model (SM) of particle physics. Combining a selection of those, the first Tevatron+LHC mtop result is mtop = 173.34 ± 0.27 (stat) ± 0.71 (syst) GeV, with a total uncertainty of 0.76 GeV [7]. The latest ATLAS results in the tt → lepton + jets and tt → dilepton decay channels, both with electrons (e) and muons (μ) in the final state [14], are mtop = 172.33 ± 0.75 (stat) ± 1.02 (syst) GeV and mtop = 173.79 ± 0.54 (stat) ± 1.30 (syst) GeV, respectively. This Letter presents a new measurement of mtop obtained in the tt → dilepton decay channel using 201√2 data taken at a proton– proton (pp) centre-of-mass energy of s = 8 TeV, with an integrated luminosity of about 20.2 fb−1. The top quark mass measured in this way corresponds to the mass definition used in the MC program
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