Measurement of the top-quark mass in t t-bar events with lepton+jets final states in pp collisions at sqrt(s) = 7 TeV

TL;DR

This paper reports a precise measurement of the top-quark mass using lepton+jets final states in proton-proton collisions at 7 TeV, employing a kinematic fit and jet energy scale calibration.

Contribution

It introduces a method to simultaneously measure the top-quark mass and jet energy scale in t t-bar events at the LHC.

Findings

Top-quark mass measured as 173.49 GeV

Achieved a total uncertainty of about 1 GeV

Method improves precision of top mass measurement

Abstract

The mass of the top quark is measured using a sample of t t-bar candidate events with one electron or muon and at least four jets in the final state, collected by CMS in pp collisions at sqrt(s) = 7 TeV at the LHC. A total of 5174 candidate events is selected from data corresponding to an integrated luminosity of 5.0 inverse femtobarns. For each event the mass is reconstructed from a kinematic fit of the decay products to a t t-bar hypothesis. The top-quark mass is determined simultaneously with the jet energy scale (JES), constrained by the known mass of the W boson in q anti-q decays, to be 173.49 +/- 0.43 (stat.+JES) +/- 0.98 (syst.) GeV.