Direct Measurement of the Top Quark Mass at D0
D0 Collaboration, B. Abbott
TL;DR
This work addresses the precise measurement of the top-quark mass using t tbar events produced in p pbar collisions at sqrt(s)=1.8 TeV with the DØ detector. It employs lepton+jets and dilepton final states, applying jet-energy corrections and multiple kinematic fitting techniques (two- and three-constraint) to extract m_t via likelihood methods, supplemented by a fixed-mass χ^2 approach. The reported results yield m_t(l+jets) = 173.3 ± 5.6 (stat) ± 5.5 (syst) GeV/c^2 and a combined m_t = 172.1 ± 5.2 (stat) ± 4.9 (syst) GeV/c^2, with a consistent fixed-mass analysis around 176.0 GeV/c^2; overall, the analysis achieves a notable improvement in precision over prior measurements. These mass determinations contribute to electroweak fits and Higgs boson mass constraints within the Standard Model.
Abstract
We determine the top quark mass m_t using t-tbar pairs produced in the D0 detector by \sqrt{s} = 1.8 TeV p-pbar collisions in a 125 pb^-1 exposure at the Fermilab Tevatron. We make a two constraint fit to m_t in t-tbar -> b W^+bbar W^- final states with one W boson decaying to q-qbar and the other to e-nu or mu-nu. Likelihood fits to the data yield m_t(l+jets) = 173.3 +- 5.6 (stat) +- 5.5 (syst) GeV/c^2. When this result is combined with an analysis of events in which both W bosons decay into leptons, we obtain m_t = 172.1 +- 5.2 (stat) +- 4.9 (syst) GeV/c^2. An alternate analysis, using three constraint fits to fixed top quark masses, gives m_t(l+jets) = 176.0 +- 7.9 (stat) +- 4.8 (syst) GeV/C^2, consistent with the above result. Studies of kinematic distributions of the top quark candidates are also presented.