Combination of the top-quark mass measurements from the Tevatron collider

The top quark is the heaviest known elementary particle, with a mass about 40 times larger than the mass of its isospin partner, the bottom quark. It decays almost 100% of the time to a $W$ boson and a bottom quark. Using top-antitop pairs at the Tevatron proton-antiproton collider, the CDF and D0 Collaborations have measured the top quark’s mass in different final states for integrated luminosities of up to $5.8{\mathrm{fb}}^{-1}$. This paper reports on a combination of these measurements that results in a more precise value of the mass than any individual decay channel can provide. It describes the treatment of the systematic uncertainties and their correlations. The mass value determined is $173.18\pm 0.56(\mathrm{stat})\pm 0.75(\mathrm{syst})\mathrm{GeV}$ or $173.18\pm 0.94\mathrm{GeV}$, which has a precision of $\pm 0.54\%$, making this the most precise determination of the top-quark mass.

Figure 1

Examples of tree Feynman diagrams for $t\overline{t}$ production. At the Tevatron collider, the $q\overline{q}$ channel contributes 81% to the total $t\overline{t}$ inclusive cross section and the $gg$ channel the remaining 19% [69, 96].

Figure 2

Leading-order Feynman diagram for $t\overline{t}$ decay. The dilepton modes ($ee$, $e\mu$, $\mu \mu$) have a combined branching fraction of $\approx 4\%$, the $\mathrm{\text{electron}}+\mathrm{\text{jets}}$ and $\mathrm{\text{muon}}+\mathrm{\text{jets}}$ modes combined correspond to $\approx 30\%$, and the alljets mode has a branching fraction of $\approx 46\%$. The $\tau$ modes are shared among the ${\mathrm{E̸}}_T+\mathrm{\text{jets}}$ and the other channels in the analyses.

Figure 3

(a) Constraints from LEP and Tevatron measurements of $M_W$ and $m_t$ (Tevatron only) on $M_H$ within the SM. The regions in the mass of the Higgs boson still allowed after the direct searches at LEP, Tevatron, and LHC are also shown. (b) From Ref. [18], the large countors (blue) indicate the constraints on the Higgs boson, from global fits to electroweak data without including the direct measurements of $M_W$ and $m_t$ from the Tevatron.

Figure 4

The CDF and D0 published direct measurements of the top-quark mass as a function of time.

Figure 5

The average uncertainties for CDF and D0 for each Run II measurement and for the Tevatron combination, separated according to major components. (See Table 8 in the Appendix for details on the systematic categories. In this figure, the jet and lepton modeling systematic uncertainties are grouped into the modeling background category.)

Figure 6

The 12 input measurements of $m_t$ from the Tevatron collider experiments along with the resulting combined value of $m_t^{\mathrm{comb}}$. The gray region corresponds to $\pm 0.94\mathrm{GeV}$.