Combination of CDF and D0 Results on the Mass of the Top Quark
Tevatron Electroweak Working Group
TL;DR
This work combines published Run-I top-quark mass measurements with preliminary Run-II results from CDF and DØ, carefully treating correlated uncertainties across nine inputs to produce a preliminary world-average Mt = 172.5 GeV/c^2 with total uncertainty of 2.3 GeV/c^2. The analysis introduces a detailed JES-related error taxonomy and uses both numerical χ^2 minimization and the BLUE method to propagate correlations, yielding good inter-channel consistency (χ^2 ~ 8.1 for 8 dof). Run-II lepton+jets measurements dominate the precision, aided by in-situ JES calibration from W decays; the study also demonstrates the impact of correlations on input weights, including occasional negative weights. The results indicate a high-precision top-quark mass determination that is expected to improve with more Run-II data and continued refinement of JES, b-jet modeling, and Monte Carlo calibrations.
Abstract
We summarize the top-quark mass measurements from the CDF and D0 experiments at Fermilab. We combine published Run-I (1992- 1996) measurements with the most recent preliminary Run-II (2001- present) measurements using up to 750/pb of data. Taking correlated uncertainties properly into account the resulting preliminary world average mass of the top quark is Mt=172.5 +/- 1.3(stat) +/- 1.9(syst) GeV/c2, which corresponds to a total uncertainty of 2.3 GeV/c2. The top-quark mass is now known with a precision of 1.3% - a 20% improvement relative to the previous combination.