Precise measurement of the top-quark mass from lepton+jets events at D0

TL;DR

This work delivers a precise top-quark mass measurement in tt̄ events with the D0 detector by employing a matrix element technique that couples an in situ jet energy calibration to a standard JES and a flavor-dependent jet response correction. Through detailed MC calibration, transfer-function modeling, and rigorous systematic uncertainty assessment across production, detector, and method categories, the study achieves mt = 176.01 ± 1.64 GeV for the 2.6 fb^{-1} sample and, when combined with a prior 1 fb^{-1} result, mt = 174.94 ± 1.49 GeV. A dedicated flavor-dependent jet-response correction reduces data-MC mismatches in calorimeter jet energy deposition, significantly tightening the systematic budget. The combined result contributes to a robust Tevatron-era determination of mt and informs global fits constraining the Higgs sector and potential new physics.

Abstract

We report a measurement of the mass of the top quark in lepton+jets final states of ppbar->ttbar data corresponding to 2.6 fb^{-1} of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. Using a matrix element method, we combine an insitu jet energy calibration with our standard jet energy scale derived in studies of γ+jet and dijet events and employ a novel flavor-dependent jet response correction to measure a top-quark mass of mt = 176.01 +/- 1.64 GeV. Combining this result with our previous result obtained on an independent data set, we measure a top-quark mass of mt = 174.94 +/- 1.49 GeV for a total integrated luminosity of 3.6 fb^{-1}.

Figures (10)

• Figure 1: (color online) The mean acceptance as a function of $m_{t}$ and $k_{\rm JES}$ for the (a) $e$+jets and (b) $\mu$+jets channels.
• Figure 2: (color online) Transfer functions for $k_{\rm JES}$=1 light-quark jets as a function of measured jet energy for different parton energies in $\eta$ regions: (a) $|\eta|<0.5$, (b) $0.5<|\eta|<1.0$, (c) $1.0<|\eta|<1.5$, and (d) $1.5<|\eta|<2.5$.
• Figure 3: (color online) Comparison of (a) 2-jet and (b) 3-jet invariant mass distributions for parton-level $t\bar{t}$ MC events with energies smeared using the transfer functions (open histogram) and fully simulated $t\bar{t}$ MC events with all four jets spatially matched to partons (filled histogram).
• Figure 4: Mean values of (a) $m_{t}$ and (b) $k_{\rm JES}$ extracted from ensemble studies, as a function of the input values fitted to straight lines. Dashed lines represent 1:1 correlations of extracted and input values.
• Figure 5: Widths of the pull distributions for (a) $m_{t}$ and (b) $k_{\rm JES}$ from ensemble studies as a function of the input values.