Measurement of the Top Quark Mass Using Dilepton Events

Abstract

The D0 collaboration has performed a measurement of the top quark mass based on six candidate events for the process t tbar -> b W+ bbar W-, where the W bosons decay to e nu or mu nu. This sample was collected during an exposure of the D0 detector to an integrated luminosity of 125 pb^-1 of sqrt(s)=1.8 TeV p-pbar collisions. We obtain mt = 168.4 +- 12.3 (stat) +- 3.7 (sys) GeV/c^2, consistent with the measurement obtained using single-lepton events. Combination of the single-lepton and dilepton results yields mt = 172.0 +- 7.5 GeV/c^2.

Figures (3)

• Figure 1: $W(m_t)$ distributions for the six dilepton candidates, using the ${\cal M}$WT (dashed) and $\nu$WT (solid) methods.
• Figure 2: Sum of the normalized candidate weights grouped into the five bins considered in the maximum likelihood fit (circles) for the (a) ${\cal M}$WT and (b) ${\nu}$WT analyses. The uncertainty on these points is taken from the RMS spread of the weights in MC studies. Also shown are the average weights from the best-fit background (dashed) and signal plus background (solid). The $-\ln L$ distributions and quadratic fits are inset.
• Figure 3: Distribution of $\widehat{m}_t$ for "experiments" with $m_t^{MC}=170$ GeV/ c$^2$ (marked by vertical line) using the ${\cal M}$WT (dashed) and $\nu$WT (solid) analysis methods.