Measurement of the $W$ Boson Mass with the D0 Detector

We present a measurement of the $W$ boson mass using data corresponding to $4.3{\mathrm{fb}}^{-1}$ of integrated luminosity collected with the D0 detector during Run II at the Fermilab Tevatron $p\overline{p}$ collider. With a sample of 1 677 394 $W\to e\nu$ candidate events, we measure $M_W=80.367\pm 0.026\mathrm{GeV}$. This result is combined with an earlier D0 result determined using an independent Run II data sample, corresponding to $1{\mathrm{fb}}^{-1}$ of integrated luminosity, to yield $M_W=80.375\pm 0.023\mathrm{GeV}$.

Figure 1

(a) The dielectron invariant mass distribution in $Z\to ee$ data and from the fastmc and (b) the $\chi$ values, where ${\chi }_i=[N_i-({\mathrm{FASTMC}}_i)]/{\sigma }_i$ for each bin in the distribution, $N_i$ and ${\mathrm{FASTMC}}_i$ are the data and fastmc template yields in bin $i$, respectively, and ${\sigma }_i$ is the statistical uncertainty in bin $i$.

Figure 2

The (a) $m_T$, (b) $p_T^e$, and (c) ${\mathrm{E̸}}_T$ distributions for data and fastmc simulation with backgrounds. The $\chi$ values are shown below each distribution, where ${\chi }_i=[N_i-({\mathrm{FASTMC}}_i)]/{\sigma }_i$ for each bin in the distribution, $N_i$ and ${\mathrm{FASTMC}}_i$ are the data and fastmc template yields in bin $i$, respectively, and ${\sigma }_i$ is the statistical uncertainty in bin $i$. The fit ranges are indicated by the double-ended horizontal arrows.

Figure 3

Contour curves of 68% probability in the ($M_t$, $M_W$) plane. The ellipse represents the measurement of $M_t$ from Ref. [11] and the measurement of $M_W=80.375\pm 0.023\mathrm{GeV}$ reported in this Letter. The bands show the SM prediction for different Higgs boson mass hypotheses that are not yet ruled out by direct searches [30] for the Higgs boson.