Measurement of the $W$ Boson Mass

We present a measurement of the $W$ boson mass in $W\to e\nu$ decays using $1{\mathrm{fb}}^{-1}$ of data collected with the D0 detector during Run II of the Fermilab Tevatron collider. With a sample of 499830 $W\to e\nu$ candidate events, we measure $M_W=80.401\pm 0.043\mathrm{GeV}$. This is the most precise measurement from a single experiment.

Figure 1

(a) The dielectron invariant mass distribution in $Z\to ee$ data and from the fast simulation FASTMC and (b) the $\chi$ values where ${\chi }_i=[N_i-({\mathrm{FASTMC}}_i)]/{\sigma }_i$ for each point in the distribution, $N_i$ is the data yield in bin $i$, 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 point in the distribution, $N_i$ is the data yield in bin $i$, and only the statistical uncertainty is used. The fit ranges are indicated by the double-ended horizontal arrows.