First run II measurement of the W boson mass at the Fermilab Tevatron

We describe a measurement of the W boson mass m(W) using 200 pb(-1) of root s=1.96 TeV p (p) over bar collision data taken with the CDF II detector. With a sample of 63 964 W -> e nu candidates and 51 128 W -> mu nu candidates, we measure m(W) = [80.413 +/- 0.034(stat) +/- 0.034(sys) = 80.413 +/- 0.048] GeV/c(2). This is the single most precise m(W) measurement to date. When combined with other measured electroweak parameters, this result further constrains the properties of new unobserved particles coupling to W and Z bosons.