Institut de recherche sur les lois fondamentales de l'Univers

The W boson mass is a fundamental parameter of the Standard Model. Through radiative corrections, the measured top quark and W boson masses can be used to predict the mass of the Higgs boson. This talk will present a first measurement of M_W in Run II of the Tevatron program using ~200/pb of data taken with the CDF II detector. With 63,964 W->e nu candidates and 51,128 W->mu nu candidates, we measure M_W = 80413 ± 34 (stat) ± 34 (syst) MeV. With a total uncertainty of 48 MeV, this represents the single most precise W boson mass measurement to date.