Measurement of the W boson mass and width in e+e- collisions at LEP

The mass of the W boson is determined from the direct reconstruction of W decays in WW -> qqqq and WW -> lvqq events in e(+)e(-) collisions at LEP. The data sample corresponds to an integrated luminosity of 683 pb(-1) collected with the ALEPH detector at centre-of-mass energies up to 209 GeV. To minimise any effect from colour reconnection a new procedure is adopted in which low energy particles are not considered in the mass determination from the qqqq channel. The combined result from all channels is mw = 80.440 +/- 0.043(stat.) +/- 0.024(syst.) +/- 0.009(FSI) +/- 0.009 (LEP)GeV/c(2), where PSI represents the possible effects of final state interactions in the qqqq channel and LEP indicates the uncertainty in the beam energy. From two-parameter fits to the W mass and width, the W width is found to be Gamma(W) = 2.14 +/- 0.09(stat.) +/- 0.04(syst.) +/- 0.05 (FSI) +/- 0.01 (LEP)GeV.