Measurement of the mass and the width of the W boson at LEP

The mass and the total decay width of the W boson are measured with the L3 detector at the LEP e(+)e(-) collider using W-boson pairs produced in 0.7 fb(-1) of data collected at centre-of-mass energies between 161 and 209 GeV. Combining semi-leptonic and fully-hadronic final states, the mass and the width of the W boson are determined to be m(W) = 80.270 +/- 0.046 +/- 0.031 GeV and Gamma(W) = 2.18 +/- 0.11 +/- 0.09 GeV , where the first uncertainty is statistical and the second systematic.