Measurement of the Mass and Width of the W Boson in e+ e- Collisions at s**(1/2) = 161-GeV - 209-GeV

Abstract

A measurement of the W boson mass and width has been performed by the DELPHI collaboration using the data collected during the full LEP2 programme (1996–2000). The data sample has an integrated luminosity of 660 pb-1 and was collected over a range of centre-of-mass energies from 161 to 209 GeV. Results are obtained by applying the method of direct reconstruction of the mass of the W from its decay products in both the W+W-→ℓν̄ℓqq̄’ and W+W-→qq̄’q̄q’ channels. The W mass result for the combined data set is MW=80.336±0.055(Stat.)±0.028(Syst.)±0.025(FSI)±0.009(LEP)GeV/c2, where FSI represents the uncertainty due to final state interaction effects in the qq̄’q̄q’ channel, and LEP represents that arising from the knowledge of the collision energy of the accelerator. The combined value for the W width is ΓW=2.404±0.140(Stat.)±0.077(Syst.)±0.065(FSI)GeV/c2.These results supersede all values previously published by the DELPHI collaboration.