| Abstract (en) |
The mass of the W boson is determined in e+ e- collisions at LEP by the direct reconstruction of W decays in W W q q q q and W W lq q events, supplemented by measurements using the kinematic properties of the leptons in the W W ll decay channel. The main sample of W pairs is selected from an integrated luminosity of 174 pb-1 collected with the ALEPH detector in 1998 at a centre-of-mass energy of 188.63 GeV. The combined result from all channels is mW = 80.432 ± 0.072(stat.) ± 0.041(syst.) ± 0.019(F SI) ± 0.017(LEP )GeV /c2 , where FSI represents the possible effects of final state interactions in the q q channel. In a second two-parameter fit to the qq q , eq q and µq q channels, where the W mass and width are decoupled. the average W width is found to be 2.24 ± 0.20(stat.) ± 0.13(syst.) GeV /c2 , consistent with the Standard Model prediction. The combination of the mass measurement presented in this paper together with those derived previously from the W pair cross section at 161 and 172 GeV and direct reconstruction at 172 and 183 GeV gives mW = 80.418 ± 0.061(stat.) ± 0.040(syst.) ± 0.019(F SI) ± 0.017(LEP )GeV /c2 . |
