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Measurement of the $W$ mass and width in $e^+ e^-$ collisions at 189-GeV

Research output: Contribution to journalJournal article


Journal publication date10/2000
JournalEuropean Physical Journal C: Particles and Fields
Number of pages21
Original languageEnglish


The mass of the W boson is determined in e + e − collisions at LEP by the direct reconstruction of W decays in WW→qq¯qq¯ and WW→ℓνqq¯ events, supplemented by measurements using the kinematic properties of the leptons in the \mathrm{W}\mathrm{W}\rightarrow\mbox{\ell\nu }\mbox{$\ell\nu $} 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
where FSI represents the possible effects of final state interactions in the qq¯qq¯ channel. In a second two-parameter fit to the qq¯qq¯ , \mathrmeνqq¯ and μνqq¯ 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