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

Research output: Contribution to journalJournal article


  • ALEPH Collaboration
<mark>Journal publication date</mark>08/2006
<mark>Journal</mark>European Physical Journal C: Particles and Fields
Issue number2
Number of pages27
Pages (from-to)309-335
<mark>Original language</mark>English


The mass of the W boson is determined from the direct reconstruction of W decays in WW→qq̄qq̄ and WW→ℓνqq̄ 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 qq̄qq̄ channel. The combined result from all channels is mW=80.440±0.043(stat.)±0.024(syst.)±0.009(FSI)±0.009(LEP)GeV/c2, where FSI represents the possible effects of final state interactions in the qq̄qq̄ 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 ΓW=2.14±0.09(stat.)±0.04(syst.)±0.05(FSI)±0.01(LEP)GeV.

Bibliographic note

Jones undertook extensive studies of potential colour reconnection in the fully hadronic channels, and so constrained imortant systematic uncertainty contributions, using multiplicities and particle flows. The measurement gives one of the most precise determinations of the electroweak coupling strength. RAE_import_type : Journal article RAE_uoa_type : Physics