Direct observation of longitudinally polarised W± bosons

• Autores: Dova, María Teresa; L3 Collaboration
• Año de publicación: 2000
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Ciencias Exactas; Física; standar model; W boson; W polarisation; W decay
• Institución: Universidad Nacional de La Plata

The three different helicity states of W± bosons, produced in the reaction $\text{e}{}^{\mathrm{+}}\text{e}{}^{\mathrm{-}}\text{→}\text{W}{}^{\mathrm{+}}\text{W}{}^{\mathrm{-}}\text{→}\text{ℓνq}\text{q}\text{̄}$ are studied using leptonic and hadronic W decays at √s = 183 GeV and 189 GeV. The W polarisation is also measured as a function of the scattering angle between the W- and the direction of the e- beam. The analysis demonstrates that W bosons are produced with all three helicities, the longitudinal and the two transverse states. Combining the results from the two center-of-mass energies and with leptonic and hadronic W decays, the fraction of longitudinally polarised W± bosons is measured to be 0.261 ± 0.051 (stat.) ± 0.016 (syst.) in agreement with the expectation from the Standard Model.
Facultad de Ciencias Exactas