Study of Spin and DecayPlane Correlations of W Bosons in the e+e W+W Process at LEP.pdfVIP

EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCH CERN-EP/2003-072 November 12, 2003 Study of Spin and Decay-Plane Correlations + − + − of W Bosons in the e e → W W Process at LEP 5 0 0 2 n a J 4 1 The L3 Collaboration 1 v 6 3 0 1 0 5 0 / Abstract x e p- Data collected at LEP at centre-of-mass energies √s = 189 − 209 GeV are used e to study correlations of the spin of W bosons using e+e− → W+W− → ℓνq¯q events. h : Spin correlations are favoured by data, and found to agree with the Standard Model v predictions. In addition, correlations between the W-boson decay planes are studied i X in e+e− → W+W− → ℓνq¯q and e+e− → W+W− → q¯qq¯q events. Decay-plane r correlations are measured to be consistent with the Standard Model predictions. a Submitted to Eur. Phys. Jour. C Introduction The study of the properties of the W boson constitutes one of the main physics goals of the LEP experiments. We have previously reported on the measurement of the helicity fractions of W bosons in e+e− → W+W− → ℓνq¯q events, with ℓ denoting either an electron or a muon, using data collected at LEP at centre-of-mass energies, √s, up to 209 GeV [1]. Measurements of W-boson polarisation were also reported in the framework of a spin-density matrix analysis [2]. The same data sample is used here to study correlations of the spin of W bosons as well as correlations between the decay planes of the two W bosons. This last study also includes e+e− → W+W− → q¯