W boson polarisation at LEP2
G Abbiendi, C Ainsley, PF Akesson, G Alexander, J Allison, P Amaral, G Anagnostou, KJ Anderson, S Arcelli, S Asai, D Axen, G Azuelos, I Bailey, E Barberio, T Barillari, RJ Barlow, RJ Batley, P Bechtle, T Behnke, KW Bell Show all
PHYSICS LETTERS B | ELSEVIER | Published : 2004
Elements of the spin density matrix for W bosons in e+e -→W+W -→qq̄′ℓνℓ events are measured from data recorded by the OPAL detector at LEP. This information is used to calculate polarised differential cross-sections and to search for CP-violating effects. Results are presented for W bosons produced in e+e - Collisions with centre-of-mass energies between 183 GeV and 209 GeV. The average fraction of W bosons that are longitudinally polarised is found to be (23.9±2.1±1.1)% compared to a Standard Model prediction of (23.9±0.1)%. All results are consistent with CP conservation. © 2004 Elsevier B.V. All rights reserved.