Bailey, Ian Richard.2008-04-102008-04-1020042008-04-10http://hdl.handle.net/1828/473The spin states of W bosons in e+e- -t W+W- -t q$tvc events recorded by the OPAL detector at LEP are determined by an analysis of the angular distributions of their d e cay products. 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 percentage of longitudinally polarised W bosons measured from the data is found to be (23.9 f 2.1 + 1.1)% compared to a Standard Model prediction of (23.9 f 0.1)%. All results are consistent with CP conservation.W bosons