In a study of the reaction e−e+→W−W+ with the DELPHI detector, the probabilities of the two W particles occurring in the joint polarisation states transverse–transverse (T T ), longitudinal–ransverse plus transverse–longitudinal (LT ) and longitudinal–longitudinal (LL) have been determined using the final states WW→lνq¯q (l =e,μ). The two-particle joint polarisation probabilities, i.e. the spin density matrix elements ρT T , ρLT , ρLL, are measured as functions of the W− production angle, θW−, at an average reaction energy of 198.2 GeV. Averaged over all cos θW−, the following joint probabilities are obtained: ρ_TT = (67±8)%, ρ_LT = (30± 8)%, ρ_LL = (3 ±7)%. These results are in agreement with the StandardModel predictions of 63.0%, 28.9% and 8.1%, respectively. The related polarisation cross-sections σTT , σLT and σLL are also presented.
|Titolo:||Correlations between polarisation states of W particles in the reaction e − e +→W − W + at LEP2 energies 189–209 GeV|
|Parole Chiave:||DELPHI ; LEP ; W boson ; polarisation|
|Settore Scientifico Disciplinare:||Settore FIS/04 - Fisica Nucleare e Subnucleare|
|Data di pubblicazione:||2009|
|Digital Object Identifier (DOI):||10.1140/epjc/s10052-009-1123-y|
|Appare nelle tipologie:||01 - Articolo su periodico|