The ratios of the numbers of Z bosons decaying to e+e−, μ+μ− and τ+τ− pairs to the number decaying to hadrons have been measured. The branching ratios and partial widths for each channel were determined and found to be equal, consistent with lepton universality. The mean leptonic branching ratio was found to be 0.0321 ± 0.0013 and the leptonic partial width to be 85.4 ± 5.3 MeV. The partial widths for hadronic decays and for invisible decays were deduced to be 1833 ± 116 MeV and 569 ± 92 MeV, respectively. The number of light neutrino types, assuming only the standard model value for the ratio theta_3/theta_nu, was found to be 3.35 ± 0.41.
|Titolo:||Determination of the leptonic branching ratios of the Z|
|Settore Scientifico Disciplinare:||Settore FIS/01 - Fisica Sperimentale|
|Data di pubblicazione:||1990|
|Digital Object Identifier (DOI):||10.1016/0370-2693(90)91949-C|
|Appare nelle tipologie:||01 - Articolo su periodico|