A study of the tau Lepton polarization in Z0 decays

[摘要] A study is presented of tau polarization observed in the channel Z° → tau+tau- and the subsequent tau decay tau →pinutau, using the ALEPH detector at the LEP collider at CERN. The polarization is a result of parity violation in the neutral and charged weak interactions. Experimentally it can be measured from the energy spectrum of the tau decay product. The detector started collecting data in 1989 and the data were taken in a range of energy in the vicinity of the Z0 pole. Observation of a non-zero polarization confirms that parity is violated in weak interactions, extending its proven existence in neutral weak currents to tau lepton interactions in agreement with the universality of the electroweak theory. Tau polarization is directly related to the ratio of the vector and axial vector couplings of the tau lepton to Z0 and hence to the effective electroweak angle Using the partial width of the Z0 decays to the tau lepton measured by this experiment, the tau couplings to the Z0 were found to be atau = -0.4969+/-0.0173 and vr = -0.035+/-0.0119.

[发布机构] University:University of Glasgow;Department:School of Physics and Astronomy

[关键词] High energy physics.