Improved tau polarisation measurement

• Main Authors: BUSKULIC, D., THULASIDAS, M.
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 1995
• Subjects: Computer Sciences; Databases and Information Systems
• Online Access: https://ink.library.smu.edu.sg/sis_research/5835; https://ink.library.smu.edu.sg/context/sis_research/article/6838/viewcontent/ppe_95_023.pdf
• Institution: Singapore Management University

Using 22 pb−1 of data collected at LEP in 1992 on the peak of the Z resonance, the ALEPH collaboration has measured the polarisation of the tau leptons decaying intoevv¯,μvv¯evv¯,μvv¯,πν, ρν and a1 ν from their individual decay product distributions. The measurement of the tau polarisation as a function of the production polar angle yields the two parametersN τ andN e, where, in terms of the axial and vector couplingsg Al andg Vl,N l=2g Vl gAl/(g 2Vl+g2Al). This analysis follows to a large extent the methods devised for the 1990 and 1991 data but with improvements which bring a better understanding of the systematic uncertainties. Combining the 1992 measurements with our previously published results yieldsN τ=0.136±0.012±0.009 andN e=0.129±0.016±0.005. Assuminge−τ universality, the measurements imply an effective weak mixing angle of sin 2 θ effW=0.2332±0.0014.