An investigation of the Lorentz structure in tau decays

This paper describes a measurement of the Michel parameters, eta , rho , xi , xi delta , the average nu /sub tau / helicity, h/sub nu tau / and the anomalous tensor coupling constant, kappa /sub tau //sup W/ in tau lepton decays using the DELPHI detector. The tau /sup +/ tau /sup -/ pairs were produced at the LEP e/sup +/e/sup -/ collider at CERN between 1992 and 1995. The Michel parameters, together with a measurement of the tau polarisation, P/sub tau /, were extracted in a simultaneous fit to the two dimensional momentum spectra of leptonic and semi-leptonic tau decays. The anomalous tensor coupling constant, kappa /sub tau //sup W/ was measured using the same selected data. (16 refs).