1997/01/31 by SLD Collaboration, K. Abe, K. Abe etal +98
Physics and Astronomy · #Astrophysics and Cosmic Phenomena #Neutrino Physics Research #Particle physics theoretical and experimental studies #hep-ex
paper · pdf · doi:10.1103/physrevlett.78.4691
published as Phys.Rev.Lett.78:4691-4696,1997 · 10 pages, LaTex document, 2 figures all in gzip tar file. Also available in gzip-compressed postscript form (64 Kb) at http://www.slac.stanford.edu/~erez/hnutex/lorentz.ps.gz Uncompressed postscript file (214 Kb) available to DECNET users as SLACVX: :DISK$SLD_USR0:[EREZ.XXX]LORENTZ.PS to be published at Phys. Rev. Lett. 78 (June 1997)
arxiv created 1997/05/07 · openalex publication_date 1997/06/23 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/28
We present a new measurement of the \ensuremathτ neutrino helicity h_\ensuremathν_\ensuremathτ and the \ensuremathτ Michel parameters \ensuremathρ, \ensuremathη, \ensuremathξ, and the product \ensuremathδ\ensuremathξ. The analysis exploits the highly polarized SLC electron beam to extract these quantities directly from a measurement of the \ensuremathτ decay spectra, using the 1993--1995 SLD data sample of 4328 e+e^\ensuremath-\ensuremath→Z0\ensuremath→\ensuremathτ+\ensuremathτ^\ensuremath- events. From the decays \ensuremathτ\ensuremath→\ensuremathπ\ensuremathν_\ensuremathτ and \ensuremathτ\ensuremath→\ensuremathρ\ensuremathν_\ensuremathτ we obtain a combined value h_\ensuremathν_\ensuremathτ\phantom\rule0ex0ex=\phantom\rule0ex0ex\ensuremath-0.93\ifmmode±\else\textpm\fi0.10\ifmmode±\else\textpm\fi0.04. The leptonic decay channels yield combined values of \ensuremathρ\phantom\rule0ex0ex=\phantom\rule0ex0ex0.72\ifmmode±\else\textpm\fi0.09\ifmmode±\else\textpm\fi0.03, \ensuremathξ\phantom\rule0ex0ex=\phantom\rule0ex0ex1.05\ifmmode±\else\textpm\fi0.35\ifmmode±\else\textpm\fi0.04, and \ensuremathδ\ensuremathξ\phantom\rule0ex0ex=\phantom\rule0ex0ex0.88\ifmmode±\else\textpm\fi0.27\ifmmode±\else\textpm\fi0.04.