Constraining new interactions with leptonic τ decays

Abstract
The recent measurements of the Michel parameters in τ decays enable, for the first time, a thorough analysis of the leptonic sector. In general, in models beyond the standard model, these parameters will be altered through changes in the W and Z couplings, and/or through interactions mediated by new gauge bosons. We perform a complete, model-independent analysis of the constraints imposed by the present data on such boson-mediated interactions, and point out the existence of useful relations among the couplings.
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