Could the $\tau$ be substantially different from $e$ and $\mu$ in the   supersymmetric standard model?
  R-parity stands as an ad hoc assumption in the most popular version of the supersymmetric standard model. More than fifteen years' studies of R-parity violations have been restricted to various limiting scenarios. We illustrate how the single-VEV parametrization provides a workable framework to analyze the phenomenology of the complete theory of supersymmetry without R-parity. In our comprehensive study of various aspects of the resulting leptonic phenomenology at tree-level, we find that the physical $\tau$ lepton could actually bear substantial gaugino and higgsino components, making it very different from the $e$ and the $\mu$. 
Mike Bisset (Tsinghua U.), Otto C. W. Kong, Cosmin Macesanu, Lynne H.   Orr (Rochester U.)