Given a lepton number $L=1\mathrm{}$ for $e$, ${\nu }_e$, $\mu$, and ${\nu }_{\mu }$, all available data at present are compatible with $L=0\mathrm{}$ for $\tau$ and ${\nu }_{\tau }$. A model with such an assignment is shown to be as natural as the conventional one in a supersymmetric extension of the standard model. Processes such as $p\overline{p}(orpp)\to {\tau }^{\pm }{\tau }^{\pm }+$ two quark jets as well as $\mathrm{ep}\to {\tau }^{-}{\tau }^{-}+$ one quark jet+missing energy ($p_T$) provide unique signatures of this possibility.

• Received 21 July 1989

DOI:https://doi.org/10.1103/PhysRevD.41.988