Search for the Processe−+e−→μ−+μ−

Speculating on the possible existence of a strong muon-electron coupling which has escaped observation because of a multiplicative muon conservation law, we have looked for the process $e^{-}+e^{-}\to {\mu }^{-}+{\mu }^{-}$. We set an upper limit on the cross section of 0.67 × ${10}^{-32\mathrm{}}$ ${\mathrm{cm}}^2$ and conclude that such a coupling, if it exists, is no stronger than 610 times the normal vector coupling of weak interactions.