This paper explores the present experimental limits on the existence of a hypothetical force which would only couple to charged leptons; the neutral particle carrying the force having a mass greater than several MeV/${\mathit{c}}^2$. We consider limits from data on $g_e-2\mathrm{}$, $g_{\mu }-2\mathrm{}$, electron beam-dump experiments, $e^{+}+e^{-}\to e^{+}+e^{-}$, $e^{+}+e^{-}\to {\mu }^{+}+{\mu }^{-}$, and $e^{+}+e^{-}\to {\tau }^{+}+{\tau }^{-}$. Our purpose is to provide a basis for design of future experiments which would be more sensitive to the existence of a charged-lepton-specific force or other unknown phenomena connected to charged leptons.

• Received 17 February 1989

DOI:https://doi.org/10.1103/PhysRevD.40.823