We have searched for new sequential heavy leptons $L^{\pm }$ in $e^{+}$$e^{\mathrm{-}}$ collisions at √s =52 GeV using the TOPAZ detector at the KEK storage ring TRISTAN. In the collected data with an integrated luminosity of 3.6 ${\mathrm{pb}}^{\mathrm{-}1}$, no evidence for $L^{\pm }$ production has been observed. A lower mass limit for $L^{\pm }$ is determined to be 25.5 GeV/$c^2$ at 95% confidence level.

• Received 18 November 1987

DOI:https://doi.org/10.1103/PhysRevD.37.1339