A search for a fourth-generation quark with ‖Q‖=e/3 has been made with the VENUS detector at the KEK $e^{+}$$e^{\mathrm{-}}$ collider TRISTAN. Multihadron events with a spherical shape or containing isolated leptons were studied. There is no evidence for an excess production of such events in $e^{+}$$e^{\mathrm{-}}$ collision at √s =56–57 GeV and a lower limit on the mass is 27.5 GeV/$c^2$ at the 95% C.L.

• Received 23 December 1988

DOI:https://doi.org/10.1103/PhysRevD.39.3524