Search for a fourth-generation quark with‖Q‖=e/3ine+e−collisions at√s =56–57 GeV

Abstract
A search for a fourth-generation quark with ‖Q‖=e/3 has been made with the VENUS detector at the KEK e+ e 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 collision at √s =56–57 GeV and a lower limit on the mass is 27.5 GeV/c2 at the 95% C.L.