SEARCH FOR TOP QUARK PRODUCTION AT THE CERN PBARP COLLIDER

The upgraded UA 2 detector has collected data corresponding to a total integrated luminosity of 7.5 pb−1 from\(\bar pp\) collisions at a centre of mass energy of 630 GeV during 1988 and 1989. A search has been performed for the production and decay of the top quark (t) or a member of a hypothetical fourth family (b′). No evidence has been found for such processes. Using the expected rates for production and decay branching ratios from the Standard Model, this implies that the top quark mass is greater than 69(71) GeV/c2, and that theb′ mass is greater than 54(57) GeV/c2, at 95(90)% confidence.