We have searched for direct production of scalar top quarks at the Collider Detector at Fermilab in 88 pb{sup -1} of pp collisions at {radical}(s)=1.8 TeV . We assume the scalar top quark decays into either a bottom quark and a chargino or a bottom quark, a lepton, and a scalar neutrino. The event signature for both decay scenarios is a lepton, missing transverse energy, and at least two b -quark jets. For a chargino mass of 90 GeV/c{sup 2} and scalar neutrino masses of at least 40 GeV/c{sup 2} , we find no evidence for scalar top production and present upper limits on the production cross section in both decay scenarios. (c) 2000 The American Physical Society.
