ENHANCED SUPERSYMMETRIC CORRECTIONS TO TOP-QUARK PRODUCTION AT THE FERMILAB TEVATRON

We calculate the one-loop supersymmetric electroweaklike and QCD-like corrections to the top-quark pair-production cross section at the Ferm ilab Tevatron, including the important effects of nondegenerate top sq uarks and left-right top squark mixing. The largest electroweaklike ef fects yield a negative shift in the cross section and are enhanced rig ht below the threshold for top-quark decay into a top squark and Higgs inolike neutralino, and can be as large as -35%. The largest QCD-like effects are positive and are enhanced for light top squark masses, and can be as large as 20%. Such shifts greatly exceed the present theore tical uncertainty in the standard model prediction, and, therefore, ma y be experimentally observable. We also explore the one-loop shifts in scenarios containing light top squarks and Higgsinolike neutralinos t hat have been recently proposed to explain various apparent experiment al anomalies.