ONE-LOOP EFFECTS IN SUPERGRAVITY MODELS WITH AN ADDITIONAL U(1)

For an Abelian extended supergravity model, we investigate some import ant low-energy parameters: tan beta, the Z-Z' mixing angle, lightest C P-even Higgs mass bound, Z' mass, and effective mu parameter. By integ rating the renormalization group equations from the string scale down to the weak scale we constuct the scalar potential and analyze the qua ntities above at the tree- and one-loop levels by including the contri butions of top squarks and top quark in the effective potential.