ASPECTS OF RADIATIVE ELECTROWEAK BREAKING IN SUPERGRAVITY MODELS

We discuss several aspects of state-of-the-art calculations of radiative electroweak symmetry breaking in supergravity models. These models have a five-dimensional parameter space in contrast with the 21-dimensional one of the MSSM. We examine the Higgs one-loop effective potential V1 = V0 + DELTAV, in particular how its renormalization-scale (Q) independence is affected by the approximation used to calculate DELTAV and by the presence of a Higgs-field-independent term which makes V1(0) not-equal 0. We show that the latter must be subtracted out to achieve Q-independence. We also discuss our own approach to the exploration of the five-dimensional parameter space and the fine-tuning constraints within this approach. We apply our methods to the determination of the allowed region in parameter space of two models which we argue to be the prototypes for conventional (SSM) and string (SISM) unified models. To this end we impose the electroweak breaking constraint by minimizing the one-loop effective potential and study the shifts in mu and B relative to the values obtained using the tree-level potential. These shifts are most significant for small values of mu and B, and induce corresponding shifts on the lightest mu-and/or B-dependent particle masses, i.e., those of the lightest stau, neutralino, chargino, and Higgs boson states. Finally, we discuss the predictions for the squark, slepton, and one-loop corrected Higgs boson masses.