We propose a general scheme for constructing models in which the Standard
Model (SM) gauge interactions are the mediators of supersymmetry breaking to
the fields in the supersymmetric SM, but where the SM gauge groups couple
directly to the sector which breaks supersymmetry dynamically. Despite the
direct coupling, the models preserve perturbative unification of the SM gauge
coupling constants. Furthermore, the supergravity contributions to the squark
and slepton masses can be naturally small, typically being much less than 1% of
the gauge mediated contributions. Both of these goals can be achieved without
need of a fine-tuning or a very small coupling constant. This scheme requires
run-away directions at the renormalizable level which are only lifted by
non-renormalizable terms in the superpotential. To study the proposed scheme in
practice, we develop a modified class of models based on SU(N)×SU(N−1)
which allows us to gauge a SU(N−2) global symmetry. However, we point out a
new problem which can exist in models where the dynamical supersymmetry
breaking sector and the ordinary sector are directly coupled -- the two-loop
renormalization group has contributions which can induce negative (mass)2
for the squarks and sleptons. We clarify the origin of the problem and argue
that it is likely to be surmountable. We give a recipe for a successful model.Comment: 33 pages, LaTeX. Report number: LBNL-39865, UCB-PTH-96/55,
IASSNS-HEP-96/10