Low-energy supersymmetry with D-term contributions to scalar masses

We investigate how the predictions of the minimal supersymmetric standard model are modified by D-term contributions to soft scalar masses, which arise whenever the rank of the gauge group at very high energies is greater than four. We give a parametrization of the most general such contributions that can occur when the unbroken gauge symmetry is an arbitrary subgroup of E(6), and show how the D-term contributions leave their imprint on physics at ordinary energies. We impose experimental constraints on the resulting parameter space and discuss some features of the resulting supersymmetric spectrum which differ from the predictions obtained with universal boundary conditions on scalar masses near the Planck scale. These include relations between squark and slepton masses, the behavior of sin(2)(beta-alpha) (which determines the production cross section for the lightest Higgs scalar boson at an e(+)e(-) collider) and the mass of the pseudoscalar Higgs bosons, R(b) [the ratio Gamma(Z --> b (b) over bar)/Gamma(Z --> hadrons)], and mass differences between charginos and neutralinos.