A. Brignole et F. Zwirner, SUPERSYMMETRY AND SU(2)XU(1) BREAKING WITH NATURALLY VANISHING VACUUMENERGY, Physics letters. Section B, 342(1-4), 1995, pp. 117-124
We show how the spontaneous breaking of local N = 1 supersymmetry and
of the SU(2) x U(1) gauge symmetry can be simultaneously realized, wit
h naturally vanishing tree-level vacuum energy, in superstring effecti
ve supergravities. Both the gravitino mass m(3/2) and the electroweak
scale mt are classically undetermined, and slide along moduli directio
ns that include the Higgs flat direction \H-1(0)\ = \H-2(0)\ There are
important differences with conventional supergravity models: the gold
stino has components along the higgsino direction; SU(2) x U(1) breaki
ng occurs already at the classical level; the scales m(3/2) and M(z),
the gauge couplings, the lightest Higgs mass and the cosmological cons
tant are entirely determined by quantum corrections.