OBSERVABLES IN LOW-ENERGY SUPERSTRING MODELS

We compile phenomenological constraints on the minimal low-energy effective theory which can be obtained from the superstring by Calabi-Yau compactification. Mixing with the single additional neutral gauge boson in this model reduces the mass of the conventional Z⁰, Field vacuum expectation values are constrained by the experimental upper bound on this shift. Then, requiring the sneutrino mass squared to be positive constrains the scale of supersymmetry breaking more than do lower bounds on the masses of new charged particles and of sparticles. More model-dependent constraints follow from the “naturalness” requirement that observables do not depend sensitively on input parameters. We find a preference for the second neutral gauge boson to weigh ≲320 GeV, GeV and GeV. Dynamical generation of the gauge hierarchy is possible if m_t≲70 GeV, with lower values of m_t being favoured.