Simplest, string-derivable, supergravity model and its experimental predictions

We present the simplest, string-derivable, supergravity model and discuss its experimental consequences. This model is a new string-inspired flipped SU(5) which unifies at the string scale MU=1018 GeV due to the introduction of an additional pair of 10,1 bar 0 flipped SU(5) representations which contain new intermediate scale ''gap'' particles. We study various model-building issues which should be addressed in string-derived incarnations of this model. We focus our study on the no-scale supergravity mechanism and explore thoroughly the three-dimensional parameter space of the model (mg,mt,tanβ), thus obtaining several simple relationships among the particle masses, such as mq∼mg, meL∼mnu∼0.30mg, meR∼0.18mg, and mχ20∼2mχ10∼mχ1±. In a strict interpretation of the no-scale supergravity scenario we solve for tanβ as a function of mt and mg, and show that mt determines not only the sign of the Higgs mixing parameter μ but also whether the lightest Higgs boson mass is above or below 100 GeV. We also find that throughout the parameter space the neutralino relic abundance is within observational bounds (Ωχh02 approx-lt 0.25) and may account for a significant portion of the dark matter in the Universe