A string no-scale supergravity model and its experimental consequences

Abstract

We propose a string-derived model based on the gauge group $SU(5)\times U(1)$ which satisfies the stringent constraints from no-scale supergravity, allows gauge coupling unification at the string scale, and entails previously unexplored correlations among various sectors of the model. All supersymmetric observables are given in terms of a single mass parameter with self-consistency of the model determining the rest, including $\tanβ=2.2-2.3$ and $m_t\approx175\GeV$. A small non-universality of the scalar masses at the string scale produces a downward shift in the right-handed slepton masses at the electroweak scale, such that for $m_{1/2}\gsim180\GeV$ these particles become lighter than the lightest neutralino. This cutoff in the parameter space entails the imminent discovery of charginos at the Tevatron via trilepton events ($m_{χ^\pm_1}<90\GeV$). Also, the lightest Higgs boson ($m_h<90\GeV$), the lightest chargino, and the right-handed sleptons ($m_{\tilde\ell_R}<50\GeV$) should be readily observable at LEPII. We also discuss the model predictions for $B(b\to sγ)$, $(g-2)_μ$, $R_b$, and the prospects for direct neutralino dark matter detection.