Resurrecting No-Scale Supergravity Phenomenology

Abstract: In the context of phenomenological models in which the soft supersymmetry-breaking parameters of the MSSM become universal at some unification scale, M_{in}, above the GUT scale, \mgut, it is possible that all the scalar mass parameters m_0, the trilinear couplings A_0 and the bilinear Higgs coupling B_0 vanish simultaneously, as in no-scale supergravity. Using these no-scale inputs in a renormalization-group analysis of the minimal supersymmetric SU(5) GUT model, we pay careful attention to the matching of parameters at the GUT scale. We delineate the region of M_{in}, m_{1/2} and \tan \beta where the resurrection of no-scale supergravity is possible, taking due account of the relevant phenomenological constraints such as electroweak symmetry breaking, m_h, b \to s \gamma, the neutralino cold dark matter density \ohsq and g_\mu - 2. No-scale supergravity survives in an L-shaped strip of parameter space, with one side having with one side having m_{1/2} \gappeq 200 {\rm GeV}, the second (orthogonal) side having M_{in} \gappeq 5 \times 10^{16} GeV. Depending on the relative signs and magnitudes of the GUT superpotential couplings, these may be connected to form a triangle whose third side is a hypotenuse at larger M_{in}, m_{1/2} and \tan \beta, whose presence and location depend on the GUT superpotential parameters. We compare the prospects for detecting sparticles at the LHC in no-scale supergravity with those in the CMSSM and the NUHM.