Resurrecting no-scale supergravity phenomenology

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, M _GUT, 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 renormalisation-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?β 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→s γ, the neutralino cold dark matter density Ω _χ h ² and g _μ ?2. No-scale supergravity survives in an L-shaped strip of parameter space, with one side having m _1/2?200 GeV, the second (orthogonal) side having M _in?5×10¹⁶ 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?β, 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.