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 m₀, the trilinear couplings A₀ and the bilinear Higgs coupling B₀ 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→sγ, the neutralino cold dark matter density Ω_χh² 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.