Revisiting no-scale supergravity inspired scenarios: Updated theoretical and phenomenological constraints
Résumé
We consider no-scale inspired supergravity scenarios, where the gravitinomass and related soft supersymmetry-breaking parameters are determineddynamically by radiative corrections to an essentially flat tree-levelpotential in the supersymmetry breaking hidden sector. We examine thetheoretical and phenomenological viability of such a mechanism, when includingup-to-date calculations of the low energy sparticle spectrum and taking intoaccount the latest LHC results and other experimental constraints. We(re)emphasize the role of the scale-dependent vacuum energy contribution to theeffective potential, in obtaining realistic no-scale electroweak minima,examining carefully the impact of boundary conditions and of variants of theminimization procedure. We also discuss and implement the B_0 (soft breakingHiggs mixing parameter) input boundary condition at high scale, thereforefixing tan beta(B_0) at low scales. For general high scale boundary conditionswith non-vanishing B_0, m_0..., our analysis provides theoretical correlationsamong the supersymmetric, soft and vacuum energy parameters and relatedphenomenological consequences at the LHC. For instance, a zero vacuum energy atthe GUT scale would lead to a decoupled supersymmetric spectrum, together witha light standard model-like Higgs boson at the electroweak scale. Given theexperimental exclusion limits, a substantial class of the boundary conditions,and in particular the strict no-scale with m_0=A_0=B_0=0, are only compatiblewith a stau being the lightest MSSM particle. Then an enlarged allowedparameter space emerges when assuming a gravitino LSP to account for theobserved dark matter relic density.
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