Revisiting No-Scale Supergravity Inspired Scenarios: Updated Theoretical and Phenomenological Constraints

TL;DR

This paper revisits no-scale supergravity models, updating their theoretical and phenomenological constraints with recent experimental data, and explores the implications of boundary conditions and vacuum energy contributions on the supersymmetric spectrum and Higgs mass.

Contribution

It provides a comprehensive analysis of no-scale supergravity scenarios incorporating latest LHC results, boundary condition effects, and vacuum energy contributions, highlighting their impact on the supersymmetric spectrum and dark matter candidates.

Findings

Zero vacuum energy at GUT scale implies a decoupled spectrum and light Higgs.

Strict no-scale boundary conditions favor a stau LSP.

Allowing gravitino LSP expands viable parameter space.

Abstract

We consider no-scale inspired supergravity scenarios, where the gravitino mass and related soft supersymmetry-breaking parameters are determined dynamically by radiative corrections to an essentially flat tree-level potential in the supersymmetry breaking hidden sector. We examine the theoretical and phenomenological viability of such a mechanism, when including up-to-date calculations of the low energy sparticle spectrum and taking into account the latest LHC results and other experimental constraints. We (re)emphasize the role of the scale-dependent vacuum energy contribution to the effective potential, in obtaining realistic no-scale electroweak minima, examining carefully the impact of boundary conditions and of variants of the minimization procedure. We also discuss and implement the B_0 (soft breaking Higgs mixing parameter) input boundary condition at high scale, therefore fixing tan beta(B_0) at low scales. For general high scale boundary conditions with non-vanishing B_0, m_0..., our analysis provides theoretical correlations among the supersymmetric, soft and vacuum energy parameters and related phenomenological consequences at the LHC. For instance, a zero vacuum energy at the GUT scale would lead to a decoupled supersymmetric spectrum, together with a light standard model-like Higgs boson at the electroweak scale. Given the experimental 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 compatible with a stau being the lightest MSSM particle. Then an enlarged allowed parameter space emerges when assuming a gravitino LSP to account for the observed dark matter relic density.