Optimising Stop Naturalness

Chris Wymant

doi:10.1103/PhysRevD.86.115023

paper

Optimising Stop Naturalness

arXiv:1208.1737 · doi:10.1103/PhysRevD.86.115023

Abstract

In supersymmetric models a large average stop mass $M_{S}$ is well known to both boost the lightest Higgs boson mass $m_{h}$ and also make radiative electroweak symmetry breaking unnaturally tuned. The case of `maximal mixing', where the stop trilinear mixing term $A_{t}$ is set to give $A_{t}^{2} / M_{S}^{2} = 6$ , allows the stops to be as light as possible for a given $m_{h}$ . Here we make the distinction between minimal $M_{S}$ and optimal naturalness, showing that the latter occurs for less-than-maximal mixing. Lagrange constrained optimisation reveals that the two coincide closely in the Minimal Supersymmetric Standard Model (MSSM) -- optimally we have $5 < A_{t}^{2} / M_{S}^{2} < 6$ . We discuss why the two are not generally expected to coincide beyond the MSSM, and that even within the MSSM different models should not be compared based on the $M_{S}$ necessary to achieve a given $m_{h}$ . The splitting between the two stop-mass eigenvalues $m_{t ~_{2}} - m_{t ~_{1}}$ is shown to be unconstrained by naturalness considerations.

14 pages, 3 figures. v2 and 3: extra content. v4: typos, PRD version

Optimising Stop Naturalness

Abstract

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