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Cosmological Fine Tuning, Supersymmetry, and the Gauge Heirarchy Problem

Piotr H. Chankowski·John Ellis·Keith A. Olive·Stefan Pokorski
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Abstract

We study the extent to which the cosmological fine-tuning problem - why the relic density of neutralino cold dark matter particles $χ$ is similar to that of baryons - is related to the fine-tuning aspect of the gauge hierarchy problem - how one arranges that M_W << M_P without unnatural choices of MSSM parameters. Working in the minimal supergravity framework with universal soft supersymmetry-breaking parameters as inputs, we find that the hierarchical fine tuning is minimized for Ω_χ h^2 \sim 0.1. Conversely, imposing Ω_χ h^2 < 1 does not require small hierarchical fine tuning, but the exceptions to this rule are rather special, with parameters chosen such that m_χ\sim M_Z/2 or M_h/2, or else m_χ \simgt m_t. In the first two cases, neutralino annihilation receives a large contribution from a direct-channel pole, whereas in the third case it is enhanced by the large top Yukawa coupling.

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Piotr H. Chankowski, John Ellis, Keith A. Olive, Stefan Pokorski. 1998-11-09. Cosmological Fine Tuning, Supersymmetry, and the Gauge Heirarchy Problem. https://doi.org/10.1016/s0370-2693(99)00168-9

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