A new approach to Naturalness in SUSY models

TL;DR

This paper introduces a model-independent approach to naturalness in SUSY models, linking fine-tuning directly to the likelihood of data fit, which challenges the viability of popular supersymmetric theories.

Contribution

It proposes a new, objective method to assess naturalness in SUSY models by integrating fine-tuning into the likelihood function, avoiding subjective definitions.

Findings

Naturalness is intrinsic to the likelihood of data fit.

Imposing the EW scale constraint reduces models' likelihood.

Current SUSY models face viability issues under this new approach.

Abstract

We review recent results that provide a new approach to the old problem of naturalness in supersymmetric models, without relying on subjective definitions for the fine-tuning associated with {\it fixing} the EW scale (to its measured value) in the presence of quantum corrections. The approach can address in a model-independent way many questions related to this problem. The results show that naturalness and its measure (fine-tuning) are an intrinsic part of the likelihood to fit the data that {\it includes} the EW scale. One important consequence is that the additional {\it constraint} of fixing the EW scale, usually not imposed in the data fits of the models, impacts on their overall likelihood to fit the data (or chi^2/ndf, ndf: number of degrees of freedom). This has negative implications for the viability of currently popular supersymmetric extensions of the Standard Model.