Fine-tuned vs. natural supersymmetry: what does the string landscape predict?

TL;DR

This paper investigates how the string landscape influences the likelihood of different supersymmetry models, suggesting that natural SUSY models are more probable than unnatural ones based on environmental considerations and probability measures.

Contribution

It introduces a scheme to compute the relative probabilities of supersymmetric models emerging from the string landscape, favoring natural SUSY models over unnatural ones.

Findings

Landscape favors softly broken supersymmetric models.

Probabilities relate to the weak scale within the atom-forming window.

Natural SUSY models are more probable than unnatural models.

Abstract

A vast array of (metastable) vacuum solutions arise from string compactifications, each leading to different 4-d laws of physics. The space of these solutions, known as the string landscape, allows for an environmental solution to the cosmological constant problem. We examine the possibility of an environmental solution to the gauge hierarchy problem. We argue that the landscape favors softly broken supersymmetric models over particle physics models containing quadratic divergences, such as the Standard Model. We present a scheme for computing relative probabilities for supersymmetric models to emerge from the landscape. The probabilities are related to the likelihood that the derived value of the weak scale lies within the Agrawal et al. (ABDS) allowed window of values leading to atoms as we know them. This then favors natural SUSY models over unnatural (SUSY and other) models via a computable probability measure.