Naturalizing Supersymmetry with a Two-Field Relaxion Mechanism

TL;DR

This paper introduces a supersymmetric two-field relaxion model that naturally explains supersymmetry tuning, predicts weakly-coupled axion-like particles, and suggests potential dark matter candidates, all while addressing the strong CP problem.

Contribution

It develops a novel supersymmetric relaxion mechanism controlled by a second axion-like field, independent of QCD, and capable of explaining high-scale supersymmetry breaking.

Findings

Relaxion stops rolling at superpartner masses up to 10^9 GeV.

Predicts two weakly-coupled axion-like particles.

Possible existence of an extra Goldstino as dark matter candidate.

Abstract

We present a supersymmetric version of a two-field relaxion model that naturalizes tuned versions of supersymmetry. This arises from a relaxion mechanism that does not depend on QCD dynamics and where the relaxion potential barrier height is controlled by a second axion-like field. During the cosmological evolution, the relaxion rolls with a nonzero value that breaks supersymmetry and scans the soft supersymmetric mass terms. Electroweak symmetry is broken after the soft masses become of order the supersymmetric Higgs mass term and causes the relaxion to stop rolling for superpartner masses up to $\sim 10^9$ GeV. This can explain the tuning in supersymmetric models, including split-SUSY models, while preserving the QCD axion solution to the strong CP problem. Besides predicting two very weakly-coupled axion-like particles, the supersymmetric spectrum may contain an extra Goldstino, which could be a viable dark matter candidate.