Flavor Mediation Delivers Natural SUSY

TL;DR

This paper proposes a novel flavor mediation mechanism linking SM flavor symmetry to SUSY breaking, naturally producing a SUSY spectrum consistent with naturalness, flavor constraints, and gauge unification.

Contribution

It introduces a flavor mediation framework based on gauging the SM's anomaly-free SU(3) flavor symmetry, resulting in a natural SUSY spectrum with specific flavor and mass hierarchies.

Findings

Third-generation scalars are suppressed in mass.

First-two-generation scalars are highly degenerate due to custodial U(2) symmetry.

Predictions for superpartner spectrum are concrete and testable.

Abstract

If supersymmetry (SUSY) solves the hierarchy problem, then naturalness considerations coupled with recent LHC bounds require non-trivial superpartner flavor structures. Such "Natural SUSY" models exhibit a large mass hierarchy between scalars of the third and first two generations as well as degeneracy (or alignment) among the first two generations. In this work, we show how this specific beyond the standard model (SM) flavor structure can be tied directly to SM flavor via "Flavor Mediation". The SM contains an anomaly-free SU(3) flavor symmetry, broken only by Yukawa couplings. By gauging this flavor symmetry in addition to SM gauge symmetries, we can mediate SUSY breaking via (Higgsed) gauge mediation. This automatically delivers a natural SUSY spectrum. Third-generation scalar masses are suppressed due to the dominant breaking of the flavor gauge symmetry in the top direction. More subtly, the first-two-generation scalars remain highly degenerate due to a custodial U(2) symmetry, where the SU(2) factor arises because SU(3) is rank two. This custodial symmetry is broken only at order (m_c/m_t)^2. SUSY gauge coupling unification predictions are preserved, since no new charged matter is introduced, the SM gauge structure is unaltered, and the flavor symmetry treats all matter multiplets equally. Moreover, the uniqueness of the anomaly-free SU(3) flavor group makes possible a number of concrete predictions for the superpartner spectrum.