Gauge coupling unification, the GUT scale, and magic fields

TL;DR

This paper introduces special field sets called 'magic' fields that preserve the MSSM's gauge coupling prediction at M_Z while allowing flexible unification scales, aiding GUT model building and beyond.

Contribution

It identifies and analyzes 'magic' fields that maintain one-loop MSSM predictions independently of their mass, offering new tools for GUT and SUSY model construction.

Findings

Magic fields preserve alpha_3(M_Z) prediction regardless of their mass.

They enable flexible GUT scale adjustments without affecting low-energy predictions.

Applications include fixing gauge unification, suppressing KK thresholds, and mediating SUSY breaking.

Abstract

We consider field sets that do not form complete SU(5) multiplets, but exactly preserve the one-loop MSSM prediction for $\alpha_3(M_Z)$ independently of the value of their mass. Such fields can raise the unification scale in different ways, through a delayed convergence of the gauge couplings, a fake unified running below the GUT scale, or a postponed unification after a hoax crossing at a lower scale. The $\alpha_3(M_Z)$ prediction is independent of the mass of the new fields, while the GUT scale often is not, which allows to vary the GUT scale. Such "magic" fields represent a useful tool in GUT model building. For example, they can be used to fix gauge coupling unification in certain two step breakings of the unified group, to suppress large KK thresholds in models with extra dimensions, or they can be interpreted as messengers of supersymmetry breaking in GMSB models.