Gauge Coupling Unification in MSSM + 5 Flavors

TL;DR

This paper analyzes gauge coupling unification in the MSSM extended with five vectorlike flavors, identifying parameter space regions where unification occurs and establishing bounds on flavor masses.

Contribution

It provides a detailed 2-loop analysis of unification in MSSM with extra flavors, establishing bounds on flavor masses for successful unification.

Findings

Unification only occurs in specific parameter regions.

Lower bounds on flavor masses are established.

Models near the boundary have unreliable unification predictions.

Abstract

We investigate gauge coupling unification at 2-loops for theories with 5 extra vectorlike SU(5) fundamentals added to the MSSM. This is a borderline case where unification is only predicted in certain regions of parameter space. We establish a lower bound on the scale for the masses of the extra flavors, as a function of the sparticle masses. Models far outside of the bound do not predict unification at all (but may be compatible with unification), and models outside but near the boundary cannot reliably claim to predict it with an accuracy comparable to the MSSM prediction. Models inside the boundary can work just as well as the MSSM.