What if Supersymmetry Breaking Unifies beyond the GUT Scale?

TL;DR

This paper explores models where supersymmetry-breaking parameters unify at a scale above the GUT scale, analyzing how this affects sparticle masses and phenomenological regions like coannihilation and focus-point zones.

Contribution

It investigates the impact of unification scale above the GUT scale on supersymmetry-breaking parameter evolution and phenomenological regions in the MSSM.

Findings

Near-degeneracy between neutralino and stau is disfavoured at higher $M_{in}$.

Stau coannihilation region shrinks and can disappear as $M_{in}$ increases.

Focus-point region shifts to larger $m_0$ with increasing $M_{in}$.

Abstract

We study models in which soft supersymmetry-breaking parameters of the MSSM become universal at some unification scale, $M_{in}$, above the GUT scale, $\mgut$. We assume that the scalar masses and gaugino masses have common values, $m_0$ and $m_{1/2}$ respectively, at $M_{in}$. We use the renormalization-group equations of the minimal supersymmetric SU(5) GUT to evaluate their evolutions down to $\mgut$, studying their dependences on the unknown parameters of the SU(5) superpotential. After displaying some generic examples of the evolutions of the soft supersymmetry-breaking parameters, we discuss the effects on physical sparticle masses in some specific examples. We note, for example, that near-degeneracy between the lightest neutralino and the lighter stau is progressively disfavoured as $M_{in}$ increases. This has the consequence, as we show in $(m_{1/2}, m_0)$ planes for several different values of $\tan \beta$, that the stau coannihilation region shrinks as $M_{in}$ increases, and we delineate the regions of the $(M_{in}, \tan \beta)$ plane where it is absent altogether. Moreover, as $M_{in}$ increases, the focus-point region recedes to larger values of $m_0$ for any fixed $\tan \beta$ and $m_{1/2}$. We conclude that the regions of the $(m_{1/2}, m_0)$ plane that are commonly favoured in phenomenological analyses tend to disappear at large $M_{in}$.