Four Generations: SUSY and SUSY Breaking

TL;DR

This paper explores the implications of a fourth generation in supersymmetry, analyzing perturbativity limits and the compatibility with gauge mediated supersymmetry breaking, highlighting constraints and viable parameter regions.

Contribution

It provides a detailed analysis of perturbativity bounds for the fourth generation Yukawa couplings and evaluates the compatibility with gauge mediation models.

Findings

Perturbativity limits are around 1000 TeV for the fourth generation.

Minimal gauge mediation is highly constrained by electroweak symmetry breaking.

A broader gauge mediation framework can better accommodate the fourth generation.

Abstract

We revisit four generations within the context of supersymmetry. We compute the perturbativity limits for the fourth generation Yukawa couplings and show that if the masses of the fourth generation lie within reasonable limits of their present experimental lower bounds, it is possible to have perturbativity only up to scales around 1000 TeV. Such low scales are ideally suited to incorporate gauge mediated supersymmetry breaking, where the mediation scale can be as low as 10-20 TeV. The minimal messenger model, however, is highly constrained. While lack of electroweak symmetry breaking rules out a large part of the parameter space, a small region exists, where the fourth generation stau is tachyonic. General gauge mediation with its broader set of boundary conditions is better suited to accommodate the fourth generation.