Building Models Of Gauge Mediated Supersymmetry Breaking Without A Messenger Sector

TL;DR

The paper proposes a streamlined gauge mediation framework in which the SM gauge interactions directly mediate SUSY breaking from a dynamical SUSY-breaking sector without a separate messenger sector, while preserving perturbative gauge unification. It hinges on a classical flat direction $X$ that is lifted by non-renormalizable superpotential terms, producing $igra F_Xigra ig/ igra Xigra \\sim 10^4$ GeV and a large $igra Xigra$, so SM-charged fields gain mass above $igra Xigra$ without destabilizing unification. A concrete $SU(7) imes SU(6)$ model with an $SU(5)$ global symmetry demonstrates the scheme’s viability by achieving the three goals: perturbative unification, suppressed gravity contributions to sfermion masses, and no need for extremely small couplings; yet a new two-loop RG problem arises when light SM-charged states exist, potentially driving squark/slepton masses negative. The authors argue this issue is model-dependent and propose that viable models avoiding light charged states can be found with further DSB model exploration. Overall, the work provides a principled path toward simpler, direct-coupled GM models with testable phenomenology while highlighting a critical RG caveat that guides future model-building.

Abstract

We propose a general scheme for constructing models in which the Standard Model (SM) gauge interactions are the mediators of supersymmetry breaking to the fields in the supersymmetric SM, but where the SM gauge groups couple directly to the sector which breaks supersymmetry dynamically. Despite the direct coupling, the models preserve perturbative unification of the SM gauge coupling constants. Furthermore, the supergravity contributions to the squark and slepton masses can be naturally small, typically being much less than 1% of the gauge mediated contributions. Both of these goals can be achieved without need of a fine-tuning or a very small coupling constant. This scheme requires run-away directions at the renormalizable level which are only lifted by non-renormalizable terms in the superpotential. To study the proposed scheme in practice, we develop a modified class of models based on $SU(N)\times SU(N-1)$ which allows us to gauge a $SU(N-2)$ global symmetry. However, we point out a new problem which can exist in models where the dynamical supersymmetry breaking sector and the ordinary sector are directly coupled -- the two-loop renormalization group has contributions which can induce negative $(mass)^2$ for the squarks and sleptons. We clarify the origin of the problem and argue that it is likely to be surmountable. We give a recipe for a successful model.