Z'-mediated Supersymmetry Breaking

TL;DR

This work investigates SUSY breaking mediated predominantly by an extra $U(1)^\\prime$ gauge interaction, linking the mediation mechanism to the MSSM $\mu$-problem by promoting $\mu$ to a dynamical field via a singlet $S$. The resulting low-energy spectrum exhibits a split-SUSY–like structure with heavy scalars of order $\mathcal{O}(100\ \mathrm{TeV})$ and comparatively light gauginos around $\mathcal{O}(10^2$–$10^3\ \mathrm{GeV})$, plus a SM-like Higgs near $m_h \sim 140\ \mathrm{GeV}$ and a light singlino, with a $Z^\prime$ typically at $\mathcal{O}(10$–$100\ \mathrm{TeV})$; exotic states required for anomaly cancellation are heavy. The authors construct five benchmark models with anomaly-free charges, radiative breaking of $U(1)^\prime$, and spectra obtained from exact RGEs, illustrating varied gaugino/singlino ordering and potential collider signals such as a light $Z^\prime$ in some cases. They discuss implications for gluino lifetimes, dark matter scenarios (including wino-like LSP possibilities), gravitino and neutrino masses, and possible extensions to broader $U(1)^\prime$ symmetries, outlining both experimental signatures and cosmological constraints (e.g., BBN) relevant to this mediation framework.

Abstract

We consider a class of models in which supersymmetry breaking is communicated dominantly via a U'(1) gauge interaction, which also helps solve the μproblem. Such models can emerge naturally in top-down constructions and are a version of split supersymmetry. The spectrum contains heavy sfermions, Higgsinos, exotics, and Z' ~ 10-100 TeV; light gauginos ~ 100-1000 GeV; a light Higgs ~ 140 GeV; and a light singlino. A specific set of U'(1) charges and exotics is analyzed, and we present five benchmark models. Implications for the gluino lifetime, cold dark matter, and the gravitino and neutrino masses are discussed.

Figures (1)

• Figure 1: $Z^\prime$-mediated supersymmetry breaking.