David Shih

General Gauge Mediation

We give a general definition of gauge mediated supersymmetry breaking which encompasses all the known gauge mediation models. In particular, it includes both models with messengers as well as direct mediation models. A formalism for computing the soft terms in the generic model is presented. Such a formalism is necessary in strongly-coupled direct mediation models where perturbation theory cannot be used. It allows us to identify features of the entire class of gauge mediation models and to distinguish them from specific signatures of various subclasses.

Implications of a 125 GeV Higgs boson for the MSSM and low-scale supersymmetry breaking

Recently, the ATLAS and CMS collaborations have announced exciting hints for a standard model-like Higgs boson at a mass of

Exploring general gauge mediation

\ensuremath{\approx}125\text{ }\text{ }\mathrm{GeV}

Notes on SUSY and R-symmetry breaking in Wess-Zumino models

. In this paper, we explore the potential consequences for the MSSM and low-scale SUSY-breaking. As is well-known, a 125 GeV Higgs implies either extremely heavy stops (

Extra)ordinary gauge mediation

\ensuremath{\gtrsim}10\text{ }\text{ }\mathrm{TeV}

A Complete Model of Low-Scale Gauge Mediation

), or near-maximal stop mixing. We review and quantify these statements, and investigate the implications for models of low-scale SUSY-breaking such as gauge mediation where the

Prompt decays of general neutralino NLSPs at the Tevatron

A

General neutralino NLSPs at the early LHC

-terms are small at the messenger scale. For such models, we find that either a gaugino must be superheavy or the NLSP is long-lived. Furthermore, stops will be tachyonic at high scales. These are very strong restrictions on the mediation of supersymmetry breaking in the MSSM, and suggest that if the Higgs truly is at 125 GeV, viable models of gauge-mediated supersymmetry breaking are reduced to small corners of parameter space or must incorporate new Higgs-sector physics.

Toward Full LHC Coverage of Natural Supersymmetry

We explore various aspects of General Gauge Mediation (GGM). We present a reformulation of the correlation functions used in GGM, and further elucidate their IR and UV properties. Additionally we clarify the issue of UV sensitivity in the calculation of the soft masses in the MSSM, highlighting the role of the supertrace over the messenger spectrum. Finally, we present weakly coupled messenger models which fully cover the parameter space of GGM. These examples demonstrate that the full parameter space of GGM is physical and realizable. Thus it should be considered a valid basis for future phenomenological explorations of gauge mediation.

Surveying extended GMSB models with m h = 125 GeV

We study aspects of Wess-Zumino models related to SUSY and R-symmetry breaking at tree-level. We present a recipe for constructing a wide class of tree-level SUSY and R-breaking models. We also deduce a general property shared by all tree-level SUSY breaking models that has broad application to model building. In particular, it explains why many models of direct gauge mediation have anomalously light gauginos (even if the R-symmetry is broken spontaneously by an order one amount). This suggests new approaches to dynamical SUSY breaking which can generate large enough gaugino masses.