Felix Brümmer

Anatomy of maximal stop mixing in the MSSM

A bstractA Standard Model-like Higgs near 125 GeV in the MSSM requires multi-TeV stop masses, or a near-maximal contribution to its mass from stop mixing. We investigate the maximal mixing scenario, and in particular its prospects for being realized it in potentially realistic GUT models. We work out constraints on the possible GUT-scale soft terms, which we compare with what can be obtained from some well-known mechanisms of SUSY breaking mediation. Finally, we analyze two promising scenarios in detail, namely gaugino mediation and gravity mediation with non-universal Higgs masses.

Approximate R-symmetries and the μ term

We discuss the role of approximate U(1)R symmetries for the understanding of hierarchies in Nature. Such symmetries may explain a suppressed expectation value of the superpotential and provide us with a solution to the MSSM μ problem. We present various examples in field theory and string-derived models.

Phenomenology of supersymmetric Gauge-Higgs unification

Supersymmetric Gauge-Higgs Unification is a well-motivated new physics scenario, both in heterotic model building and from the perspective of higher-dimensional Grand Unified Theories. When combined with radion mediated supersymmetry breaking, it allows for very specific predictions concerning the high-scale parameters of the MSSM. Using an appropriately modified version of a standard RGE evolution code (SuSpect), we derive low-scale predictions which can be tested at the LHC. The phenomenological success of our setting depends crucially on the 5d Chern-Simons term, which has not been used in previous, less encouraging studies of gauge-Higgs unification in supersymmetry.

Focus point gauge mediation in product group unification

Abstract In certain models of gauge-mediated supersymmetry breaking with messenger fields in incomplete GUT multiplets, the radiative corrections to the Higgs potential cancel out during renormalization group running. This allows for relatively heavy superpartners and for a 125 GeV Higgs while the fine-tuning remains modest. In this Letter, we show that such gauge mediation models with “focus point” behaviour can be naturally embedded into a model of SU ( 5 ) × U ( 3 ) product group unification.

The supersymmetric flavour problem in 5D GUTs and its consequences for LHC phenomenology

A bstractWe study supersymmetric models with a GUT-sized extra dimension, where both the Higgs fields and the SUSY breaking hidden sector are localized on a 4D brane. Exponential wave function profiles of the matter fields give rise to hierarchical structures in the Yukawa couplings and soft terms. Such structures can naturally explain hierarchical fermion masses and mixings, while at the same time alleviating the supersymmetric flavour problem. We discuss two sources of supersymmetry breaking, radion mediation and brane fields, and perform a detailed numerical analysis, thoroughly taking into account the proliferation of unknown

Metastable supersymmetry breaking without scales

\mathcal{O}

The Fermi scale as a focus point of high-scale gauge mediation

(1) coefficients that occurs in this class of models. It turns out that additional assumptions on supersymmetry breaking are necessary to evade the stringent experimental bounds on lepton flavour violation. The favourable regions of parameter space are then examined with regards to their LHC phenomenology. They generically feature heavy gluinos and squarks beyond current bounds. Lepton flavour violation in SUSY cascade decays can give interesting signatures.

Magnetic mixing — electric minicharges from magnetic monopoles

Certain supersymmetric grand unified models predict that the coefficients of the quadratic terms in the MSSM Higgs potential,