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Register a new userNaturalness-guided Gluino Mass Bound from the Minimal Mixed Mediation of SUSY Breaking
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In order to significantly reduce the fine-tuning associated with the electroweak symmetry breaking in the minimal supersymmetric standard model (MSSM), we consider not only the minimal gravity mediation effects but also the minimal gauge mediation ones for a common supersymmetry breaking source at a hidden sector. In this Minimal Mixed Mediation model, the minimal forms for the Kahler potential and the gauge kinetic function are employed at tree level. The MSSM gaugino masses are radiatively generated through the gauge mediation. Since a focus point of the soft Higgs mass parameter, m_{h_u}^2 appears around 3-4 TeV energy scale in this case, m_{h_u}^2 is quite insensitive to stop masses. Instead, the naturalness of the small m_{h_u}^2 is more closely associated with the gluino mass rather than the stop mass unlike the conventional scenario. As a result, even a 3-4 TeV stop mass, which is known to explain the 125 GeV Higgs mass at three-loop level, can still be compatible with the naturalness of the electroweak scale. On the other hand, the requirements of various fine-tuning measures much smaller than 100 and |mu| < 600 GeV constrain the gluino mass to be 1.6 TeV < M_3 < 2.2 TeV, which is well-inside the discovery potential range of LHC RunII.
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We employ both the minimal gravity- and the minimal gauge mediations of supersymmetry breaking at the grand unified theory (GUT) scale in a single supergravity framework, assuming the gaugino masses are generated dominantly by the minimal gauge mediation effects. In such a minimal mixed mediation model, a focus point of the soft Higgs mass parameter, m_{h_u}^2 emerges at 3-4 TeV energy scale, which is exactly the stop mass scale needed for explaining the 126 GeV Higgs boson mass without the A-term at the three loop level. As a result, m_{h_u}^2 in the MSSM can be quite insensitive to various trial stop masses at low energy, reducing the fine-tuning measures to be much smaller than 100 even for a 3-4 TeV low energy stop mass and -0.5 < A_t / m_0 < +0.1 at the GUT scale. The $mu$ parameter is smaller than 600 GeV. The gluino mass is predicted to be about 1.7 TeV, which could readily be tested at LHC run2.
We employ both the minimal gravity- and the minimal gauge mediations of supersymmetry breaking at the grand unified theory (GUT) scale in a single supergravity framework, assuming the gaugino masses are generated dominantly by the minimal gauge mediation effects. In such a minimal mixed mediation model, a focus point of the soft Higgs mass parameter, m_{h_u}^2 emerges at 3-4 TeV energy scale, which is exactly the stop mass scale needed for explaining the 126 GeV Higgs boson mass without the A-term at the three loop level. As a result, m_{h_u}^2 can be quite insensitive to various trial stop masses at low energy, reducing the fine-tuning measures to be much smaller than 100 even for a 3-4 TeV low energy stop mass and -0.5 < A_t/m_0 < +0.1 at the GUT scale. The gluino mass is predicted to be about 1.7 TeV, which could readily be tested at LHC run2.
Supersymmetry breaking in a metastable vacuum allows one to build simple and concrete models of gauge mediation. Generation of gaugino masses requires that R-symmetry be broken in this vacuum. In general, there are two possible ways to break R-symmetry, explicitly or spontaneously. We find that the MSSM phenomenology depends crucially on how this breaking occurs in the Hidden Sector. Explicit R-symmetry breaking models can lead to fairly standard gauge mediation, but we argue that in the context of ISS-type models this only makes sense if B=0 at the mediation scale, which leads to high tan(beta). If on the other hand, R-symmetry is broken spontaneously, then R-symmetry violating soft terms tend to be suppressed with respect to R-symmetry preserving ones, and one is led to a scenario with large scalar masses. These models interpolate between standard gauge mediation and split SUSY models. We provide benchmark points for the two scenarios. They demonstrate that the specific dynamics of the Hidden Sector -- the underlying nature of supersymmetry and R-symmetry breaking -- affects considerably the mass spectrum of the MSSM, and vice versa.
Recent progress in realising dynamical supersymmetry breaking allows the construction of simple and calculable models of gauge mediation. We discuss the phenomenology of the particularly minimal case in which the mediation is direct, and show that there are generic new and striking predictions. These include new particles with masses comparable to those of the Standard Model superpartners, associated with the pseudo-Goldstone modes of the dynamical SUSY breaking sector. Consequently there is an unavoidable departure from the MSSM. In addition the gaugino masses are typically significantly lighter than the sfermions, and their mass ratios can be different from the pattern dictated by the gauge couplings in standard (i.e. explicit) gauge mediation. We investigate these features in two distinct realisations of the dynamical SUSY breaking sector.
We consider a scenario where the supersymmetry breaking and its mediation, and the cancellation of the theta parameter of SU(3)c are all caused by a single chiral multiplet. The string axion multiplet is a natural candidate of such a single superfield. We show that the scenario provides a convincing basis of focus point gaugino mediation, where the electroweak scale is explained with a moderate tuning among the parameters of the theory.
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