Mirage mediation reduces the fine-tuning in the minimal supersymmetric standard model by dynamically arranging a cancellation between anomaly-mediated and modulus-mediated supersymmetry breaking. We explore the conditions under which a mirage "messenger scale" is generated near the weak scale and the little hierarchy problem is solved. We do this by explicitly including the dynamics of the SUSY-breaking sector needed to cancel the cosmological constant. The most plausible scenario for generating a low mirage scale does not readily admit an extra-dimensional interpretation. We also review the possibilities for solving the µ/Bµ problem in such theories, a potential hidden source of fine-tuning.Keywords: Supersymmetry Breaking, Supersymmetric Standard Model, Supergravity Models. model (MSSM) is realized in nature has been eroded by the so-called "little hierarchy problem". In the MSSM, the little hierarchy appears as a tension between the two different roles played by the stop squark: on the one hand, the stop should be light to cut off the quadratic divergence in the Higgs boson (mass) 2 and thus minimize fine-tuning; on the other hand, the stop should be heavy enough to generate a physical mass for the Higgs boson above the LEP II bounds. This tension is exacerbated by renormalization group (RG) flow which tends to drive colored particles heavier than electroweak particles. The LEP II bound on charginos, along with the assumption of universal gaugino masses, generically ensures that the stop is quite heavy, requiring fine-tuning at the percent level to achieve successful electroweak symmetry breaking.One potential way to reduce the level of fine-tuning is to have a compressed SUSY spectrum at low scales. Any mechanism yielding such a spectrum while simultaneously evading the bound on the Higgs boson mass merits study. Mirage mediation [1, 2], based on the investigations of [3,4], claims to be such a mechanism. In mirage mediation, a cancellation between modulus mediation [5, 6] and anomaly mediation [7, 8] creates a distinctive low energy SUSY spectrum that appears to unify at a mirage "messenger scale" M mess M GUT . Because this cancellation occurs at every RG scale, there is no hidden fine-tuning between the modulus-and anomaly-mediated contributions [9]. In addition, mirage mediation generically yields large trilinear A terms which generate a large enough physical Higgs mass. Since the leading correction to the Higgs (mass) 2 goes like ∆m 2 Hu = − 3y 2 t 4π 2 m 2 t ln M mess mt , (1.1) the level of fine-tuning can be reduced if M mess is close to the weak scale.
Amorphous SiO2 (a-SiO2) layers were prepared using a thermal oxidation method. The SiO2 layers were nitrided at a temperature Tn between 450 and 650°C utilizing a plasma generation system, in which the layers before the nitridation were simultaneously grown on two different n-type crystalline Si substrates, one having a high resistivity for electron-spin resonance (ESR) and Fourier transform infrared absorption measurements and another having a low resistivity for current–voltage (I–V) measurement. We found the breakdown strength, estimated based on the I–V characteristics, increased with increasing Tn until 550°C, but the annealing at a further high Tn caused also a decrease in the breakdown strength. We found a strong correlation between the changes in the I–V characteristics and those in the bonding properties, and this correlation was also discussed in connection with the change in the ESR properties for the a-SiOxNy layers. Furthermore, incorporation of N atoms into SiO2 layers at Tn=550°C was suggested to improve the structural properties and the electrical properties.
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