| Budget Amount *help |
¥3,640,000 (Direct Cost: ¥2,800,000、Indirect Cost: ¥840,000)
Fiscal Year 2011: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2010: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000)
Fiscal Year 2009: ¥1,300,000 (Direct Cost: ¥1,000,000、Indirect Cost: ¥300,000)
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| Research Abstract |
Supersymmetric(SUSY) extension of the Standard Model(SM) is widely accepted as the most promising candidate for the physics beyond the SM. However, supersymmetry is broken in the real world. Most of the phenomenological consequences of the SUSY models actually depend on the mechanism of mediating SUSY breaking from the hidden sector to the SM sector. Traditionally, the mechanism of mediating SUSY breaking has been investigated in the bottom up approach by taking various phenomenological requirements as a clue to understand it. Recently, a new category of mechanism to mediate SUSY breaking called“mirage mediation"emerged from the study of effective supergravity theory of superstring and has been gathering a lot of attention. In this project, we tried to extend the concept of the mirage mediation and studied the phenomenology of the mirage mediation taking into account the latest experimental results from the LHC. The main results follow :
1. We analyzed the effective supergravity theory
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of the superstring having the anomalous U(1) gauge symmetry. Depending on the ratio of the contributions to the gauge boson mass from the Stueckelberg mass and the vev of the SM singlet which is introduced to cancel the FI term, the flat direction in the low energy theory varies continuously from the Green-Schwarz(GS) modulus to the SM singlet. Then various combinations of the SUSY breaking mechanism appear in the low energy theory including the mirage mediation which is described as a combination of the modulus mediation and the anomaly mediation.
2. We studied the lepton flavor violating process,μ→eγ, in the minimal SUSY SM(MSSM) with the heavy right-handed neutrino under the mirage mediation. It is found that lepton flavor violation in the mixing terms of the modulus and anomaly mediation is almost cancelled by the threshold correction of the right-handed neutrino, in addition to the lepton flavor violation in the anomaly mediation which is known to be UV insensitive. Then the lepton flavor violation only remains in the modulus mediation contribution.
3. It is known that, in mirage mediation, the SUSY scale one order heavier than the electroweak scale can be realized without any fine-tuning by taking the mirage scale around the TeV scale(TeV scale mirage mediation). Considering the fact that the lower bound of the SUSY particle mass is drastically improved by the LHC and indications of the lightest Higgs boson almost sticking to the upper bound in the MSSM are also reported by the LHC, we investigated the phenomenological consequences when we relax the criteria of the fine-tuning in the TeV scale mirage mediation and push the SUSY scale to 10 TeV. We calculated the relation between the lightest Higgs boson mass and the SUSY scale. Then we found that the measurement of tanβis extremely important to plan the next generation experiments if the SUSY particles is eventually found to be out of the reach of the LHC.
4. Taking into account the above situation introduced by the LHC, we investigated the Next-to-Minimal SUSY SM(NMSSM) in which we add a SM singlet to the MSSM. We examined the structure of the electroweak symmetry breakingand calculated the mass of the lightest Higgs boson. We found that we can rase the effectiveμterm(the higgsino mass) to considerably heavier than the electroweak scale without deteriorating the fine-tuning. This is because of the cancellation between the effectiveμterm and the down-type Higgs boson mass. We also found that the lightest Higgs boson can be as heavy as 125 GeV for 1 Te VSUSY scale simultaneously satisfying the constraint from the false vacuum and the tachyonic mode.
In the middle of the project, the first result from the LHC is published and it suggested that the SUSY particles are much heavier than the expectation when this project is planned, we shifted the emphasis of the study to the study of models with natural heavy SUSY spectrum in mirage mediation from the model building to solve the problem of dark matter over production and the Monte Carlo simulation of SUSY particle production at LHC based on it. The 2nd and 3rd results are still preliminary and we are continuing the studies. We are planning to publish these researches as results of this fund. Less
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