Du, G (reprint author), Chinese Acad Sci, State Key Lab Theoret Phys, Beijing 100190, Peoples R China.
We point out that the electroweak fine-tuning problem in the supersymmetric standard models (SSMs) is mainly due to the high energy definition of the fine-tuning measure. We propose supernatural supersymmetry which has an order one high energy fine-tuning measure automatically. The key point is that all the mass parameters in the SSMs arise from a single supersymmetry breaking parameter. In this paper, we show that there is no supersymmetry electroweak fine-tuning problem explicitly in the minimal SSM (MSSM) with no-scale supergravity and Giudice-Masiero mechanism. We demonstrate that the Z-boson mass, the supersymmetric Higgs mixing parameter mu at the unification scale, and the sparticle spectrum can be given as functions of the universal gaugino mass M-1/2. Because the light stau is the lightest supersymmetric particle (LSP) in the no-scale MSSM, to preserve R parity, we introduce a non-thermally generated axino as the LSP dark matter candidate. We estimate the lifetime of the light stau by calculating its two-body and three-body decays to the LSP axino for several values of axion decay constant f(a), and find that the light stau has a lifetime tau((tau) over bar1) in [10(-4), 100] s for an f(a) range [10(9), 10(12)] GeV. We show that our next to the LSP stau solutions are consistent with all the current experimental constraints, including the sparticle mass bounds, B-physics bounds, Higgs mass, cosmological bounds, and the bounds on long-lived charged particles at the LHC.
Natural Science Foundation of China [10821504, 11075194, 11135003, 11275246, 11475238]
; National Basic Research Program of China (973 Program) [2010CB833000]
; U.S. Department of Energy Award [DE-FG03-95-ER-40917]