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arXiv 1104.4807hep-phastro-ph.HE
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在含有轴伴或中性伴LSP的SUSY模型中,允许PQ标度高达M_{GUT}的一些必要条件

Some necessary conditions for allowing the PQ scale as high as M_{GUT} in SUSY models with an axino or neutralino LSP

Howard Baer, Andre Lessa

摘要:

我们研究了在PQMSSM中,无论是轴伴还是中性伴LSP,使Peccei-Quinn标度(f_a)达到超对称大统一尺度(M_{GUT} \sim 10^{16} GeV)所需的条件.在非超对称模型中,由于真空失准的存在,使得具有f_a \sim M_{GUT}的模型中产生了过多的轴子暗物质(\sim f_a^{7/6})。我们指出,一旦包含了轴子超多重态的所有分量,由于轴子衰变的大熵注入,f_a的上限是可以避开的。这种大熵注入也稀释了所有其他准稳定的遗迹密度,自然地避开了BBN约束并解决了引力子问题。我们发现,在剩余密度/BBN约束下,f_a \sim M_{GUT}是允许的,条件是:介子质量m_s> 50 TeV,初始介子场值为PQ量级,初始轴子失准角θ_i \alt为0.05 .对于f_a \sim 10^{15} GeV,这些限制可以大大放宽。再加热温度(T_R)的允许范围在很大程度上取决于LSP的性质。对于轴子LSP,T_R \gtrsim 10^8 GeV,而对于中性子LSP,任何值都是允许的。在后一种情况下,f_a \sim M_{GUT}可以比在axino LSP场景中更容易适应。对于超对称模型中的f_a \sim M_{GUT},暗物质丰度应该由轴子主导,尽管质量m_a \sim为10^{-10} eV,远低于目前实验探测到的区域。

英文摘要:

We examine some conditions which are needed to allow the Peccei-Quinn scale (f_a) as high as the SUSY GUT scale (M_{GUT} \sim 10^{16} GeV) in the context of the PQMSSM with either an axino or a neutralino LSP. The main problem in non-SUSY models with f_a\sim M_{GUT} is the generation of an overabundance of axion dark matter (\sim f_a^{7/6}) due to vacuum misalignment. We show that once all the components of the axion supermultiplet are included, the upper limit on f_a can be evaded due to large entropy injection from saxion decays. This large entropy injection also dilutes all other quasi-stable relic densities, naturally evading the BBN constraints and solving the gravitino problem. We find that f_a\sim M_{GUT} can be allowed by relic density/BBN constraints provided that the saxion mass m_s> 50 TeV, the initial saxion field value is of order of the PQ scale and the initial axion mis-alignment angle θ_i\alt 0.05 . These restrictions can be considerably loosened for f_a\sim 10^{15} GeV. The allowed range for the re-heat temperature (T_R) is strongly dependent on the nature of the LSP. For the axino LSP, T_R \gtrsim 10^8 GeV, while for neutralino LSP any value is allowed. In the latter case, f_a\sim M_{GUT} can be more easily accommodated than in the axino LSP scenario. For f_a\sim M_{GUT} in SUSY models, the dark matter abundance should be dominated by axions, albeit with mass m_a\sim 10^{-10} eV, far below the region currently probed by experiment.

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