arXiv 1201.54882012-01-26hep-ph

$E_6$ SSM的现象学方面

Phenomenological Aspects of the $E_6$SSM

Jonathan Peter Hall

备注：: phd thesis

摘要：

惰性中性伴子部门的$E_6$ SSM和暗物质，自然产生于这个部门的研究是第一次。探讨了惰性中性伴子暗物质的实验和宇宙学观测对参数空间的限制，并研究了希格斯玻色子现象学的后果。在合理的情况下，我们发现最轻的惰性中性伴子与类SM的希格斯玻色子的耦合总是相当大。这对希格斯玻色子玻色子对撞机现象学有重大的影响，并导致大的自旋独立的LSP-核子截面。由于后者，$E_6$ SSM惰性中性伴子占所有观测到的暗物质的情况现在受到最近的暗物质直接探测实验分析的严重挑战。在与宇宙学和LEP观测结果相一致的合理假设中，如果最轻的惰性中性伴子对冷暗物质有贡献，那么它的质量必须是Z玻色子质量的一半左右，这意味着$\tan(β)$不能太大。一个新的变种的$E_6$ SSM称为$E_6Z_2^S$ SSM也提出了其中的暗物质的情况是非常不同的惰性中性伴子冷暗物质的情况下，在早期宇宙中的超对称无质量状态的存在下修改宇宙的膨胀率之前大爆炸核合成。新的暗物质方案与当前的观测结果是一致的，修改后的膨胀率比SM预测提供了更好的解释各种数据。还简要讨论了在$E_6$ SSM中暖暗物质的前景。

英文摘要：

The inert neutralino sector of the $E_6$SSM and the dark matter that naturally arises from this sector is studied for the first time. Limits on the parameter space from experimental and cosmological observations relating to the inert neutralino dark matter are explored and the consequences for Higgs boson phenomenology are investigated. In plausible scenarios it is found that the couplings of the lightest inert neutralinos to the SM-like Higgs boson are always rather large. This has major implications for Higgs boson collider phenomenology and leads to large spin-independent LSP-nucleon cross-sections. Because of the latter, scenarios in which $E_6$SSM inert neutralinos account for all of the observed dark matter are now severely challenged by recent dark matter direct detection experiment analyses. In plausible scenarios consistent with observations from both cosmology and LEP the lightest inert neutralino is required to have a mass around half of the Z boson mass if it contributes to cold dark matter and this means that $\tan(β)$ cannot be too large. A new variant of the $E_6$SSM called the $E_6Z_2^S$SSM is also presented in which the dark matter scenario is very different to the inert neutralino cold dark matter scenario and in which the presence of supersymmetric massless states in the early universe modifies the expansion rate of the universe prior to Big Bang Nucleosynthesis. The new dark matter scenario is consistent with current observations and the modified expansion rate provides a better explanation of various data than the SM prediction. The prospects for a warm dark matter scenario in the $E_6$SSM are also briefly discussed.

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