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arXiv 1607.08520hep-ph
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具有大质量中介物的隐秘暗物质场景中的遗迹消失

Relic Abundance in a Secluded Dark Matter Scenario with a Massive Mediator

Shohei Okawa, Masaharu Tanabashi, Masato Yamanaka

摘要:

研究了暗物质(DM)粒子$d$的残余丰度,在一个隐蔽的DM方案中,$d$数的减少过程主要不是通过$d$与标准模型粒子的对湮灭,而是通过$dd \to mm$与随后衰变的介质粒子$m$的散射过程.本文指出,即使在质量$m_m$比DM粒子质量$m_d$重到不可忽略的程度的大质量介质中,也可以实现DM的宇宙学观测遗迹丰度。在简并的$d$情形($m_d=m_m$)中,通过调节$dd \to mm$散射振幅足够大,并选择适当的介质粒子寿命,实现了DM残余丰度。早期宇宙中的DM演化表现出典型的“平台”行为,即两步数密度下降行为,第一步存在“假”冻结。在此基础上,提出了一种新的DM模型构建的可能性,即介质粒子$m$与DM粒子$d$统一为近似的暗对称多重态.在可重正化的场论框架下,提出了一个介子DM模型来说明这一思想。

英文摘要:

The relic abundance of the dark matter (DM) particle $d$ is studied in a secluded DM scenario, in which the $d$ number decreasing process dominantly occurs not through the pair annihilation of $d$ into the standard model particles, but via the $dd \to mm$ scattering process with a subsequently decaying mediator particle $m$. It is pointed out that the cosmologically observed relic abundance of DM can be accomplished even with a massive mediator having a mass $m_m$ non-negligibly heavy compared with the DM particle mass $m_d$. In the degenerated $d$-$m$ case ($m_d=m_m$), the DM relic abundance is realized by adjusting the $dd \to mm$ scattering amplitude large enough and by choosing an appropriate mediator particle life-time. The DM evolution in the early universe exhibits characteristic "terrace" behavior, or two-step number density decreasing behavior, having a "fake" freeze-out at the first step. Based on these observations, a novel possibility of the DM model buildings is introduced in which the mediator particle $m$ is unified with the DM particle $d$ in an approximate dark symmetry multiplet. A pionic DM model is proposed to illustrate this idea in a renormalizable field theory framework.

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