arXiv 1908.098412019-08hep-phastro-ph.COastro-ph.HEhep-th

暗物质与自然性

Dark Matter and Naturalness

Mark P. Hertzberg, McCullen Sandora

备注：: 32 pages, 3 figures. V2: Further clarifications; updated towards version published in JHEP
发表信息：: JHEP 12 (2019) 037
DOI：: 10.1007/JHEP12(2019)037

摘要：

粒子物理学的标准模型是由庞加莱对称性所支配的，而所有其他的对称性，无论是精确的还是近似的，本质上都是由与粒子谱的理论一致性所决定的。另一方面，存在许多暗物质的模型，它们依赖于新增加的全局对称性的增加，以便稳定暗物质粒子和/或实现正确的丰度。在这项工作中，我们开始系统地探索真正的自然模型的暗物质，组织只有相对论和量子力学，没有呼吁任何额外的全球对称性，没有微调，没有小参数。我们首先回顾如何基于自旋0或自旋${1\over2}$的单重态暗扇区应该很容易衰减，而纯强耦合自旋1模型有一个过剩的问题。这就不可避免地导致我们构建自旋${1\over2}$粒子在自旋1粒子约束下带电的手征模型。这导致了稳定的暗物质候选者，它们是重子的类似物，具有自然$\mathcal{O}(100)$ TeV的限制尺度。这导致了正确的冻结出丰度湮灭成无质量的无约束暗费米子。极小模型包含$SU(3)\times SU(2)$的暗拷贝和1代手征暗夸克和轻子。无质量暗轻子的存在有可能在BBN过程中产生较大的$ΔN_{\text{eff}}$值。为了不扰乱BBN，人们可以求助于标准模型之外的大量重自由度，或者假设暗扇区比可见扇区具有更低的再热温度，这在这个框架中也是自然的。这种推理提供了一套完全自然的暗物质模型。有些是噩梦般场景的具体实现，其中暗物质可能非常难以检测，这可能会影响未来的搜索技术。

英文摘要：

The Standard Model of particle physics is governed by Poincaré symmetry, while all other symmetries, exact or approximate, are essentially dictated by theoretical consistency with the particle spectrum. On the other hand, many models of dark matter exist that rely upon the addition of new added global symmetries in order to stabilize the dark matter particle and/or achieve the correct abundance. In this work we begin a systematic exploration into truly natural models of dark matter, organized by only relativity and quantum mechanics, without the appeal to any additional global symmetries, no fine-tuning, and no small parameters. We begin by reviewing how singlet dark sectors based on spin 0 or spin ${1\over2}$ should readily decay, while pure strongly coupled spin 1 models have an overabundance problem. This inevitably leads us to construct chiral models with spin ${1\over2}$ particles charged under confining spin 1 particles. This leads to stable dark matter candidates that are analogs of baryons, with a confinement scale that can be naturally $\mathcal{O}(100)$TeV. This leads to the right freeze-out abundance by annihilating into massless unconfined dark fermions. The minimal model involves a dark copy of $SU(3)\times SU(2)$ with 1 generation of chiral dark quarks and leptons. The presence of massless dark leptons can potentially give rise to a somewhat large value of $ΔN_{\text{eff}}$ during BBN. In order to not upset BBN one may either appeal to a large number of heavy degrees of freedom beyond the Standard Model, or to assume the dark sector has a lower reheat temperature than the visible sector, which is also natural in this framework. This reasoning provides a robust set of dark matter models that are entirely natural. Some are concrete realizations of the nightmare scenario in which dark matter may be very difficult to detect, which may impact future search techniques.

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英文摘要：

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