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arXiv 2004.07863hep-phastro-ph.CO
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$U(1)_{\rm B-L}$规范对称性破缺的费米子暗物质

Degenerate Fermion Dark Matter from a Broken $U(1)_{\rm B-L}$ Gauge Symmetry

Gongjun Choi, Motoo Suzuki, Tsutomu. T. Yanagida

备注：
25 pages, 8 figures, 2 tables
发表信息：
Phys. Rev. D 102, 035022 (2020)
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摘要：

通过假设$U(1)_{\rm B-L}$规范对称性来扩展标准模型是非常有动机的，因为它自然地解释了重右手中微子的存在，而重右手中微子的存在是通过跷跷板机制和热轻成因来解释小的活性中微子质量所必需的。传统上，我们引入三个右手中微子来抵消$[U(1)_{\rm B-L}]^3$反常。然而，为了达到这些目的，引入两个重的右手中微子就足够了，因此我们可以用新的手征费米子代替一个右手中微子来消除$U(1)_{\rm B-L}$规范异常。然后，其中一个手征费米子可以自然地扮演暗物质候选者的角色。在本文中，我们演示了如何产生一个暗物质候选人，可以解决所谓的“核心尖点问题”。作为$Λ$ CDM范式遇到的小尺度问题之一，它可能暗示着暗物质性质的重要线索。其中一个解决方案是假设矮球状星系中的亚keV费米子暗物质晕是（准）简并构型。我们展示了如何在我们的模型中，简并的亚keV费米子暗物质候选者可以是非热起源的，因此可以与莱曼- $α$森林观测相一致。因此，小中微子质量，重子不对称性，和sub-keV的暗物质成为破坏的B-L规范对称性的后果。

英文摘要：

The extension of the Standard model by assuming $U(1)_{\rm B-L}$ gauge symmetry is very well-motivated since it naturally explains the presence of heavy right-handed neutrinos required to account for the small active neutrino masses via the seesaw mechanism and thermal leptogenesis. Traditionally, we introduce three right handed neutrinos to cancel the $[U(1)_{\rm B-L}]^3$ anomaly. However, it suffices to introduce two heavy right-handed neutrinos for these purposes and therefore we can replace one right-handed neutrino by new chiral fermions to cancel the $U(1)_{\rm B-L}$ gauge anomaly. Then, one of the chiral fermions can naturally play a role of a dark matter candidate. In this paper, we demonstrate how this framework produces a dark matter candidate which can address the so-called "core-cusp problem". As one of the small scale problems that $Λ$CDM paradigm encounters, it may imply an important clue for a nature of dark matter. One of resolutions among many is hypothesizing that sub-keV fermion dark matter halos in dwarf spheroidal galaxies are in (quasi) degenerate configuration. We show how the degenerate sub-keV fermion dark matter candidate can be non-thermally originated in our model and thus can be consistent with Lyman-$α$ forest observation. Thereby, the small neutrino mass, baryon asymmetry, and the sub-keV dark matter become consequences of the broken B-L gauge symmetry.

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