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arXiv 2103.05648hep-phastro-ph.CO
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具有可观测$Δ{N_{\rm eff}}$的轻狄拉克中微子入口暗物质

Light Dirac neutrino portal dark matter with observable $Δ{N_{\rm eff}}$

Anirban Biswas, Debasish Borah, Dibyendu Nanda

备注：
39 pages, 7 figures, 1 table, a new discussion related to the decay of $ϕ$ has been added in Appendix A, new figures are added, new references are added, conclusion remains unchanged, version accepted for publication in JCAP
发表信息：
JCAP 10 (2021) 002
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摘要：

我们提出了一个狄拉克中微子门户暗物质的方案，通过最小限度地扩展的标准模型（SM）的粒子内容与三个右手中微子（$ν_R$），狄拉克费米子暗物质候选者（$ψ$）和一个复杂的标量（$ϕ$），所有这些都是在SM规范群下的单线态。为了保证暗物质候选粒子$ψ$的稳定性，同时也保证了轻中微子的狄拉克性质，引入了额外的$\mathbb{Z}_4$对称性。右手中微子和暗物质都与SM等离子体热化，这是由于涉及$ν_R$、$ψ$和$ϕ$的新的汤川相互作用，而后者通过希格斯门相互作用保持热接触。当$ϕ$失去其与SM等离子体的动力学平衡时，$ν_R$的去耦发生，并且此后所有三个$\mathbb{Z}_4$带电粒子在它们之间形成具有温度$T_{ν_R}$的平衡。候选的暗物质$ψ$最终冻结在暗区，并保留了其丰富的遗迹。我们已经发现，在目前的情况下，一部分低质量暗物质（$M_ψ\lesssim10$ GeV）已经被普朗克2018年的数据排除在外，用于将$ν_R$保持在低于600 MeV的温度下的热浴中，从而对$N_{\rm eff}$产生额外的贡献。CMB-S4、SPT-3G等下一代实验将具有所需的灵敏度来探测这种最小场景的整个模型参数空间，特别是$ψ$的低质量范围，其中直接检测实验仍然不足以进行检测。

英文摘要：

We propose a Dirac neutrino portal dark matter scenario by minimally extending the particle content of the Standard Model (SM) with three right handed neutrinos ($ν_R$), a Dirac fermion dark matter candidate ($ψ$) and a complex scalar ($ϕ$), all of which are singlets under the SM gauge group. An additional $\mathbb{Z}_4$ symmetry has been introduced for the stability of dark matter candidate $ψ$ and also ensuring the Dirac nature of light neutrinos at the same time. Both the right handed neutrinos and the dark matter thermalise with the SM plasma due to a new Yukawa interaction involving $ν_R$, $ψ$ and $ϕ$ while the latter maintains thermal contact via the Higgs portal interaction. The decoupling of $ν_R$ occurs when $ϕ$ loses its kinetic equilibrium with the SM plasma and thereafter all three $\mathbb{Z}_4$ charged particles form an equilibrium among themselves with a temperature $T_{ν_R}$. The dark matter candidate $ψ$ finally freezes out within the dark sector and preserves its relic abundance. We have found that in the present scenario, some portion of low mass dark matter ($M_ψ\lesssim10$ GeV) is already excluded by the Planck 2018 data for keeping $ν_R$s in the thermal bath below a temperature of 600 MeV and thereby producing an excess contribution to $N_{\rm eff}$. The next generation experiments like CMB-S4, SPT-3G etc. will have the required sensitivities to probe the entire model parameter space of this minimal scenario, especially the low mass range of $ψ$ where direct detection experiments are still not capable enough for detection.

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