轻非热不育中微子的宇宙学约束
Cosmological constraints on a light non-thermal sterile neutrino
摘要：
虽然MiniBooNE实验已经严重限制了轻不育中微子的可能存在，但在振荡数据中仍然存在一些异常，并且额外的轻物质作为次主导热（或暖）成分的可能性仍然很有趣。在许多模型中，这种物质在早期宇宙中处于热平衡状态，与活跃的中微子具有相同的温度，但事实并非如此。在这项工作中，我们拟合了最新的宇宙学数据与扩展的LambdaCDM模型，包括轻文物的质量通常在0.1 - 10 eV的范围内。首先，我们提供了一些几乎与模型无关的约束，其电流密度和速度色散，第二，一些约束，其质量，假设它们包括在早期去耦热遗迹，或在非共振产生的不育中微子。我们的结果可以用来约束大多数粒子物理动机的模型与三个活跃的中微子和一个额外的轻物种。例如，我们发现，在3 σ置信水平下，质量m_s = 2 eV的无菌中微子，只要它是热分布的（T_s/T_nu）< 0.8，或非共振产生的（Delta N_eff）< 0.5，就可以用数据来容纳。当质量增加时，边界变得非常紧。当m_s <0.9eV时，在相同的置信水平下，该数据与标准热化中微子的数据是一致的。
英文摘要：
Although the MiniBooNE experiment has severely restricted the possible existence of light sterile neutrinos, a few anomalies persist in oscillation data, and the possibility of extra light species contributing as a subdominant hot (or warm) component is still interesting. In many models, this species would be in thermal equilibrium in the early universe and share the same temperature as active neutrinos, but this is not necessarily the case. In this work, we fit up-to-date cosmological data with an extended LambdaCDM model, including light relics with a mass typically in the range 0.1 -10 eV. We provide, first, some nearly model-independent constraints on their current density and velocity dispersion, and second, some constraints on their mass, assuming that they consist either in early decoupled thermal relics, or in non-resonantly produced sterile neutrinos. Our results can be used for constraining most particle-physics-motivated models with three active neutrinos and one extra light species. For instance, we find that at the 3 sigma confidence level, a sterile neutrino with mass m_s = 2 eV can be accommodated with the data provided that it is thermally distributed with (T_s/T_nu) < 0.8, or non-resonantly produced with (Delta N_eff) < 0.5. The bounds become dramatically tighter when the mass increases. For m_s < 0.9 eV and at the same confidence level, the data is still compatible with a standard thermalized neutrino.
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