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arXiv 1611.04472nucl-thastro-ph.COhep-ph
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不育中微子和额外维对大爆炸核合成的影响

Effects of sterile neutrino and extra-dimension on big bang nucleosynthesis

Dukjae Jang, Motohiko Kusakabe, Myung-Ki Cheoun

备注：
Secs. 2B, 2C, 3, and 4D revised, Fig. 10 added, Figs. 2-13 revised with updated calculations, Appendices A & B added
发表信息：
Phys. Rev. D 97, 043005 (2018)
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摘要：

通过假设大爆炸核合成（BBN）时期存在额外维的无菌中微子，研究了无菌中微子（$ν_{\rm s}$）对BBN的影响，并对与$ν_{\rm s}$性质相关的一些参数进行了约束.首先，对于宇宙膨胀率，我们考虑了五维体和包埋在体中的膜的内禀张力的影响，并通过观测元素丰度来约束额外维度的一个关键参数。其次，考虑了$ν_{\rm s}$在膜上或膜外运动的影响。在这个模型中，$ν_{\rm s}$和活动中微子之间的有效混合角取决于能量，这可能引起混合角的共振效应。因此，在宇宙演化过程中，$ν_{\rm s}$的反应速率会发生剧烈变化。我们通过求解速率方程作为温度的函数来估计$ν_{\rm s}$的丰度和温度，直到无菌中微子去耦。然后，我们发现，残留的$ν_{\rm s}$的丰度大大增强的额外的维度和最大化的特征共振能量$E_{\rm res}\gtrsim 0.01$ GeV。最后，详细讨论了与$ν_{\rm s}$有关的一些约束条件，即混合角和质量差，并将额外维$ν_{\rm s}$修正后的BBN计算结果与轻元素丰度观测数据进行了比较。

英文摘要：

By assuming the existence of extra-dimensional sterile neutrinos in big bang nucleosynthesis (BBN) epoch, we investigate the sterile neutrino ($ν_{\rm s}$) effects on the BBN and constrain some parameters associated with the $ν_{\rm s}$ properties. First, for cosmic expansion rate, we take into account effects of a five-dimensional bulk and intrinsic tension of the brane embedded in the bulk, and constrain a key parameter of the extra dimension by using the observational element abundances. Second, effects of the $ν_{\rm s}$ traveling on or off the brane are considered. In this model, the effective mixing angle between a $ν_{\rm s}$ and an active neutrino depends on energy, which may give rise to a resonance effect on the mixing angle. Consequently, reaction rate of the $ν_{\rm s}$ can be drastically changed during the cosmic evolution. We estimated abundances and temperature of the $ν_{\rm s}$ by solving the rate equation as a function of temperature until the sterile neutrino decoupling. We then find that the relic abundance of the $ν_{\rm s}$ is drastically enhanced by the extra-dimension and maximized for a characteristic resonance energy $E_{\rm res}\gtrsim 0.01$ GeV. Finally, some constraints related to the $ν_{\rm s}$, mixing angle and mass difference, are discussed in detail with the comparison of our BBN calculations corrected by the extra-dimensional $ν_{\rm s}$ to observational data on light element abundances.

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