Heavy sterile neutrinos, entropy and relativistic energy production, and the relic neutrino background
Heavy sterile neutrinos, entropy and relativistic energy production, and the relic neutrino background
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重惰性中微子、熵和相对论能量产生以及遗迹中微子背景
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
A. Kusenko
中科院分区：
文献类型：
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作者：
G. Fuller;C. Kishimoto;A. Kusenko
我们探索重中性费米子（例如惰性中微子）的存在对早期宇宙的热历史的影响。特别是，我们考虑静止质量在 100MeV 到 500MeV 范围内的惰性中微子，其与普通活跃中微子的耦合足够大，足以保证早期宇宙温度 T > 1GeV 时的热平衡和化学平衡，但衰变寿命范围可以从几秒到几分钟不等。这种中微子会提前解耦，其残余密度与光子相当，但会失去平衡，从而在大爆炸核合成（BBN）之前或期间产生巨大的熵。大多数惰性中微子静止质量和寿命的范围与宇宙微波背景（CMB）对相对论粒子对能量密度贡献的限制（例如，由内夫参数化）不一致。然而，一些惰性中微子参数可以导致可接受的 Neff。这些参数范围伴随着普通背景残留中微子的相当大的稀释，可能对 BBN 产生不利影响，但有时落在可以解释某些粒子物理模型中测量到的中微子质量的范围内。当这些探测器的检测阈值低于实验室确定的中微子质量值（通过大气中微子振荡尺度确定或通过 KATRIN 或无中微子双 β 衰变实验直接测量）时，这些惰性中微子的强大特征将是测量到的 Neff 6 3 与中微子静止质量没有宇宙学信号相结合。
We explore the implications of the existence of heavy neutral fermions (e.g., sterile neutrinos) for the thermal history of the early universe. In particular, we consider sterile neutrinos with rest masses in the 100MeV to 500MeV range, with couplings to ordinary active neutrinos large enough to guarantee thermal and chemical equilibrium at epochs in the early universe with temperatures T > 1GeV, but in a range to give decay lifetimes from seconds to minutes. Such neutrinos would decouple early, with relic densities comparable to those of photons, but decay out of equilibrium, with consequent prodigious entropy generation prior to, or during, Big Bang Nucleosynthesis (BBN). Most of the ranges of sterile neutrino rest mass and lifetime considered are at odds with Cosmic Microwave Background (CMB) limits on the relativistic particle contribution to energy density (e.g., as parameterized by Neff). However, some sterile neutrino parameters can lead to an acceptable Neff. These parameter ranges are accompanied by considerable dilution of the ordinary background relic neutrinos, possibly an adverse effect on BBN, but sometimes fall in a range which can explain measured neutrino masses in some particle physics models. A robust signature of these sterile neutrinos would be a measured Neff 6 3 coupled with no cosmological signal for neutrino rest mass when the detection thresholds for these probes are below laboratory-established neutrino mass values, either as established by the atmospheric neutrino oscillation scale or direct measurements with, e.g., KATRIN or neutrino-less double beta decay experiments.