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arXiv 2503.21998hep-ph
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大爆炸核合成作为非标准中微子相互作用和非幺正三中微子混合的探针

Big Bang Nucleosynthesis as a probe of non-standard neutrino interactions and non-unitary three-neutrino mixing

Gabriela Barenboim, Stefano Gariazzo, Alberto Sánchez-Vargas

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22 pages, 5 figures, 1 table. Version accepted for publication in JCAP
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AI总结：

本研究探讨非标准中微子相互作用和非幺正三中微子混合对早期宇宙观测量的影响，发现BBN约束严格且与地面实验相当，并强调需更多核反应率测量以改进理论预测。

摘要：

在这项工作中，我们研究了两种关于中微子在早期宇宙中作用的唯象超标准模型（BSM）情景的影响：非标准中微子相互作用（NSI）和非幺正三中微子混合。我们评估了这些框架对两个关键宇宙学观测量的影响：与中微子脱耦相关的相对论性中微子物种的有效数目（\Neff），以及大爆炸核合成（BBN）中产生的轻元素丰度。首次在BBN背景下研究了中微子与夸克的带电流非标准相互作用（CC-NSI）和非幺正三中微子混合，并发现对此类相互作用的约束非常严格。特别是，对于非对角CC-NSI参数$\varepsilon^{udV}_{e α}$（其中$α\neq e$）和非幺正参数$α_{22}$，BBN的限制与地面实验得出的限制具有竞争力。在非幺正情况下，中微子脱耦与BBN的结合施加了严格的约束，这些约束可以轻微地偏向于新物理（NP）的存在，或加强标准模型（SM），具体取决于BBN计算中所涉及的实验核反应率的选择。这些结果强调了已经指出的需要进一步测量核反应率以获得更稳健的BBN理论预测的必要性。

英文摘要：

In this work we investigate the impact of two phenomenological Beyond the Standard Model (BSM) scenarios concerning the role of neutrinos in the early universe: non-standard neutrino interactions (NSI) and non-unitary three-neutrino mixing. We evaluate the impact of these frameworks on two key cosmological observables: the effective number of relativistic neutrino species (\Neff), related to neutrino decoupling, and the abundances of light elements produced at Big Bang Nucleosynthesis (BBN). For the first time, neutrino CC-NSI with quarks and non-unitary three-neutrino mixing are studied in the context of BBN, and the constraints on such interactions are found to be remarkably restrictive. In particular, the BBN limits are competitive with the ones derived from terrestrial experiments for the non-diagonal CC-NSI parameter $\varepsilon^{udV}_{e α}$, with $α\neq e$ and for the non-unitarity parameter $α_{22}$. In the case of non-unitarity, the combination between neutrino decoupling and BBN imposes stringent constraints that can either mildly favour the existence of New Physics (NP), or reinforce the SM, depending on the choice of the experimental nuclear rates involved in the BBN calculation. These results stress the already noted need for further nuclear rates measurements in order to obtain more robust BBN theoretical predictions.

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