arXiv 1702.033322017-02hep-ph

中微子在物质中生存概率的有效双味近似

An Effective Two-Flavor Approximation for Neutrino Survival Probabilities in Matter

Hisakazu Minakata

备注：: Discussion on appearance effective $Δm^2$ added. Version to appear in JHEP. 26 pages, 3 figures
DOI：: 10.1007/JHEP05(2017)043

摘要：

已知在真空中，在中微子能量$E$和基线$L$的区域中，通过引入有效$Δm^2_{αα}$（$α= e, μ, τ$），三味中微子的存活概率可以由有效双味形式近似到$ε\equiv Δm^2_{21} / Δm^2_{31}$中的一阶，使得$Δm^2_{31} L / 2E \sim π$。在这里，我们调查的问题是否类似的有效的两味近似可以制定的生存概率的问题。利用一个具有展开参数$ε$和$s_{13} \propto \sqrtε$的微扰框架，我们对这个问题给出了肯定的回答，并且由此得到的概率的双味形式对$ε$是有效的.然而，我们观察到物质中有效的$Δm^2_{αα} (a)$的人为特征。它不再是基本参数的组合，而是具有能量依赖性，这可能是合理的，因为它来自物质势。但是，事实证明，$Δm^2_{μμ} (a)$成为$L$依赖性的，虽然$Δm^2_{ee} (a)$不是，这对有效$Δm^2$的概念在物质上的适当性提出了怀疑。我们还发现，在真空中的出现概率承认，为了$ε$，类似的有效的两味形式与一个略有不同的有效$Δm^2_{βα}$从消失的渠道。一个一般的结果，推导出描述的振荡概率的物质效应的抑制。

英文摘要：

It is known in vacuum that the three-flavor neutrino survival probability can be approximated by the effective two-flavor form to first orders in $ε\equiv Δm^2_{21} / Δm^2_{31}$, with introduction of the effective $Δm^2_{αα}$ ($α= e, μ, τ$), in regions of neutrino energy $E$ and baseline $L$ such that $Δm^2_{31} L / 2E \sim π$. Here, we investigate the question of whether the similar effective two-flavor approximation can be formulated for the survival probability in matter. Using a perturbative framework with the expansion parameters $ε$ and $s_{13} \propto \sqrtε$, we give an affirmative answer to this question and the resultant two-flavor form of the probability is valid to order $ε$. However, we observe a contrived feature of the effective $Δm^2_{αα} (a)$ in matter. It ceases to be a combination of the fundamental parameters and has energy dependence, which may be legitimate because it comes from the matter potential. But, it turned out that $Δm^2_{μμ} (a)$ becomes $L$-dependent, though $Δm^2_{ee} (a)$ is not, which casts doubt on adequacy of the concept of effective $Δm^2$ in matter. We also find that the appearance probability in vacuum admits, to order $ε$, the similar effective two-flavor form with a slightly different effective $Δm^2_{βα}$ from the disappearance channel. A general result is derived to describe suppression of the matter effect in the oscillation probability.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

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