三种中微子味的分步光谱交换
Stepwise Spectral Swapping with Three Neutrino Flavors
摘要：
基于密度矩阵理论，我们发展了一个研究集体三味中微子振荡的框架。我们展示了如何证明集体两味中微子振荡，如共转框架有用的技术可以很容易地应用到三味混合。应用两个简单的假设和两个“轻子数”的守恒，我们使用这个框架来演示绝热/进动解是如何出现的。我们用一个数值例子说明了两个逐步光谱交换如何自然出现，如果中微子气体的味道演化可以描述这样的解决方案。对于μ味中微子和τ味中微子均匀混合的特殊情况，我们发现当使用适当的混合参数时，三味中微子和双味中微子的谱交换是一致的.使用共转框架技术，我们展示了如何绝热/进动解决方案，甚至可以在一个占主导地位的普通物质背景的存在下获得。有了这个解决方案，我们可以解释为什么中微子光谱交换可以敏感的偏离最大23-混合时，“μ-τ”的物质项是显着的。
英文摘要：
We develop a framework for studying collective three-flavor neutrino oscillations based on the density matrix formalism. We show how techniques proven useful for collective two-flavor neutrino oscillations such as corotating frames can be applied readily to three-flavor mixing. Applying two simple assumptions and the conservation of two ``lepton numbers'' we use this framework to demonstrate how the adiabatic/precession solution emerges. We illustrate with a numerical example how two stepwise spectral swaps appear naturally if the flavor evolution of the neutrino gas can be described by such a solution. For the special case where mu and tau flavor neutrinos are equally mixed and are produced with identical energy spectra and total numbers, we find that one of the spectral swaps in the three-flavor scenario agrees with that in the two-flavor scenario when appropriate mixing parameters are used. Using the corotating frame technique we show how the adiabatic/precession solution can obtain even in the presence of a dominant ordinary matter background. With this solution we can explain why neutrino spectral swapping can be sensitive to deviations from maximal 23-mixing when the ``mu-tau'' matter term is significant.
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